US Botanic Garden Presents The Latest Poinsettia Varieties

One of many beautiful poinsettias at the US Botanic Garden

I’ve been to the US Botanic Garden (USBG) many times and have always enjoyed the beautiful displays that change with the seasons. But in December, I bypass the holiday dazzle of the evergreen-draped lobby, work my way through the steamy medicinal plant and orchid gardens and head straight to the restrooms. There, behind the glass atrium in a quiet passage all its own is the USBG’s best-kept secret: a one-of-a-kind poinsettia display.

And the collection grows year after year to include an increasing array of spectacular varieties. Sharing the limelight with the traditional reds are the latest, eye-catching hybrids in bright white, soft yellow, light pink and salmon. There are marbled varieties, spotted ones and some that are the result of crossbreeding with other species (more on that below.)

US Botanic Garden poinsettia passage

The effect is of a rich winter garden filled with unusual, multi-colored flowers. Luckily there are benches just across on which a visitor can sit back and take it all in.

The leaf is not the flower

It’s important to note, when looking at a poinsettia, that it’s the bracts (modified leaves) that provide the color. The real blooms are the tiny yellow buds called cyathia in the center. Once the flowers have shed their pollen, the plant drops its bracts and leaves. Because of this, it’s always good when shopping for a poinsettia to select a plant with little or no pollen showing.

Poinsettia flowers are yellow

Poinsettias are referred to as a short-day photoperiod crop, meaning they naturally flower once the nights become longer. To create their colored bracts, the plants require at least 12 hours at a time of darkness over a period of at least five days in a row. Once they have completed the process, however, poinsettias require bright sunlight during the day to attain the brightest color.

Once considered a weed

In its native Mexico, the poinsettia is a perennial flowering shrub or small tree that typically grows to a height of 10 to 15 feet. A member of the spurge family, it goes by the botanical name Euphorbia pulcherrima. Poinsettia shrubs were once considered weeds. Today they are the best selling potted plant in the United States and Canada, with more than 100 varieties available.

A poinsettia shrub as it might appear in the wild

The Dogwood poinsettia, Euphorbia cornastra, was first discovered in 1973 growing in the high elevation tropical forests of Mexico. Although similar in growth habit and inflorescence to Euphorbia pulcherrima, it has gray-green foliage and is summer flowering. Dogwood poinsettia is prized for its pure-white bracts. This year’s USBG display includes a stunning example.

Dogwood poinsettia, Euphorbia conastra

Close-up of Euphorbia conastra’s brilliant white inflorescence

White varieties followed traditional red

The first white poinsettia varieties were introduced in the 1970s. Since then, there have been many improvements. An example is Euphorbia ‘Princettia Pure White’, which features pure white bracts and barely visible flowers. The Princettia series has a unique bract form whose blooms mature early, resulting in a more clean-looking ‘flower.’

Cross-breeding has spawned an array of new colors

Growers have been tinkering with hybrid poinsettias for some time now, making the plants more compact and increasing their longevity. The past five years, though, have seen a surge in cross-breeding specifically to produce unconventional colors. The new hues are created by crosses between poinsettia and other euphorbia species.

‘Luv U Pink’ is one such variety produced by the Paul Ecke Ranch for Breast Cancer Awareness. Its hot pink bracts have a thin, pale pink edge. The bracts have an otherworldly iridescent shimmer.

Euphorbia ‘Luv U Pink’

A newer variety incorporates a white splash.

Euphorbia ‘Luv U Pink Splash’

You can’t lose these marbles

The marbled varieties, first pioneered in the 1970s, provide a spectacular contrast to the traditional reds. I love their painterly quality, almost as if someone has splashed them with a brush.

Euphorbia ‘Red Glitter’

Euphorbia ‘Peppermint Ruffles’

Euphorbia ‘Christmas Feelings Red Cinnamon’

Euphorbia ‘Ice Punch

Pretty in pink

Then there are the soft pink varieties, which provide a quiet respite from all the bright hues. Among them, these three are standouts:

Euphorbia ‘Luv U Soft Pink’

Euphorbia ‘Princettia Pink’

Euphorbia ‘Autumn Leaves’

Back to basics

Of course, traditional red still makes up the bulk of the sales, with growers hesitant to spend the time and money it takes to develop too many new varieties. Usually they choose just a couple to focus on and leave the rest of their energy for the reds. Below, USBG’s 2017 display includes Euphorbia ‘Jester Red’, Euphorbia ‘St. Louis’ (shrub) and a beautiful rose-shaped variety called Euphorbia ‘Winter Rose Early Red’.

Traditional reds: Euphorbias ‘Jester Red, ‘St. Louis’ and ‘Winter Rose Early Red’

Close-up of Euphorbia ‘Winter Rose Early Red’

Before you go rushing to the nursery (as I did) to purchase some of these gorgeous new varieties, though, it’s worth noting that many are not yet commercially available. Still, I was delighted to find two varieties of the marbled ‘Jingle Bells’ at my local grower. Here’s hoping more hybrids will come onto the market in the coming years.

For more information on poinsettias’ namesake, Ambassador Joel Roberts Poinsett, and how the plant came to be so famous, click here for my blog post on the Paul Ecke Ranch.



Top Holiday Plants And How To Keep Them Blooming

Soon, many of us will be receiving gifts of holiday plants with no clue what to do with them. Sure, the seasonal blooms look great in their decorative wrappings, but too often, just one week later they’re already showing signs of distress. Why toss these beauties in the trash when there’s still so much floral potential? Here’s how to keep your holiday plants looking their best and blooming well past the holiday season.


