In The Zone: The USDA Plant Hardiness Map Explained

Most of us know not to plant watermelons in the mountains or aspen trees at the beach. But when it comes to the countless plants available at the nursery, things can get murky. That’s when a handy tool called the USDA Plant Hardiness Zone Map can make all the difference. Not only can it tell you what plants will survive where, but it can also ensure a year’s worth of success in the garden. Continue reading

How To Pronounce Botanical Names (Hint: It Doesn’t Matter)

Just the other day, I was working with a bunch of Master Gardeners preparing a garden for the county fair when one of them noticed a bare space. Sure enough, in one of the central beds, a group of plants had recently given up the ghost on a prominent corner. In no time, we all agreed that a lacy evergreen would be the perfect replacement. And that’s when I suggested chamaecyparis. Continue reading

The Real Lives Of Yellow Jackets And How To Get Rid Of Them

Eastern yellow jacket cleaning itself on a leaf

Recently I published a blog post about bees, wasps and hornets. To add interest to the story, I created a graphic featuring 4 common species and asked my readers to identify them. One reader labeled three of them correctly and labeled the fourth one ‘jerk.’ (Actually he used more colorful language, but this is a family blog). That ‘jerk’ was the yellow jacket. Continue reading

How To Deadhead Popular Types Of Flowers

Most flowering plants need lots of sun to keep on blooming. Still, over time, the blooms often start to diminish. That’s where deadheading can make all the difference. Not only does it keep plants looking neat, but it also promotes new growth and re-flowering. And, there’s nothing quite like getting a plant to re-bloom that otherwise looks done for the season. 

WHAT IS DEADHEADING?

Simply put, deadheading is the practice of removing spent (dead) flower heads from a plant. 

Dried poppy seed heads

All plants follow the same life cycle; that is, they grow, produce flowers, set seeds and die. No sooner do the blooms fade, and a plant turns its energy to setting seed. That said, by removing spent blooms, you can delay production of seeds. This in turn redirects energy to flowering. The result is a healthier, more vigorous plant that blooms for a longer period of time.

HOW TO DEADHEAD

Regular deadheading benefits all blooming plants. However, the world of flowers is diverse and many species require their own specific methods. Here are tips on how to deadhead six key types of flowering plants:

Clusters of flowers with leaves on their stems

Purple garden phlox

These types of flowers include tall, leggy plants like phlox, yarrow, daisies. To keep your plant looking neat, remove the spent flowers just before they die back completely.

A good rule of thumb is to reach into the plant and prune the spent flowers back to the first or second set of leaves. This not only helps hide the cut, but it also encourages the plant to bush out as it produces new blooms. I vary the lengths at which I cut to keep the plant shapely.

Flowers with no leaves on their stems

Long-stemmed orange daylily

Flowers like daylilies and hostas have no leaves on their stems. Cut the entire stalk back to the base of the plant once it has finished flowering.

Salvias

Multiple flower spikes of salvia make pruning tedious

Once the initial flush of flower spikes start to brown, salvias look like they’re done for the season. With proper deadheading, however, you can encourage them to keep on blooming.

What may at first glance look like a single flower stalk is actually three flower stalks growing together – a central stem surrounded by two, smaller ones on either side. As soon as the central stalk starts to wither, remove it. This will encourage the side shoots to grow.  Then, once the side shoots lose their color, cut them off too.

Deadheading salvias in this way can encourage the plant to re-bloom at least twice and sometimes three times during the season, especially if you feed it mid way through the summer. Try one of these stunners for great summer color: Salvia patens Cambridge Bluebright red Salvia Jezebel, or the traditional purple/blue favorite Salvia x sylvestris May Night.

Bushy plants with small flowers

Coreopsis verticillata

Bushy perennials like coreopsis can be encouraged to produce a second round of blooms way past their typical flowering time.

However, it can be tedious deadheading so many tiny flowers. Instead, I grab big chunks of spent blooms in one hand and shear them back with a pair of long-blade shears in the other. This not only encourages the plant to re-bloom a week or so later, it keeps thinks looking tidy. Try soft yellow Coreopsis Moonbeam for reliable blooms all summer.

Roses

With roses, the number to know is ‘5’

Most of us know that roses need to be deadheaded to flourish. Remove withered blooms by pruning back to above a five-leaflet leaf, cutting on an angle.

