When I was a teen, a French girl came to live with us for the summer. She caused quite a stir in our button-down town with her skinny jeans, lace-up wedge espadrilles and oversized red glasses. That being said, what I remember most was her preference for a men’s cologne named Pino Sylvestre. Wherever she went, an intoxicating ‘green’ fragrance trailed in her wake. Continue reading
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. Continue reading
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. Continue reading
Yesterday I supervised the planting of 5,000 spring-flowering bulbs. We laid them out in patterns and dug them one-by-one into the earth. When we were finished, we dressed the bulbs with mulch and all stepped back to admire our handiwork. You could almost sense the pulse of spring making its way up from underground. Continue reading
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, NC. Recently, he spoke to Maryland’s master gardeners on the reasons why trees fail.
Fite’s 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 why trees fail and what to do about them.
When it comes to tree health, nothing hurts a tree more than compacted soil. Often caused by construction, soil compaction strikes trees at their roots, depriving them of essential water, oxygen and other nutrients. It also makes it harder for a tree to anchor itself.
Compacted soil makes tree anchorage difficult
Compaction occurs when soil particles are compressed by external factors such as mechanical or human traffic, resulting in reduced pore volume. Since there is less space for air and water, these types of soils have reduced rates of water infiltration and drainage and are often hydrophobic (meaning the water runs off).
In the case of a tree, this leads to poor growth, higher water needs and increased susceptibility to pests and diseases. It is also one of the primary reasons why trees fail.
Fertile, aerated soil
Compacted clay soil
Think of soil as a sponge, with large and small particles.
“What happens when we squeeze a sponge?” Fite asked. “We are increasing the amount of solid matter.”
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.
Meanwhile at the soil surface, the tree’s fine feeder roots (which under ideal conditions can extend 4 to 7 times the drip line of the tree) are compromised, too. This reduces its ability to absorb water, oxygen and nutrients.
SOLUTION: Build away from a tree’s drip line and keep mowers and other machinery off of the soil. For existing trees under stress, add a mulch circle. (More on that below.)
This is a tough one. I’m not sure I’m ready to shred my leaves and scatter them all over the lawn. But think about it. We spend time and money to rake up and dispose of one of our plants’ most important source of nutrients. Then we go to the store and buy it 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 don’t allow 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 earth.
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 the spruce.com’s excellent article Rake Leaves and Make Compost Mulch.
In a perfect 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. Moreover, irrigation water frequently has a higher pH, too.
Leeching from masonry leads to soils with higher pH
All of this can lead to a dramatic difference between the nutrient ability of your native soil and that affected by construction and other materials. Since developed soils tend to have a higher pH and modified temperature, they put more heat stress on plants. As a result, trees grown in these locations may show signs of nutrient deficiency (like yellowing of leaves) and take longer to establish. They may even fail.
SOLUTION: Do a soil test to determine the pH and get the turf out from under your trees. Lawns may thrive on alkaline soil (that’s why we add lime), but trees prefer a lower pH.
A soil test report from University of Delaware (my go-to destination for soil reports)
Mulch improves soil structure while providing protection to a tree’s roots. It also 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. This is another reason why trees fail.
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.
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, take a look around the landscape. 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 Tree uses an air spade, a tool that generates 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.
EXPLORE 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. Bartlett Tree recommends blending it 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.
Giant tulip poplar in Orange, Virginia
I remember the first time I recognized the value of knowing a tree’s name. I was hiking with a friend along the C & O canal in Maryland when she began identifying the species around us. As she paused to study the different trees, she remarked on their patterns of growth and unique characteristics. Suddenly, the forest took on a whole new meaning for me. Continue reading
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 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. Continue reading
Minus some advance planning, fall usually spells the end of the garden. But if planted in spring, dahlias will flower non-stop through autumn. Lately, I’ve been waking up to crisp mornings only to discover more and more blooms. Who knew October could bring so many fresh flowers?