The best thing you can do for your holiday plant is to remove its decorative wrapper. All plants need good drainage to maintain good health. Foil wrappers and containers without drainage holes prevent water from escaping, meaning your holiday plant will sit in water every time you water it. You might have noticed the signs – yellowing leaves and sagging flowers? Since waterlogged soils leave little space for oxygen, the roots start to rot and very soon after, the plant dies.



I love receiving gifts of this beautiful succulent. The tiny clusters of orange, yellow, red or pink flowers remain attractive for weeks and the deep green, glossy foliage provides a dramatic backdrop. It’s crucial, though, to remove the container when watering. Succulents need good drainage and will rot if they receive too much water.

No forced blooms here — kalanchoes naturally bloom indoors during winter and early spring. Place your gift in bright light so it can receive at least 2 hours of sun, and water it every 2 weeks when the top of the soil feels dry. Keep it away from drafty doors and windows, which will spell the death of this holiday plant.



My house is often filled with cyclamens at holiday time. I love the plant’s upswept, fluttery petals and deep green variegated leaves. Florist cyclamens have been bred over more than 150 years, and today there are many new colors, petal shapes, sizes and fragrances to choose from.

Cyclamens can be pretty temperamental, though. Since they prefer cooler temperatures (below 70°F is ideal), their leaves will yellow and their flowers will droop if they get too hot. The plants are also very sensitive to watering — both too little and too much water will cause much the same effect. To keep your holiday plant in shape, remove it from its wrapper or container and water thoroughly only when the soil surface feels dry to the touch. Take care not to let any water touch the sensitive leaves or flower stems. After the plant has drained thoroughly, return it to its container.



These gorgeous tropical flowering plants are known for their bright red, heart-shaped ‘flowers’ which are actually spathes, or a kind of leaf that grows from the base of a spike of flowers. (Anthurium flowers are the yellow spike in the middle.) What makes this holiday plant special is that with proper care, it can remain in almost continuous flower for weeks, with some blooms lasting two months or more.

Anthuriums grow best in medium to bright light (avoid direct sunlight, however.) Keep the soil consistently moist and for best results, use tepid water when watering. A consistently warm temperature is key to keeping this holiday plant looking its best, so avoid placing it near drafty doors or windows.

Phalaenopsis Orchid

Phalaenopsis orchid

Of course there are thousands of varieties of orchids to choose from, but most orchid gifts come in the form of the easy-to-grow Phalaenopsis (also known as the Moth orchid), which can bloom for up to 3 months. The plant flourishes indoors under normal lighting conditions and prefers the same temperatures that humans do.

Place your orchid in indirect sunlight and water once a week, making sure the soil remains moist just under the soil surface. Be careful not to overwater or the flowers will wilt and fall off. Orchids need good air circulation around the roots to prevent root rot, so make sure your decorative container leaves plenty of room for the plant to breath. And always remove the plant from its container when watering, returning it only after it has drained completely.

Christmas Cactus

Pink-blooming Christmas cactus

This beautiful flowering plant loves holidays. There are Thanksgiving, Christmas and Easter varieties. Some bloom at Christmas and then again at Easter with proper care. Most times, people don’t know which kind they’re gifting, so your cactus may or may not rebloom after the initial holiday flush.

Christmas cacti thrive in bright, indirect light and cool temperatures, away from drafts and heat sources that can stunt growth and burn leaves. Christmas cactus varieties are tropical cacti and, unlike desert cacti, cannot tolerate dry soil. Keep the soil evenly moist for best results and water only when the top inch of the soil has dried out.


Purple and white gloxinias

This holiday plant with its large bell-shaped blooms and gigantic fuzzy leaves is a show-stopper. Unfortunately, many people toss these holiday plants the moment they’ve stopped blooming. With proper care, however, gloxinias can become great houseplants, while continuing to bloom all winter.

Like orchids and cyclamens, gloxinias will start to wilt if they don’t like their environment. Unlike cyclamens, however, gloxinias prefer warmer temperatures and they thrive in partial sunlight. Ensure your gift has evenly moist soil and is placed in an area with high humidity (supplement humidity with an humidifier or tray with pebbles and water.) It’s important to keep the water off of the foliage when watering to avoid brown spot.

Gloxinias require a period of rest in order to bloom again. Once the flowers fade, your gift stands a chance of reblooming if you reduce watering by half and resume regular watering only when new growth begins to appear.


Amaryllis just beginning to bloom

Who doesn’t love amaryllis with their gigantic trumpet-shaped flowers and ultra long stalks? Deep red is most common, but they also come in pink, salmon and white. Amaryllis naturally flower in winter, making them the perfect holiday plant. I’ve been gifted amaryllis in several forms’ as a bulb, pre-planted in a beautiful container and as a full-grown plant, nearly in bloom.

If you’ve received a gift of a bulb, place your amaryllis in a warm, sunny spot and water it thoroughly, making sure to drain the pot well after watering. After growth starts to appear, feed the bulb once a week with a bloom booster fertilizer. Once the flower buds start to develop, move the plant away from direct sunlight to prolong the life of the emerging blooms.

After the blooms have faded, remove the spent flowers so the plant doesn’t go to seed, but preserve the stalk. Wait until the stalk yellows before removing in order to furnish food for the bulb (and subsequent blooms.) Move the plant back to an area where it can receive plenty of bright sunlight. Click here for detailed information from the University of Minnesota on how to coach it to rebloom indoors the following winter.


Poinsettias in the nursery

Like anthuriums, poinsettias’ flowers are actually bracts. The flower is the tiny cluster of yellow orbs in the center. While many people choose to toss this holiday plant after the festivities, I like to hang on to mine for a little bit longer.