Annuals

Geraniums need consistent deadheading to look their best

All annuals need to be deadheaded regularly to thrive (with the possible exception of begonias, in which case you should prune the leaves.) Popular annuals like geraniums and petunias must be constantly snipped, pinched or cut back to keep flowers looking neat and to encourage blooming. For a more in-depth tutorial on how to prune these annuals, click here for How To Keep Your Potted Plants In Shape All Summer

Self-seeders

Butterfly weed is a prolific self-seeder

Some flowers, like columbine, echinacea and butterfly weed are prolific self-seeders. If you’re looking to produce lots of new baby plants, leave the seed heads on and they’ll quickly spread around your garden.

DEADHEADING WON’T DAMAGE THE PLANT

It’s rare to damage a plant by cutting it. Use common sense while removing spent flowers, taking care to hide your cuts under existing foliage. Remember to sterilize your pruners regularly to prevent spreading disease between plants. You’ll reap the rewards of a new flush of blooms!

Looking for garden design ideas? I post photos of my landscape projects on Instagram

 

Weed ID: Get To Know What You’re Pulling

Warm weather is back and many of our plants are bursting into flower. But as we celebrate, there’s another less attractive family of plants springing into life as well. These are the dark cousins of our ornamentals: the perennial and annual weeds. The bane of all gardeners, they stubbornly return each year, unfazed by our attempts to remove them. Continue reading

Five Reasons Why Trees Fail: A Bartlett Tree Expert Speaks Out

why your trees are failing

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.

COMPACTED SOIL LEAVES NO ROOM TO BREATH

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 leads to tree failure

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

Fertile, aerated soil

compacted clay 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.)

DEPRIVING TREES OF FALLEN LEAVES

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. 

HIGH pH SOILS ARE BAD FOR TREES

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)

TREE ROOTS NEED PROTECTION

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.

FERTILIZING FOR NO REASON 

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.

OTHER THINGS YOU CAN DO TO HELP YOUR TREES

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.

How To Divide Daylilies

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

How To Grow Lavender: A Maryland Expert Weighs In

One of the perks of being a master gardener is all the great lectures you get to attend. And today’s talk following the board meeting was no exception. It happened to coincide with the very moment I was asking myself “What’s going on with my lavender?” Here was professional grower, Sophia Watkins, ready to answer all my questions.

ABOUT SOLEADO LAVENDER FARM

Watkins runs a family-owned, sustainable farm called Soleado Lavender Farm. Located in Dickerson, Maryland, it is the largest of its kind in the state. Watkins grew up on the 286-acre property, 26 acres of which are now dedicated solely to the growing of lavender.

Soleado Lavender Farm

The family prides itself on its long history of organic farming, a practice Watkins’ father adopted back in the 1960s. During that time, the farm grew primarily a mix of soybeans and grains. For a child, it was a great way to grow up. So later, when Watkins and her fiancé took over the farm, they knew they wanted to continue the tradition.

“Our goal was about preservation even more than about gardening,” she said. “We wanted to protect these special parts of Maryland and keep them alive for not only our own child but for everybody else’s children as well.”

Why choose lavender? The couple was looking for a sustainable perennial that deer wouldn’t eat and one from which they could make products for sale. Lavender fit the bill — not only for its drought-tolerance, but also for its many decorative and culinary uses. As the farm grew in popularity, the couple added bees for pollination. And today, the farm boasts nine hives with over 40,000 bees in each, all producing lavender honey.

In recognition of Watkins’ fiancé’s Latin American roots, they named their farm Soleado, signifying sunny or ‘baking in the sun.’ As it happened, in their first year of operation, Watkins says they found themselves ‘dying in the heat’ as they got things established. Consequently, Soleado took on a new shade of meaning.

TOP TIPS FOR GROWING LAVENDER

At Soleado Lavender Farm, all of the plants are grown from cuttings, a practice most nurseries have adopted due to the lower germination rate of seeds. Watkins harvests both soft and hardwood cuttings in summer, strips all but two or three leaves at the top then dips them in a root hormone to encourage propagation. Not surprisingly, her top choice for root hormone is honey.

Honey bee

So as to give the roots plenty of space to develop, Watkins then plants her cuttings in a ‘bulky’ growing medium composed of Leafgro and perlite. Later, she transfers them to 2” plastic pots.

