Wilson Bentley Digital Archives of the Jericho Historical Society/snowflakebentley.com
‘No two snowflakes are alike’ is a saying that many of us have grown up hearing. But few of us are aware of the man who coined it, a farmer from a small rural town in Vermont by the name of Wilson A. Bentley (1865-1931). Bentley was the first person to photograph a single snowflake, thus opening a window into this astonishing world of unique crystalline sculptures. 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.
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
A suburban meadow can free you from tiresome yard work
These days, many of us are searching for alternatives to conventional lawn and garden care, a chore that has become increasingly dependent on time and maintenance as well as pesticides and other poisons. Luckily, there’s a solution to the problem. Sustainable and chemical-free, it’s called the suburban meadow garden. Continue reading
Washington, DC’s 11th Street Bridge Park/Photo: OMA + OLIN Anacostia Crossing
There’s a movement afoot that aims to turn old infrastructure into public parks, breathing new life into spaces that have long since been forgotten. Of these, the transformation of an old rail line into a garden on Manhattan’s West Side (the High Line) is the best known. Now comes Washington, DC’s own variation, the 11th Street Bridge Park. Soon, the city’s first elevated park will be perched high atop the Anacostia River. Continue reading
Bumblebee pollinating mustard plant/ Photo: University of Zurich (UZH)
In recent years, there’s been a lot of buzz about pollinators, especially the fuzzy yellow and black kind. Now comes news that bumblebees not only help plants propagate, but they also have a positive effect on their size, fragrance and color. It’s all part of an experiment by researchers at the University of Zurich that proves bees do it bigger and better. Continue reading
“Even the sharpest ear cannot hear an ant singing” -Sudanese Proverb
(Red ant on Fijian palm leaf)
Just when you thought you’d heard it all, this week comes the revelation that a certain species of Fijiian ants has been growing plants for millennia. And they’ve been doing so for far longer than humans. The ants have been growing crops and establishing their colonies within them all while tending their own teeny tiny community gardens. Continue reading
Have you ever driven by a cornfield during a prolonged period of drought and asked yourself ‘How do these plants survive?’ Well it turns out scientists have uncovered a protein in plants that holds the key to why some survive and others don’t. It’s called ABA INSENSITIVE GROWTH 1 (ABIG1) and it may determine the future of plant growth in an increasingly waterless world.
As all gardeners know, working in the garden is not just about plants. Being outside with your hands in the soil makes you keenly aware of animal life, too. Over the years, I’ve gardened in tandem with a majestic blue heron, a band of three crows and a playful red fox. Now, with the arrival of warmer weather, I’m looking forward to the return of the purple martins.
Aside from being able to identify their houses (virtual mansions of the ornithological kind), I didn’t know much about these birds until recently, when my garden club hosted two members of a local purple martin society. Ever since, I’ve been scanning the skies for the colorful species. According to the experts, the first wave of birds will be arriving in my area soon.
Purple martin house
Of the eight swallow species, purple martins are the largest. The dark, bluish-black birds arrive in North America each spring, soaring on the jet stream from their native southern Brazil. It takes them about five weeks to fly the 10,000 miles, which is quite a feat for a bird that weighs only about 2 ½ ounces.
Female purple martin in flight
Like many neotropical birds, purple martins travel north in order to breed. The birds arrive at the height of the insect season, establishing themselves in colonies located close to water where there is the greatest food supply. In total, the migration can take up to 2 to 3 months to complete.
In Brazil, purple martins are considered a public nuisance, mainly due to their large numbers and preference for roosting in trees around central plazas. As a result, some municipalities have gone so far as to install sirens and other devices to chase the birds away.
In the United States, on the other hand, it’s a different story. Here, large groups of purple martins return each year to establish neighborhoods in man-made housing only. In fact, they are the only bird species that is totally dependent on human-supplied housing. Not only do they like people, but they actually prefer living in close proximity.
As a species, purple martins favor locations in wide-open terrain, usually in the form of pole-mounted martin houses or gourds. This keeps them out of reach of predators like owls and hawks that dwell in tree cavities. They’ll generally avoid congested suburban areas and instead roost in open meadows or fields located near lakes or other bodies of water.
Although just one male and female live together in a room or gourd, the highly sociable birds house together in colonies, where they interact as a unit, sharing food and singing to each other. All told, a group of houses or gourds can host as many as 60 to 70 birds over a 2-month period.
Purple martin pair
Now is the time of year when the first scouts (who are the oldest birds) begin arriving from Brazil to check out their nesting sites from the previous year. The scouts pave the way for the rest of the flock, which arrives 4 to 6 weeks later. Built like a glider, the birds can travel at speeds of more than 40 miles per hour.
And purple martins bring a whole new meaning to eating ‘on the fly.’ According to Mike Dickson of the Purple Martin Society of Frederick, Maryland, they only recognize food that is in flight, meaning that they primarily snatch insects in midair. Adept in performing complex aerial acrobatics, the birds even drink in the air. They accomplish this by flying low over lakes or ponds while scooping up water with their bills.
A female in flight
Indeed, you’ll never find purple martins foraging for food on the ground, or eating seed from a feeder. People who choose to feed the friendly birds will discover they’re quite open to the idea, but only if the food is flung to them. On occasion, human intervention is necessary when periods of cold or rain suppress insect populations. This can spell death to entire colonies.
One of only a few colony birds that love to sing, purple martins’ throaty chirps can be heard May through June during the breeding season. According to the Cornell Lab of Ornithology, males make a croaking song during courtship that can last up to 4 seconds. People say that once you’ve heard it, you’ll never forget it.
Males perform the dawn song
Purple martins sing in a combination of gurgles, clicks and song, with the loudest singing occurring before daylight. Males perform this dawn song possibly to attract other birds to the nesting site. Click here to hear a few of their beautiful songs.
All too soon, by the end of July or first week in August, the birds prepare to leave for their migratory roost. Many purple martin lovers describe this time as a sad one, when they awake to find the birds gone and their houses empty. It’s as if suddenly, the countryside has fallen silent.
Female purple martin
Once airborne, the birds fly south to a designated spot to roost before heading back to Brazil. Often they gather by the tens of thousands. In fact, the largest roosting colony on record was estimated to have 700,000 birds at one time. All told, there can be thousands of purple martins in the sky at one time, so many that they often show up on Doppler radar as giant rings.
Interested in attracting purple martins? Here’s a great article from the Purple Martin Conservation Association in Edinboro, PA, a non-profit conservation organization.
Aren’t they cute?
One of the many things I love about gardening is working alongside my many fuzzy, buzzing friends. Dutifully arriving on the job each morning, the bees hover beside me, yielding as one mass each time I shift position in the garden. Sometimes, I’ve been brave (or stupid) enough to touch one of the downy creatures, and they’ve allowed me to stroke them. Feeling the tiny vibrations of all that industriousness never ceases to amaze me. Continue reading