Poinsettias fare better with lots of good air circulation. Remember to remove the foil wrapper (to prevent drowning your plant when you water it) and place the plastic pot on a saucer so water drains properly. Like all other holiday plants, poinsettias prefer a regular watering schedule, allowing the soil to dry out between waterings. Give your poinsettia plenty of sunlight to keep its colors looking bright and avoid fertilizer, which will hasten the decline of the colored bracts.

For more information on some of the new exciting poinsettia hybrids that offer more than the traditional red or pink, click here for photos from the U.S. Botanic Garden’s holiday display.

What Dirty Old Birds Can Teach Us About Air Pollution

Bird specimens at the Field Museum of Chicago

It couldn’t help but attract my attention; a neat row of old, preserved birds, their soft, feathery chests face-up: some were dark with soot, others by comparison, were clean. All came from an industrial area in the United States called the Rust Belt. That is key to the story.

The birds are part of a collection at The Field Museum in Chicago that dates back to the early 1900s. For a number of years, researchers and museum visitors had been noticing that some of the bird specimens looked clean while others appeared dirty. So recently, scientists from the museum and the University of Chicago decided to take a sharper look and see if they could come up with an answer.

What birds can tell us about black carbon pollution

The above red-headed woodpeckers and the yellow-throated larks (below) formed part of a study just released from the National Academy of Sciences that provided a surprising answer to the question. To decipher why some of the birds were more dirty than others, researchers studied over 1,300 museum specimens. What they discovered was that the birds’ degree of cleanliness corresponded directly with levels of air-borne pollution during their lifetimes, specifically black carbon.

Horned lark specimens

The birds’ chest feathers turned out to be a perfect tool for tracing the amount of black carbon that was present in the air over time. Why? Because the soot clung to their feathers and accumulated year after year.

“These birds were acting as air filters moving through the environment” said Shane DuBay, a graduate student at The Field Museum and the University of Chicago and one of the authors of the study. “The soot on these birds’ feathers allowed us to trace the amount of black carbon in the air over time, and we found that the air at the turn of the century was even more polluted than scientists previously thought,” he said.

Brown coal, which is used to power electricity, has a carbon content of 70-80 percent

Coal and black carbon

According to the Center for Climate and Energy Solutions, black carbon (BC), a long-known source of health and environmental concerns, has also recently emerged as a major contributor to global climate change, second only to C02. Until the mid-1950s, however, direct environmental samples were hard to come by.

Red-headed woodpecker

The birds, however, had lived in the part of the U.S. known as the manufacturing belt, a highly industrialized region historically reliant on coal. By analyzing the different specimens and plotting them on a time line, the researchers were able to go back in time and develop a correlation between the birds’ sootiness and a century’s worth of industrial and environmental approaches to combatting black carbon pollution. This gave them key insights into just how effective these policy approaches were.

For instance, during the depression, when there was a sharp drop in coal production, there was a drop in soot on the birds, too. Birds got dirtier again during World War II when wartime manufacturing drove up coal use. Birds got cleaner when people in the Rust belt started switching to gas to heat their homes in lieu of coal.

What is surprising to those of us who are worried about air pollution, is that the more recent specimens’ feathers are actually cleaner than those of the turn of the century (when we first started collecting birds, apparently).

Today’s horned larks are a lot cleaner

Still, the birds could be picking up less detectable amount of pollutants from other sources. All interesting things to ponder as the United States debates the future of coal, which currently provides 30 percent of the country’s energy. Meanwhile, the dirty birds provide silent testament to the legacies of our sooty history.


Spring Bulbs: Still Time To Plant Some Of These 10 Great Varieties

Spring bulbs in a formal garden setting

Yesterday I directed the planting of two thousand spring bulbs. We placed them individually in patterns and our very capable team dug them one-by-one into the ground. When they were finished, we dressed the bulbs with a thick layer of mulch and all stepped back to admire our handiwork. The garden felt as if it were bursting with energy with so much spring promise nestled snuggly underground.

In Maryland, it’s almost too late to plant bulbs; but according to Patrick Gravel, a local plant expert, as long as you can get the shovel in the ground, there’s still time. Of course, by now most of the on-line bulb suppliers are pretty much sold-out. But, a quick run to the local nursery could still yield some interesting results.

Gravel came up from Richmond last week to speak to my garden club on how to garden with bulbs. Below is a detailed breakdown of the great bulb varieties he profiled. If you’re up for the task, many of them are still out there just waiting to be planted.


For me, the challenge of planting spring bulbs (like now) is the colder weather. Just when I’m turning my attention indoors, the bulbs need to go in the ground. This sometimes requires the ability to dig lots of holes outdoors when the temperature is hovering around 40°F (like yesterday.) Still, if you can visualize what the spring will look like, the reward is directly proportional to the amount of energy you’re willing to expend.

Carpet of blue muscari and other spring bulbs (Keukenhof, Holland)


Allium – Also known as ornamental onions, these drought-tolerant and easy-to-grow late spring/early summer bloomers come in a wide variety of colors, sizes, shapes and forms. Tall varieties include the giant purple-flowering GlobemasterGladiator, and Purple Sensation, the reddish-flowered, oval-shaped Drumstick, the light purple, spidery-flowered Shubertii (Persian Onion), and the rosy purple-flowered Millenium, which is the 2018 Perennial of the Year.

Giant purple allium

Anemone – small in stature with good primary coloring, anemones are great naturalizers. They bloom early to mid April, topping out at 4” at most. The low-growing, daisy-like Anemone blanda, or Grecian Windflower, makes an ideal companion for tulips and daffodils. “A nice early groundcover if you’re waiting for something else to emerge,” said Gravel.

