‘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 →
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. 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.
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 →
After 14 days without water, only the plants treated with vinegar survived. NIKEN
Lack of water is becoming an increasing concern both for human and plant life across the planet. Now comes the news that scientists in Japan have discovered that ‘watering’ plants with vinegar can help them adapt to drought stress. I don’t know about you, but I’m reaching for my white vinegar right now to see if my hydrangeas wouldn’t like a swig.
Last week, scientists at the RIKEN Center for Sustainable Resource Science (CSRS) published the results of a study that showed huge promise for thirsty plants of the future. Researchers revealed that they had stumbled upon a new biological pathway in certain species that sprang into action in times of water stress. By studying the pathway and the chain of chemical reactions within it, the scientists made a surprising discovery. They found they could induce greater drought tolerance in certain plants by growing them in vinegar.
Most of us are familiar with vinegar’s miraculous cleaning and anti-bacterial properties, but helping plants cope with drought? Now that is shocking news indeed.
My hydrangea showing signs of water stress
A little plant named Arabidopsis
It all started with a collaborative effort to understand the plant Arabidopsis, also known as thale cress. A relative of cabbage and mustard, this genus of small flowering plants was the first species to have its entire genome sequenced. As a result, it is considered a model organism for studying plant biology.
Perhaps most interestingly, Arabidopsis is also known to exhibit strong drought tolerance. This is due to a mutation to an enzyme called HDA6. Specifically, the mutation allows the plant to grow normally without water for extended periods of time.
Microscopic view of anther of Arabidopsis, also known as thale cress
HDA6 acts as a switch
Indeed, initial testing showed that when experiencing drought stress, Arabidopsis uses HDA6 to activate a biological pathway that produces acetate, which is also the main component of vinegar. The HDA6 enzyme acts as a switch, controlling which type of metabolic pathway is active. While most plants are busy using metabolic pathways to break down sugar for energy, Arabidopsis switches to this acetate-producing pathway to endure long periods when there is no water at all.
Clearly there was something going on. To find out how this switch works in times of water stress, scientists conducted an experiment. They grew normal plants under drought conditions, treating some with water, some with organic acids and others with acetic acid. After 14 days, they measured the results. Surprisingly, 70 percent of the plants treated with acetic acid were still living. Conversely, all of the other plants had died.
Microscopic view of stem epidermis of thale cress showing hairs and stomata
A link between acetate and drought performance
By measuring the amounts of acetate in the Arabidopsis, the team discovered there was a direct correlation between the amount of acetate the plants produced and how well they performed under drought conditions. Even more exciting, the team carried out the same experiment on rice, wheat and maize and these species’ tolerance increased, too, when grown in optimal acetic acid concentrations.
Close-up of rice plant
It goes without saying that the implications of this research are huge. In an increasingly water-stressed future, this discovery might offer a simple, low-cost alternative to other strategies like genetic engineering. Still, I’m not sure if vinegar will help my hydrangeas survive another scorching Maryland summer, but it’s worth a try. I’ll let you know.
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 →
There’s a fascinating image that has stuck with me ever since, years ago, I read the sci-fi novel Goodbye and Thanks For All the Fish (the fourth installation in the series the Hitchhiker’s Guide to the Galaxy.) In the novel, author Douglas Adams describes a four-walled house turned inside out. If you entered the house, you found yourself ‘outside’ in a green space, complete with lawn, benches and walking paths. If you exited the house, you found yourself ‘inside’ in a far less desirable place Adams termed the Asylum. Continue reading →