Spread the word … and the mulch

Volcanic activity is on the rise in Kane County.

Volcanoes? Here? Yes, indeed, and they're killing trees in Kane County.

The volcanoes are made of mulch instead of lava. "Volcano mulching" is the all-too-common practice of piling mulch in an inverted cone up the trunk of a tree. Drive anywhere in suburbia and you'll see mulch volcanos along parkways, in yards and in gardens. Entire subdivisions are covered with mulch volcanoes. The intention may be good, but the practice is harmful to trees.

Mulching, when done correctly, offers many benefits to trees. Mulch mimics nature by creating a layer of organic material under the spread of a tree. In the woods, fallen leaves, branches and herbaceous plants cover the ground. This organic matter is called leaf litter - but it's a good kind of litter. It retains moisture, insulates the ground, slowly decomposes, and enriches the soil. There's an entire ecological system in leaf litter, complete with food webs, unique biochemistry, and microclimates.

In landscaped settings, the ground under a tree may be a thin layer of turf grass or bare soil. Mulch is added as a ground cover to achieve some of the benefits that natural leaf litter provides in the woods. It helps to hold moisture, suppress weeds, and insulate the soil from extreme heat and cold. It also protects trees and shrubs from overly zealous gardeners with lawns mowers and weed whips.

Often, mulch is used purely for aesthetics. People just like how mulch looks. It gives a neat and tidy appearance to landscaping. Some might say it's a control thing.

The volcano problem

Evidently, lots of people like the looks of controlled volcanoes. The problem is that volcano mulching takes the benefits of mulching and turns them into negatives. Water retention is a prime example. Mulch helps conserve moisture, but too much of a good thing is - well, not such a good thing. When piled up against the tree trunk, mulch keeps moisture where it shouldn't be. Moisture trapped on bark makes the tree highly susceptible to disease and decay. Bark can develop cankers, or wounds. Large limbs, leaves, and other parts of the tree above a canker die. Some volcano-induced cankers may girdle an entire tree.

Volcano mulching also wreaks havoc on root systems. It causes some roots to suffocate, reducing overall water intake. It also encourages roots to grow up into the mulch layer, instead of down into the soil. During drought years, roots need to tap deep into soil where the moisture is, but if they're up in the mulch layer they get little but air. Thus, the mulch intended to retain moisture may actually cause the tree to die of thirst.

Additionally, mulch volcanoes shed water like an umbrella. Even in years with lots of rain, an improperly mulched tree may not get moisture where it needs it, because the rain runs off the sides of the volcano.

Mulch volcanoes may turn "sour." This is caused by anaerobic conditions (lacking oxygen) created by thick layers of mulch. The organic material heats up, becomes highly acidic, and smells sour. This acidic mulch burns the tree's bark. This is especially harmful to young trees that haven't developed thick bark.

Another issue with volcano mulching is the type of mulch used. Not all mulch is created equal. The leaf litter in the woods is diverse (and definitely not neat and tidy). Mulch for landscaping comes in many forms and may include wood chips, bark, leaves, pine needles, or a combination of these. The composition of mulch is very important for plants, because it has unique chemistry, water retention properties, and decomposition rates. In nature, this is all taken care of, but a gardener must match the mulch with the need.

Just say no

With all the downsides of volcano mulching, why do people do it?

A horticulturist quoted in a Washington Post article explained, "Monkey see, monkey do." It's not clear when the practice of volcano mulching started, but when some landscapers began to do it, others followed suit. Homeowners saw it, and they thought that's what the pros do, so they copied it. And on and on it spread.

There have been efforts to correct the trend, but it's hard to kick a habit. City of St. Charles Public Works Manager AJ Reineking explained the city has made efforts to educate people by distributing fliers and demonstrating proper mulching in tree plantings throughout town. Not everyone has gotten the message, and the practice continues. "In our area it seems that people think it looks nice," he said, "and they expect landscapers to do it."

Our native trees are tough, and they've endured blizzards, droughts, tornadoes and floods over thousands of years. Volcanoes are a new challenge. The difference is that we can't stop blizzards and storms, but we can easily control volcano mulching.

Just say no.

Kick the habit.

Get out the rake, spread the mulch, and spread the word. An entire generation of trees will thank you for it.

• Valerie Blaine is the nature programs manager for the Kane County Forest Preserve District. Reach her at blainevalerie@kaneforest.com.

Proper mulching techniques

Select a mulch suited for your tree. Native trees do well with organic mulch from materials that are readily available. Every fall, Mother Nature provides a prolific amount of mulch in the form of fallen leaves. The price is right, and they're yours for the taking. You can break them down with your lawn mower before applying them.

Wood chips will often do the job nicely, too. Many municipalities offer free wood chips to residents, and some will deliver to your driveway. The Kane County Forest Preserve District offers wood chips for pick up at various times during the year. Check kaneforest.com for availability.

Spread mulch in a circle that approximates the drip-line of the tree. This means the area covered by the spread of the branches, or the shaded area under a tree at noon.

Apply two to four inches of mulch. It's better to go lightly, and add more later as the mulch decomposes. Remember that mulch should not "smother" the tree's roots.

Pull mulch away from the base of the tree so that it's not touching the bark. The overall mulch should look like a doughnut, not a volcano.

Replenish the mulch as it decomposes.

- Valerie Blaine