Anemone blanda

Crocus – Gravel thinks of crocuses as ‘little surprises’. You need to plant them early, though, since they’re among the earliest spring bloomers. (Plant most varieties in mid October-mid November.) Look for Giant Dutch crocus, and the even earlier-blooming Snow crocus. Autumn Crocus, which is not a true crocus, but a colchicum, bears purple-pink or white flowers in September or October and must be planted in August.

Dutch crocus

Fritillaria – A member of the lily family, these spring-blooming bulbs have unusual, bell-shaped flowers. Crown Imperial grows to 3′ tall and has lily-like foliage (with a grassy head tuft), Snake’s Head grow to around 1′ tall and have checkered petals and the purple to black-flowered Black Persian grows to around 3′ tall.

Snake’s Head fritillaria

Hyacinth – Gravel advises wearing gloves when handling hyacinths, because the oil from the bulb is an irritant. Highly fragrant, they naturalize quickly and are easy to force inside (more on that below.) Problems are they tend to be floppy. Gravel recommends planting them deeper to give them more structure or planting them with low caging to keep the blooms upright. Click here for Holland Bulb Farms’ selection.


Hyacinthoides – Not the same as hyacinths, these woodland flowers have nodding, bell-shaped flowers in bluish-lavender flowers. Commonly known as Spanish and English bluebells.

Spanish bluebells

Muscari – Commonly known as Grape Hyacinth, these high-fragrant, tiny spring bloomers form rivers of brilliant blue to purple color under taller spring flowers like daffodils and tulips.

Muscari, commonly known as Grape Hyacinth

Narcissus – Named for the Greek hunter who fell in love with his own beauty, narcissus come in a wide variety of sizes, shapes and forms. Some of the most common are: the traditional, single-flowered Trumpet, the slightly smaller Large Cup, the flat-flowered Small Cup with distinctly colorful edges, the clustered/layered cupped Double, the diminutive Jonquil, Tazetta (also known as Paperwhites), and Poeticus with its small cup edged with red.

Double daffodils

Snowdrops – “A very simple bulb, you can’t go wrong with these February-March bloomers and they naturalize easily,” said Gravel. Choose from Galanthus elsewii, Galanthus nivalis, and the taller Giant snowdrops, Leucojum aestivum.

“There are many, many different varieties of snowdrops out there with tiny, tiny differences, said Gravel. “It’s a really nerdy plant.”


Tulips – According to, there are over 3,000 registered varieties of this popular spring bloomer. Some of the most common are Darwin, Triumph, Double, Fringed, Parrot, Fosteriana and Greigii. The diminutive species tulips like Bakeri are long-lived and great for the front of the border. Gravel recommends using chicken wire to protect the bulbs from digging animals.

Fringed tulips


This is much easier than you think. Gravel says the easiest bulbs to force are amaryllis and paperwhites. ‘All they really need is water,” he said. The rest of the spring-blooming bulbs require a 6- to 8-week cooling period that mimics their outdoor period of dormancy.

Plant the bulbs in well drained potting soil and keep in your refrigerator at a temperature ranging around 45 degrees F for 6 to 8 weeks. Keep the soil moist, but not soggy. After the cooling period, bring the bulbs out, place in a sunny location and enjoy.

Amaryllis bulb just beginning to sprout indoors

Patrick Gravel works at Sneed’s Nursery in Richmond, Virginia and lectures frequently on plants and plant life. He can be reached at

Five Reasons Your Trees Are Failing: A Bartlett Tree Expert Speaks Out

Trees are generally admired for their surface beauty, but their health and vigor springs from what’s underground. That’s according to Dr. Kelby Fite, Director of Research for Bartlett Tree Research Lab in Charlotte, North Carolina, who spoke to Maryland’s master gardeners last week. His lecture entitled ‘Managing the Landscape Below Ground’ provided a wealth of information about how to improve the life of the trees in our landscape. According to Fite, it all starts with the soil.

“We are all guilty of fouling up the soil,” he said. “But, it’s far easier to preserve soils than to remediate after they’re damaged.”

Before reaching for the fertilizer, Fite advises digging a little deeper into the source of the problem. Following are five common reasons that trees fail and what to do about them.

Soil Compaction

When it comes to tree health, nothing hurts a tree more than compacted soil. Often brought on by construction, soil compaction impacts trees at their roots, depriving them of essential water, oxygen and nutrients. It also makes it harder for a tree to anchor itself in the soil.

Compacted soil makes tree anchorage difficult 

Soil compaction occurs when soil particles are compressed by external factors like mechanical or human traffic, resulting in reduced pore volume (meaning there is less space for air and water.) Heavily compacted soils have a reduced rate of water infiltration and drainage and are often hydrophobic (meaning the water runs off). For a tree, this leads to poor growth, higher water needs and increased susceptibility to pests and disease.

Fertile, aerated soil

Compacted clay soil

Think of soil like a sponge, with large and small particles.

“What happens when we squeeze a sponge?” Fite asked. “We are increasing the amount of solid matter.”

It makes sense. Tree roots are extensive and with the exception of the taproot, located for the most part just 8 to 10 inches below the soil. They need space to grow. With compaction, however, many trees will never develop a taproot, instead establishing a network of weakened lateral roots that are unable to keep the tree vertical. And at the soil surface, the fine feeder roots (which under ideal conditions can extend 4 to 7 times the drip line of the tree) are compromised, too. This reduces a tree’s ability to absorb water, oxygen and nutrients and ultimately leads to its decline.

SOLUTION: Build away from a tree’s drip line and keep mowers and other machinery off the soil. For existing trees under stress, add a mulch circle. (More on that below.)

Raking up leaves deprives trees of important nutrients

This is a tough one. I’m not sure I’m ready to shred leaves and leave them all over my lawn. But think of it, we spend time and money to rake up one of our plants’ most important sources of nutrients, push them to the curb, then go to the store and buy them back again as mulch or soil additives.