Once potted, the cuttings spend up to 8 weeks in partial shade or in the greenhouse (under shade cloths) until substantial roots begin to appear. In due course, the new plants are moved to the field. Watkins noted that if the cuttings are planted outside first, the process usually goes faster.

THREE IS THE MAGIC NUMBER

According to Watkins, three is the magic number of years it takes for a good-sized plant to develop. After that, it may continue to grow for another four. What happens around year seven, I asked? If taken care of properly, lavender can live for anywhere between ten and twenty years.  And incredibly, some historical properties boast plants that are over 80.

Lavender border along stone steps

A great combo, hydrangea and lavender

Regardless of age, once established, lavender is a sun-loving plant. This explains why no variety can tolerate shade and still produce flowers. Once the flowers are harvested, Watkins sprays the plants’ roots with fish emulsion for fertilizer. “We need to fortify them after they’ve put all that energy into blooming, “ she said.

GROWING LAVENDER IS A LOT ABOUT THE CUT

There is much conflicting information about when and how to cut back lavender. Watkins freely admits that her method might not suit everyone, but at Soleado Lavender Farm, they prune their plants two to four times a year. She shears her crop like sheep, cutting back all new growth each time the plants flower. This process begins almost as soon as the cuttings are transplanted.

Growing cutting back lavender

Cutting back encourages new growth

Cutting back not only encourages new, dense growth, but also helps mitigate lavender’s annoying tendency to open up in the middle. It also improves the overall looks of the plant and enables it to better survive the winter. Further, it redirects energy into developing strong roots, which according to Watkins, results in a thicker, healthier plant.

At Soleado Lavender Farm, however, they never prune anything thicker than a pencil. And they avoid old wood. Watkins does NOT recommend cutting back old woody stems. If you absolutely must, she said to trim them back just to where the first bunch of leaves start on the bush.

They stop all cutting by the end of October.

SHREDDED MULCH: LAVENDER IS NOT A FAN

Along with lots of sun, lavender prefers to stay dry. Ironically, once of the main threats to its survival comes in the form of mulch. According to Watkins, shredded mulch is the biggest offender. Since it often harbors mold spores, this kind of material can spell death for lavender.

“What seems to really kill them is the mold spores that come in on shredded mulch,” said Watkins. “Given the amount of humidity we have (in Maryland), it’s really important to stick with a dry medium.”

If you’re using shredded mulch in the rest of your garden, Watkins advises keeping it at least one to two feet away from your lavender. At the farm, they use crushed bluestone instead (that they harvest from their driveway.) Other great options include white gravel and seashells, both of which have the added benefit of reflecting light back onto the plant.

White gravel mulch is great for lavender

White gravel mulch

WINTERING TIPS FOR GROWING LAVENDER

Many of us have lost lavender plants over the winter. However, Watkins said, “Getting your plants through the winter does not have to do with size or age, even little seedlings can make it through the winter. A temperature of anything above 0 degrees Fahrenheit is OK.”

Frozen lavender flowers

Frozen lavender

So what can we do to prepare for the colder months? The most important thing, according to Watkins, is to keep plants trimmed and thick. The thickness (or thatchiness) is what keeps the snow and ice out of the plants. (Although snow doesn’t seem to be as bad for lavender as ice.)

In short, it’s a matter of creating a plants that have a good smooth cut on them so they become their own insulation.

Recently, a new lavender introduction called “Phenomenal” is showing amazing cold hardiness, retaining its leaves all through the winter. 

NO SIGNIFICANT PESTS OR DISEASES

Not only are its water needs low, but lavender also is resistant to most pests and diseases. Watkins says occasionally she’ll observe spittlebugs on her plants, but that’s about it. The main concern is lavender’s super susceptibility to mold spores caused by humidity. As I noted above, the best thing you can do for mold is to practice prevention.

Another great plus to growing lavender is that deer hate it, although Watkins observed that “Sometimes they’ll pull the young plants out of the ground, ‘Just because.”’

Deer won't eat lavender

Soleado Lavender Farm grows a mix of English, French and Spanish lavender varieties. They’re always experimenting with new strains and each year discover clear standouts. These days, Watkins is loving the “rabbit ear petals” on the flower tops of Spanish lavender.

Spanish lavender flowers

Spanish lavender

To learn more about Soleado Lavender Farm, its tours and lavender-based products, click here for the official website.

Updated March 2021