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 →
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 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.)
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.
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.
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.
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.
When children aren’t getting along, parents know it’s time to divide them. The same goes for perennials that refuse to 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 →
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.
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.
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.
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
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.”
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.”’
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.
It’s that time of year again when we all head out to buy annuals for our containers. And the flowers always start out looking gorgeous. But, in no time the blooms fade and the stems turn long and leggy. As a garden designer, I find this is one of the most frequent questions I am asked: How do I keep my potted plants in shape all summer? Continue reading →
Let’s face it. It’s hard not to stress when your daffodils start popping up mid-winter. As weather becomes more unpredictable, early growth is becoming more and more common in spring bulbs. Not to worry, though. Your plants have seen it all before. Moreover, they’re built to handle a few temperature swings.
THE UNDERGROUND WORLD OF BULBS
To understand why spring bulbs can weather a little premature growth, it helps to take a peek underground.
Botanically speaking, a bulb is a short stem surrounded by fleshy leaves that store food during dormancy. As soon as you plant it in the fall, a spring bulb starts growing.
Each bulb has five major parts: a basal plate, scale leaves, protective tunic, a flowering shoot and lateral buds. The action begins in the basal plate. During the winter months, roots emerge from this modified stem to penetrate the soil.
As they develop, the roots absorb water and other nutrients that they store in the scale leaves.
In some flower species like alliums, a thin papery covering called the tunic keeps the scales from damage or drying out.
Papery thin tunic keeps bulbs from drying out
The scale leaves provide food storage, and they also protect the flowering shoot. This vital part of the bulb contains all of the future leaves and flowers. During the winter months, the flowering shoot slowly grows upwards within the bulb, eventually developing into a stem.
Finally, at a pre-determined time in the spring, the leaves break through the soil. Then, approximately one month later, the flowering shoot begins to appear.
At this stage in the process, the key thing to remember is: the flowers develop independently of the leaves.
This means that even if your bulbs (specifically, leaves) come up early, the flowering shoots still need time (between 5 and 7 weeks) to develop. And before that happens, your bulbs have most likely weathered the warm spell and resumed dormancy.
So if you see leaves poking up out of the ground too early, don’t worry. A cold snap may cause them to yellow and die back, but the bulb will wait things out and send up new growth once things warm back up again.
WAYS TO STOP YOUR BULBS FROM COMING UP TOO EARLY
There are a few strategies, however, that you can implement now to slow things down while providing an extra layer of protection to the flowering shoot.
1. COVER YOUR PLANT
Covering the soil around your spring bulbs will help insulate them against extreme winter weather like frigid temperatures and drying winds. Try mulch, straw, bark chips, leaves or pine needles.
Or, if the plant is budding too early, try draping a cloth over it (securing it above the plant with stakes.) Remove the drape during the day so the foliage can absorb sunlight to warm back up.
2. WATER DURING DRY SPELLS
If there’s been a dry spell for an extended period of time, a little extra water during the day helps bulbs grow. However, make sure your soil has good drainage. Bulbs can rot if they receive too much water.
3. IF FLOWERS START TO APPEAR
If the weather continues to stay unseasonably warm, your spring bulbs may start to produce flowers. Don’t worry. Even if frost kills off some of the initial buds, it usually won’t affect flowering in the coming months. And it won’t destroy your bulbs. They’ll still flower next year.
4. PLANT BULBS LATE IN THE FALL
The later in the fall you plant, the longer the bulb will take to sprout come spring. Wait until the temperature is cold enough (40°F or below at night) to plant your spring bulbs to ensure they’re fully dormant. Here in Maryland, I plant my daffodils in November.
Finally, make sure to plant your bulbs at three times their height in depth with the base down and the bud up. Planting bulbs too shallow makes them vulnerable to frost heaves and can lead to premature growth. And planting them upside down can stunt their growth.
For a list of ten popular spring bulbs and when and how to plant them, click here.
Author’s note January 2020:According to Science News, there is growing evidence that, in general, warmer springs are bringing earlier spring flowers. This in turn will result in longer growing seasons and drier summers. (This does not, however, mean daffodils in January.)
Here in Maryland we are having an unseasonably warm winter. In fact, it’s 65 here today on February 3. Below is a photo illustrating the state of my daffodils. (The leaves are about 3″ tall.) I’ll keep you posted as to their development.
My own daffodils on February 3
Same daffodils on February 24 – all foliage, luckily no blooms!
Looking for more information on daffodil care? I posted an article this week (February 2020) answering five top questions posed by my readers. Join the discussion!
You could say that evergreens are the stars of cold weather, instantly infusing drab winter landscapes with color and texture. When well sited, watered and fed, most can stand up to the harshest of conditions. Still, some evergreens are less equipped than others to battle icy winds and harsh winter sun. These are the plants that can benefit from a little extra TLC to prepare them for colder temperatures. Continue reading →