“It’s not a great business model,” said Fite.

According to Fite, we are removing one pound of nitrogen per 1000 feet just by removing the leaves from our properties. This is a big loss for trees as well as other plants. And this doesn’t even take in to account the fossil fuels burned to operate leaf vacuums.

Our soils are low in organic matter because we are not allowing leaves to decompose like they do in the forest. When left alone, leaves return nitrogen and other organic matter to the soil. They also protect the soil surface, adding to its water holding capacity. And as they break down, they provide porosity and aeration, allowing more water to infiltrate the soil.

Shredded leaf mulch

SOLUTION: Shred your leaves with a mower and make leaf compost or leaf mold mulch (not the same thing.) For some great info on how to do both, click here for’s excellent article Rake leaves and make compost, mulch. 

Modified soils have higher pH which is bad for trees

In a perfect soil world, soils have a slightly acidic to neutral pH (a pH of 5.5 to 6.5). Urban and suburban soils, however, often contain debris left behind from construction. This generally results in a higher soil pH due to leeching from masonry walls and foundations.

Leeching from masonry leads to soils with higher pH

Trees growing in these locations may show signs of nutrient deficiency (like yellowing of leaves) and may be slower to establish. And irrigation water typically has higher pH, too. This means it gradually increases the pH of adjacent soils over time. This can result in a dramatic difference between the nutrient ability of your native soil and that affected by construction materials.

SOLUTION:  Do a soil test to determine the pH and get the turf out from under your trees. Lawn thrives on alkaline soil (that’s why we add lime.) But trees like a lower pH. All developed soils tend to have a higher pH and modified temperature, putting more heat stress on plants.

A soil test report from University of Delaware (my go-to destination for soil reports)

Lack of mulch

Mulch improves soil structure while providing protection to a tree’s roots. It supplies organic matter to the soil that reduces compaction. And it moderates soil temperatures, conserves moisture and eliminates competition from grass. Yet, many landscape trees are planted out in the lawn with no protection.

Fite recommends mulching out to the drip line of a tree if you can. It will help prevent ‘mower blight (or your mower banging into the trees) and also protect against stripping from string trimmers. Mowers, by the way, also contribute to soil compaction, especially when they’re operated in wet conditions.

Mowers contribute to soil compaction and can damage a tree

SOLUTION: Create a mulch circle around your trees. It will help protect them from mower damage and as the mulch decomposes, it will aerate the soil and provide nutrients.

Fertilizing when it won’t make any difference

According to Fite, fertilizer doesn’t fix everything. Pull a soil sample from around your tree first to determine whether or not to fertilize. Most soil labs will run diagnostics on your sample and send you back a prescription for what to add to your soil to improve its composition.

Before fertilizing, ask yourself what is the objective? If construction has occurred and interrupted a tree’s root zone, no amount of fertilizer is going to fix the problem.

And remember, although native soil usually contains lots of organic matter, during construction this layer is often buried under layers of sand or debris. Or sometimes, it’s stripped off entirely. No amount of fertilizer is going to bring life back to this kind of soil.

SOLUTION: Do a soil test to find out what your soil is made of before reaching for the fertilizer. Fix the soil first, then use fertilizer to adjust accordingly.


Fite offered a couple additional suggestions for how to get your trees back in shape (assuming you haven’t destroyed most of the root system by building too close):

Invigorate the roots

Many times the best thing you can do for your trees is to invigorate their roots. Bartlett uses an air spade, a tool that uses an air compressor to generate a high velocity jet of air to dislodge the soil. The rush of air breaks up and ‘tills’ the soil without removing it to a depth of about 8’ (the depth of the feeder roots). This method of improving the soil leaves root systems intact.

Air spade in use at Western Illinois University

The air spade was originally developed by the military to clear land mines. Nowadays, it is used by landscapers and arborists to invigorate roots. After the soil is excavated, add soil, compost and mulch to settle the soil back down. Then water the tree.

Look into Biochar

Mulch breaks down because the microbes eat it for carbon, resulting in it having to be replaced every year. Charcoal, on the other hand, is stable, meaning it lasts for centuries. Biochar is a fine-grained, highly porous charcoal that is added to soil to help it retain water and nutrients. It acts like a dry sponge, but on its own contains no nutrients, so blend with compost for best results.

Biochar acts as a dry sponge, but contains no nutrients

“Put the two together and magic happens,” said Fite.

Buyer beware, though, biochar is not regulated, so buy from a reputable source and read the label carefully.

Kelby Fite, Ph.D. is a VP and Director at Bartlett Tree Research Lab.

Tree ID: How To Be Your Own Best Detective

Giant tulip poplar in Orange, Virginia

I remember the first time I realized the value of knowing a tree’s name. I was walking with a friend along the C & O canal in Great Falls, Maryland when she began identifying the trees around us. As we passed, she stopped to observe different species, remarking on their personal characteristics and quality of growth. Suddenly for me, the woods took on an entirely new dimension.

Most of us feel more comfortable in public when we know people’s names and a little bit about them. I learned that day that the same goes for trees. Acknowledging each by name allowed us to communicate with and about them, opening a door into a world that had until that moment been only green.

Elm tree

Knowing a tree requires undivided attention

I’ve made great strides learning names of trees over the past decade. Still, I remain frustrated by the ones I don’t know. Just when I think I’ve nailed it, someone will present me with an oddball leaf I can’t readily identify. And, as a garden designer, most clients expect me to be not only an expert on shrubs and perennials, but trees as well.