For some, dahlias may not be all that big a deal. But for me, the first time I saw the majestic, 10-foot flowers left an indelible memory. It was the 1960s, and I was a kid growing up in Delaware. Smack dab in the middle of suburbia, on the corner of two heavily-traveled streets, there was a small working farm. In the summer it produced fruits and vegetables. But in September, it grew dahlias.
And these weren’t your everyday 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 gently swayed in the breeze, solemnly saluting as we drove by.
Craning my neck out the window, I’d watch until they disappeared, slowly dissolving into a sea of rainbow colors.
And thus began my love affair with these beautiful flowers.
Dahlias are classified as tender perennials, meaning they may be annual or perennial, depending on the climate. They typically start blooming in August with other late-summer flowers. But the best thing about them is that they don’t stop blooming until the first frost, or roughly right around Thanksgiving.
And in spite of their reputation for towering stems and gigantic blooms, the plants come in all shapes and sizes. Dahlia types can range in height from the very tall specimens of my childhood to just under one foot. Planting the tubers is easy. Just dig a hole 6 to 8 inches deep and drop them in with the ‘eyes’ facing up. Three or more tubers per hole usually gives the most colorful effect.
Still, it goes without saying that the most notable feature of all dahlias are the flowers. These can range in diameter from 2 inches to almost one foot. And among these, there are specific dahlia types, each with its own specifications. For example, there are species with single, double and semi-double petals. And there are unusual shapes like spherical or cactus. There are also types that resemble flowers such as anemones, peonies or orchids.
Waterlily dahlia ‘Pam Howden’
Notwithstanding the variety, one thing all dahlia types have in common is their dazzling color. These flowers come in a seemingly infinite array, including all shades of pink, red, scarlet, orange, purple and yellow. Moreover, the flower petals often come painted with strips or tips of another color. (There are also creamy ones as well as many brilliant white species.)
In sum, with so many options to choose from, how do you decide? One way is to familiarize yourself with the most common types. You may be surprised to find that some don’t look like the ‘typical’ dahlia.
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 tubular shaped florets and an outer ring of one or more rows of flat ray petals.
Anemone dahlia ‘Polka’
Orchid dahlias have open centers 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 shaped like balls and feature double flowers with rounded or blunt tipped florets. Pompons are slightly smaller than ball dahlias.
Orange ball dahlias – notice the slightly flattened shape
The perfectly round pompon dahlia ‘Franz Kafka’
Decorative dahlias are doubles 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 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 reach an average height of around 40 inches.
Orange cactus dahlia
Semi-cactus dahlia ‘Aloha’
There are 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? Every year, among the ten top things I want to achieve or change in my garden, I resolve to plant more. Here’s how.
Dahlias are sold as tubers and need to be planted after the ground has warmed up and there’s no danger of frost. I usually plant mine in the late spring just around the time my tulips have faded. Plant the tubers in well drained soil in full sun for best results. You can also pot them up indoors a couple weeks beforehand to give them a head start.
Dahlia tubers need to winter indoors in a cool, but not cold, space
Dahlias are considered tender in my neck of the woods (Zone 6), but hardy outdoors in zones 8 to 10. That means that once they’re done flowering in the fall (or right after the first frost), I must dig them up. I then label them and store them in a dry spot in the basement. Click here for the USDA Plant Hardiness Map to see where you fit.
To see photos of my garden designs, including plant lists, check out my Instagram at carole.herebydesign. I post seasonally from spring through fall.
When kids can’t get along, parents know it’s time to divide them. The same goes for perennials that won’t make room for other plants in the garden. And daylilies are one of the biggest offenders; quickly crowding out other, smaller species with their big, drooping foliage. But don’t despair. Just follow the simple steps below and you’ll have things back under control in a jiffy. Continue reading
My September garden
The end of September can be a tough time for gardens. Leaves lose their deep green luster, stems start to brown and many perennials have simply lost their will to survive. Add to that the fact that the lower the sun gets in the sky, the more dull colors can appear and suddenly, the same flowers that looked so vibrant in summer begin to take on a more muted, less enthusiastic look. Continue reading