So recently, I was happy to learn that the Audubon Naturalist Society (ANS) was offering a full-day lecture on native tree identification in Chevy Chase, Maryland. The lecture was held in a beautiful old brick home that serves as their location. Girded on all sides by dense woodland, the property features some of the most magnificent mature trees in Maryland.

Audubon Naturalist Society headquarters in Chevy Chase, Maryland

Our instructor, senior naturalist Stephanie Mason began our lecture with this quote from Edgar Allen Poe:

To observe attentively is to remember distinctively.

OK, Poe was speaking about investigating murders, not trees, but Mason feels the quote applies. To be a good tree identifier, you need to first become a good observer. She cautioned that even the experts don’t expect to identify everything correctly.

“It’s a big plant word out there,” Mason said. “If you know how to use a field guide, you’re already on your way. You have to go out and observe again and again. And then go out and observe again.”

And with that, we were off to the races.

Dried seedpods (samaras) of a maple

Five easy steps to identifying trees

There are many characteristics that can be used to identify trees, including overall size and shape of the tree, size, shape and arrangement of leaves, buds, bark , fruit and flowers. Most people use a combination of the above. Still, when attached to the tree, leaves are the most common identifying feature. We started by snapping off a twig with some leaves on it and asking ourselves these questions:

Step 1. Are the leaves single or compound?

A single leaf is attached to the twig on its own, while a compound leaf consists of a number of leaflets that together, comprise one leaf.

Step 2. How are the leaves arranged on the tree?

One important tool to identifying trees is to determine the placement of the leaves on the tree. Are the leaves growing opposite or alternate to each other on the twig?  To aid in the task, Mason shared with us a useful mnemonic. (This is used for remembering which trees have opposite leaves in our area.)

MAD HORSE    Or, Maples, Ashes, Dogwoods and Horse chestnut.

Step 3. What do the leaf margins look like?

Next is to zero in on the leaf itself. Are the margins smooth, wavy, toothed or lobed? (In some cases, you may need a magnifying glass to better observe the leaf margins.)

Step 4. What is the veining like on the leaf?

Turn over the leaf and look at the veining. There are two types of veining that can occur. Palmate leaves have veins that spread outwards from a central point, just like fingers on a hand. A maple leaf is palmately veined.

Pinnate leaves have veins that extend outward from a central spine, like a feather An oak leaf is pinnately veined.


Step 5. What do the terminal buds look like on the twigs?

This simple step often helps ID the tree the fastest. For instance, the terminal buds of flowering dogwood trees have a distinctive onion shape.

Terminal bud of Cornus florida, Flowering Dogwood/Stephen J. Baskauf

The Dichotomous Key

Dichotomous keys are useful tools that help people identify things in the natural world. The keys consist of a series of choices, A or B, that lead the user to the correct name of the species. Our tool for the day was ‘Common Native Trees of Virginia’, but there are many other dichotomous keys for identifying items from all over the world. Tree ID experts use them all the time.

The keys always start with the same choice, Choice Number One. Once you have determined which answer best describes your specimen, you go to the number where the choice directs you. You follow the numbers in this way, continuing to read and select answers until you arrive at the name of the tree. It’s a lot like a treasure hunt and an invaluable resource for deciphering plant life in your area.

Interested in learning more? There are dichotomous keys for just about everything. Look for one that applies to trees in your area and get started! (Click the link above for a list of what’s available on Amazon.) I guarantee it will open up a whole new world.



Trending In Health: Shinrin-Yoku (Forest Bathing)

Most of us are well aware that a walk in the woods is a breath of fresh air; especially if you’re stressed out from big city life or the artificial glow of computer screens. But now in a growing trend, people are heading to the woods to experience nature in a completely different way. It’s called forest bathing.

In Japan where the idea originated, forest bathing is known as Shinrin-yoku and it’s been shown to reduce stress, increase resistance to disease and promote well-being. No, people aren’t taking an actual bath in the woods, but they are engaging in something equally immersive. They are walking in the woods for the sole purpose of improving their health, following designated therapeutic ‘routes’, while tuning their minds into the colors, scents, sounds and feel of the forest.

Forest bathing has been a part of Japanese culture for years. And following a decade of official practice, it is now attracting attention worldwide. Currently, Shinrin-yoku (roughly translated as ‘taking in the atmosphere of the forest’) is gaining in popularity not only in Asia but in Europe, Scandinavia and America as well.

Why the trend? Because research shows there are measurable benefits to regular exposure to forest environments. In fact, just a few minutes spent walking in parks or green spaces can boost levels of energy and drive down everyday feelings of stress and anxiety.

Bamboo forest in Kyoto, Japan

Back in 1982, the Japanese were already aware of the harmful effects stress can have on the body. With job-related pressures on the rise, the Forest Agency of Japan began promoting forest bathing trips as part of a healthy lifestyle. Although forest recreation was a long-established form of relaxation, this was the first time the practice had been prescribed specifically to manage stress.

And, while no one could pinpoint exactly how it happened, more and more people were starting to report a positive therapeutic effect.

The science behind forest bathing

Researchers already knew that forest environments could have a profound effect on humans via their senses. As pleasant sensory experiences traveled to the brain, they interacted in positive ways with the part of the brain that controlled emotions and physiology. Scientists hypothesized that there might be a quantifiable link between forest bathing and a subsequent improvement in these functions.

The soothing sounds of a forest stream 

So in 2005, in an effort to better understand the longterm effects of forest bathing on people’s health, the Forest Agency instituted the Therapeutic Effects of Forests Plan. The goal was to discover what, if any, physiological benefits resulted from sending people into nature, specifically, forests, as a therapeutic practice. The scientific investigation, which wrapped up in 2014, uncovered some surprising information.

The study

To better understand the effects of an individual’s exposure to a forest or its components (such as streams, blossoms or wood), the researchers conducted experiments using 456 subjects and 38 forests over a period of four years. Subjects were randomly divided into two groups and were given identical single rooms as lodgings and identical meals and water to control for background environmental conditions.

On the first day of each experiment, half of the subjects took a walk in a forest or wooded area for a few hours, while the other half spent an equal time walking in the city. On the second day, the groups switched places. Scientists measured their subjects’ salivary cortisol, blood pressure, pulse rate and heart rate variability before breakfast and both before and after walking to see if there were any measurable effects.

Phytoncides emitted by trees can improve human health, too

The studies revealed some interesting dynamics. Compared to the city walkers, those individuals who spent time in the woods had significantly lower concentrations of cortisol, as well as lower pulse and blood pressure rates. Their sympathetic nerve activity (which activates the fight or light responses) was also reduced. Most significantly, exposure to phytoncides (aromatic chemicals or oils emitted by plants and trees to protect themselves from insects and disease) had a lasting impact on peoples’ immune systems, boosting their natural killer cells and anticancer proteins by an astonishing 40 percent.

As a result of this study, forest bathing has now become an integral part of preventative medicine in Japan; so widespread that a quarter of the population is reported to be practicing it on over 55 official Forest Therapy Trails. Some Japanese companies are even starting to include forest therapy in their healthcare benefits, offering wellness check-ups in the woods as a part of a new ‘nature prescription.’

Forest and humans : We’re in this together

Humans have been getting ‘in touch’ with nature for ages and almost no one would dispute the natural world’s beneficiary effect. While this is the first scientific evidence of forests’ positive impact on humans, some people point to the human evolutionary process itself as proof that nature and humans have always had a deep-seated connection. They note that until recently, most of the 5 million years of our existence has been lived in the natural environment.

Consider this: If human physiological functions were designed for living in nature, then life in modern, artificial environments must by definition be innately stressful. Immersing the body in nature puts it back where it was meant to be.

Nuuksio National Park, Finland

The Master Samurai Spain, who has led studies on Shinrin-yoku in Andalusian forests for the past 10 years, agrees. He believes the root of the problem is that human beings are not adapted to live in hostile environments such as cities. As a result, those suffering from modern-day stresses and anxiety have weakened immune systems that cause them to become sick. Forest bathing allows the body to absorb beneficial compounds associated with millions of years of plant growth. This helps it fortify its defenses.

Trees aren’t just about good looks

Trees aren’t just beautiful, they provide shade that cools our homes and bodies. Like all plants, they perform photosynthesis, converting sunlight into food for insects, wildlife and people. They also act as nature’s water filters, drawing on the dense communities of microbes surrounding their roots to clean water in exchange for nutrients. And their leaves filter air pollution on a grand scale, too.

Trees provide wood for our fires and building materials for our furniture and homes. They stabilize our planet’s soil. And their soothing sounds, pungent smells and visual stimuli have calmed our anxious minds for centuries. Now comes the first scientific proof of what we’ve innately known all along. Forest bathing may be the cure for what ails us.

Intrigued by the idea? is a great resource for places offering the practice.


Dreamy Dahlias: 10 Ways To Identify Your Perfect Type

A cactus dahlia blooming in my garden

Fall may be poking a tentative finger into my garden, but my dahlias still think it’s summer. Every morning I wake up to a multitude of new blooms. And, no matter how many I harvest, the next day there are still more waiting to be cut. To me, October means breakfast with an armload of fresh flowers, their brilliant, flat-tipped petals still wet with the morning dew.

My first memories of dahlias date back to the 1960s when I was a kid growing up in northern Delaware. This was a time when suburbs were still interspersed with working farms in an eclectic mix of cow pastures and neatly manicured lawns. One such farm was located at the crossroads of two suburban streets, Silverside and Faulk. In September, the portion of the property adjoining the busy corner was transformed from grassland into a field of dahlias.

And these weren’t your ordinary dahlias, mind you, many were the gigantic, dinner plate size; the kind that drives a kid mad with desire to jump out of the car just to be among them. Standing as tall as adults, they would gently sway in the breeze, tilting their giant heads in salute as we slowly motored by.

I’d crane my neck out the window and watch them until they gradually disappeared, dissolving as one into a sea of rippling colors.

Thus began my love affair with dahlias.


So many dahlias, so little time

Dahlias are tuberous, herbaceous perennials that are native to the tropics. They are members of the Asteraceae family. Classified as tender perennials, they may be annual or perennial, depending on what the climate is like where you live.

The flamboyant flowers are perhaps best known for their tall, celery-like stems and gigantic flowers, but they come in all kinds of sizes. These range from the very tall (around 7 feet) to just under 12 inches. There are thousands of varieties.

Dahlia flowers also range widely in size, from a diameter of around one foot to just under 2 inches. And within the different size groups, there are different flower types, each with their own classifications. These include dahlias featuring single, double and semi-double petals, those that have unusual shapes like spherical or cactus, and varieties that resemble other flowers like anemones, peonies, orchids and waterlilies.

Waterlily dahlia ‘Pam Howden’

Last but not least are the dazzling colors – a seemingly infinite variety of gorgeous pinks, reds, scarlets, oranges, purples and yellows, as well as creamy and brilliant whites. Many flower petals often come with strips or tips of another color.

So, with so many options to choose from, how to decide? One way is to get acquainted with the most commonly used classifications. These help define each dahlia’s unique shape and structure and can aid in their selection.


Single-flowered dahlias feature a single row of flat or slightly cupped ray petals surrounding a central disc.

Single-flowered dahlia

Semi-double dahlias have two or more rows of petals surrounding a central disc.

Semi-double dahlias

Mignon dahlias are similar to single dahlias except their petal florets are rounded and their disc flowers have no more than two rows.

Mignon dahlia with burgundy/black foliage

Anemone dahlias have an inner disc made up of elongated, tubular shaped florets and an outer ring of one or more rows of flat ray petals.

Anemone dahlia ‘Polka’

Orchid dahlias are open centered flowers with just one row of ray florets surrounding a disc. The petals are often overlapping and curled for most of their length.

Orchid dahlia

Collarette dahlias have one row of flat petals surrounding a disc as well as an inner wreath of shorter petals called the ‘collar’.

Collarette dahlia ‘Mary Eveline’ plum red petals with white ‘collar’

Ball and Pompon dahlias are ball-shaped and feature double flowers with rounded or blunt tipped florets. Ball dahlias have round, cupped petals that are spirally arranged in a honeycomb shape. The flower may be slightly flattened. Pompon dahlias are slightly smaller. They are known for their perfectly round flower head.

Orange ball dahlias – notice the slightly flattened shape

The perfectly round pompon dahlia ‘Franz Kafka’

Decorative dahlias are double dahlias that feature flat, oval petals with tips on the end. Formal varieties have regular, evenly placed petals, while informal varieties tend to be arranged in a more haphazard way. Both varieties grow to over 40 inches.

Decorative dahlia ‘Lisa Dark Pink’

Cactus and semi-cactus dahlias. Both have narrow pointed petals that roll back on themselves, giving them a spiky look. Cactus types are rolled for their full length, while semi cactus types include a mix of flat and rolled petals. Both are considered double flowers and reach an average height of around 40 inches.

Orange cactus dahlia

Semi-cactus dahlia ‘Aloha’

There are so many other varieties, including peony, waterlily and stellar, not to mention the celebrated ‘Dinner Plate’ which falls under numerous categories. The Miscellaneous Dahlias category alone includes hundreds of varieties.

Ready to add dahlias to your garden? (or in my case add more). Here’s how.

When to plant

Dahlias are sold as tubers. I like to plant them just around the time my tulips have faded, in well drained soil in full sun. You can also pot them up a couple weeks beforehand to give them an early start.

Considered hardy outdoors in USDA zones 8 to 10, dahlias are considered tender in my neck of the woods (Zone 6.) Once they’re done flowering in the fall (or right after the first frost), I dig them up, label them and store them in a dry spot in the basement.

Want to learn more about dahlias? Visit Longwood Gardens’ annual dahlia show, held each year in Kennett Square, Pennsylvania. Looking for a great place to buy tubers? Check out the beauties at Eden Brothers, one of my favorite online sources.

Dahlias were named for the 18th century Swedish botanist Anders Dahl.


Bees, Wasps and Hornets: Here’s How To Tell The Difference

Four common bees and wasps

What is the difference between bees, wasps and hornets? This is a question I tend to ask myself, especially when surrounded by swarms of hungry yellow jackets while dining outside. I, for one, know from experience that fuzzy honeybees can make excellent garden companions. But, what’s up with their skinny yellow and black striped brethren? Do they have any value? They seem interested only in stinging me. Continue reading

Daylilies Giving You Trouble? Here’s How To Divide Them

Hemerocallis fulva, commonly known as Tiger Daylily

We parents know that when our children aren’t getting along it usually helps to divide them. The same goes for many perennials that stop behaving as mature specimens in the garden. Daylilies are one common plant that benefits from a good shaking up from time to time when things start to get out of control.

Warning signs

You may have noticed that your daylilies aren’t blooming as prolifically as they used to. Or that they’re crowding out or overshadowing other plants in the garden. Recently I lifted up an overgrown clump of ‘Happy Returns’ (pictured below) to find a few forgotten Heuchera ‘Obsidian’ barely surviving.

If this sounds familiar, now is the time to start dividing!

Tips for dividing

It’s pretty hard to kill daylilies (I’ve left clumps out, unplanted, for an entire winter and they still flowered come summer.) However, to play by the rules, most experts advise dividing them right after they flower, or in late summer or early fall.

Depending on your soil type, daylilies can be a bear to dig out. I prefer using a long, narrow shovel with a platform step for my foot. This seems to be the right length for getting under the daylily while providing me with a little extra leverage.

Step 1

Start by inserting the shovel into the soil about 6 inches away from the roots. Dig around in a circle, gently prying up the plants as you go. Once the plants are loosened, slide the shovel horizontally underneath the clump and cut it from the ground.

TIP:  Most times I dig the whole clump up and immediately begin dividing. However, you can save a little time by leaving a small sized clump in the ground.

Step 2

Once you’ve removed the clump, you have two choices. You can simply cut it into smaller groups, leaving the soil on. Just dig new holes and replant. (Don’t worry if you cut through a few of the roots. The plants will do fine.)

Or, you can remove the dirt from around the roots and pry the plants apart. I prefer this latter way because it gives me an opportunity to tease out the roots and replant my divisions in fresh soil.

If the clump is a large one (which it probably is if you’re dividing it), then 4 to 5 fans (green sections) is a good number. This will ensure you get blooms the next year.

But, there’s no reason you can’t break the clump down to single fans if you’re looking to fill a big area. You may have to wait a year to see new flowers, though.

Step 3

Not really a step, but very important: No matter how many divisions you choose, always leave a fan attached to the roots. Without it, the daylily won’t grow.

Step 4

Finally, replant your divisions 12′ to 18′ apart (remember, daylilies grow fast), adding compost or LeafGro to the soil. Build a small mound under your transplant and fan the daylily roots out into the soil. Cut the foliage back to around 4 to 6 inches, water generously and look forward to next summer’s abundant new blooms!