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Mulch volcanoes are harmful to trees—here’s why.

April 18, 2023 • Leave a Comment

by Steve Turner

Mulching is one of the best things you can do for your plants if it is done right, but too much or improperly installed mulch can be a real problem.

The problem

The common practice of mounding mulch against the trunk has proven to be a fatal one for many trees. These often seen “mulch volcanoes” are perfect circles 8 to 12 inches thick (or more) piled against the trunk. They are actually creating more problems than they are solving.

What compounds the problem is that many of these trees are on commercial properties under professional care, and this has helped create the false impression that this is the proper way to mulch trees. Homeowners see this and imitate the practice on their own trees. The neat, clean appearance it gives a landscape is appealing to many. Actually, I have had several customers over the years ask me if there is a mold they can buy to make these volcanoes on their own trees! So in our quest for a beautiful landscape, we are unknowingly sacrificing the long-term health of the trees.

LEFT: Mounding mulch against the trunk of a tree can create problems, including wounds, decay, and girdling roots. RIGHT: Mulch should be placed in a ring around the tree, with the center around the trunk empty, like a wide doughnut. — **LEFT**: Mounding mulch against the trunk of a tree can create problems, including wounds, decay, and girdling roots. **RIGHT**: Mulch should be placed in a ring around the tree, with the center around the trunk empty, like a wide doughnut.

How does it harm trees?

The bark on the roots of a tree is much different than the bark on its trunk or branches. It is able to tolerate moisture as well as the lower oxygen levels in the soil. The aboveground portion of the tree, which starts at the root flares, has bark that contains tiny openings which are used to release gases and toxins from its system. On plants such as cherry trees or forsythias, these sites (called lenticels) are easily seen as tiny white dots or dashes on the bark. Because of this important function, trees can’t tolerate soil or mulch placed above its root flares. The lack of air and the presence of excess moisture prevents natural respiration from the bark and causes a build up of gases and toxins in the bark tissue.

The damage

If soil or mulch disrupts the respiration of the bark, the tree will usually respond in one of two ways. On thin-barked, young trees or species with naturally thin bark, like beech or linden, this disruption causes cankers (wounds) on the trunk. These appear as areas of dead tissue and provide an opportunity for decay to enter the tree. Other species will react by sending out additional roots from the trunk. These roots often end up circling around the trunk and become girdling roots in the future. Researchers are finding out that trees with girdling roots and excess soil and mulch build-up are much more prone to snapping off at the base in wind and ice storms. The longer the problem exists, the more damage occurs, and the chances of correcting it decrease.

Note that not all trees will respond in the same way—species, age, and health all need to be considered when trying to evaluate the effects of past damage. Most willow trees, for example, are very adaptable to a change of grade and often will show no problems at all.

Can the problem be fixed?

If caught soon enough, it can be corrected and tree will recover. However, upon root crown inspection, if it is found that large cankers have formed and decay is present, or if the tree has developed extensive girdling roots, it might be wiser to remove and replace the tree than attempt to save it. During the root crown inspection, arborists use a high pressure air device called an “air spade” to safely remove the excess soil and mulch without damaging the root system. Once the soil is removed, there is a clear view of the buried trunk and roots. Then the damage can be evaluated, and a decision made as to which roots to leave and which can be safely removed. It is very important not to remove too much too soon or the tree will be shocked. Sometimes the work will have to be done in stages over a couple years.

Proper mulching

While it is common to see 4 to 6 inches of mulch around a tree, this is usually too much. I would suggest 2 to 3 inches placed in a ring around the tree with the center around the trunk empty, like a doughnut. How wide to make the ring is up to you, but the bigger the better. Trees don’t like to compete with lawns for nutrients and water, and the more mulched area you can give them, the better off they will be. Mulched trees have fewer problems than trees growing in lawns. Even a small, 2- to 3-foot ring can make a big difference. The mulch creates a more natural growing environment with its organic material breaking down and supporting vital soil microbes. Other benefits include increased moisture retention and cooler soil temperatures, both of which favor optimal root growth.

If done properly, mulch is a great asset to your landscape and aids your trees during summer drought periods by maintaining soil moisture. It also helps insulate the roots during the winter months, which allows them to remain active longer through the seasons.

Steve Turner, Certified Arborist, is from Arboricultural Services (248-259-8420).

ELSEWHERE: Mulch overload!

Growing vegetables in containers

April 18, 2023 • Leave a Comment

by Jeff Ball

Many homeowners live in a situation where there is insufficient space for even a small veggie patch. Those folks should consider growing vegetables in containers that can be placed almost anywhere as long as they get 8 hours of full sun.

Containers can be used to grow all the salad ingredients: lettuce, carrots, cabbage, cucumbers and tomatoes. Other popular vegetables enjoyed by most everyone are also easily grown in containers, including green beans, beets, Swiss chard and zucchini squash, just to name a few.

There are really just three criteria for the container used to grow vegetables: It must have plenty of drainage holes in the bottom, it must be at least 12 inches deep (deeper is better), and there should never be real soil used as a growing medium. All containers should use a soilless potting mix because it has no weed seeds, carries no disease spores, and drains very well. A good potting mix can be used for years, although it is wise to renew it each spring with some fresh compost and additional potting mix.

Finding containers for growing vegetables is not that difficult. Sometimes you can find some that do the job and are free for the asking. Just keep your eye out. I once spotted lots of used plastic barrels at a food processing facility. Sure enough, they were happy to get rid of them. I got four barrels, cut them in half with a saber saw and drilled a dozen holes in the bottom of each for drainage. That gave me eight large containers that I filled with potting soil and grew a nice harvest of potatoes.

A common container that is effective, but not free, is a whiskey barrel cut in half and sold in many garden centers. Again, you need to drill additional drainage holes, but because of their size, you can grow almost any vegetable in those devices. Tomatoes do especially well because there is so much space for their rather large root systems.

Years ago, I visited a serious vegetable gardener who lived in a row house. These connected houses have tiny front yards and often no backyard. He had a significant garden growing in over 50 plastic milk crates which he had appropriated for what he considered a “higher” use. He lined the crates with black plastic bags with holes in the bottom and filled them with potting soil. The colorful boxes filled his front yard, his front porch, a second floor balcony he built for holding more boxes, and on a platform he built on top of his garage.

I asked him if he had any complaints from the neighbors since his garden, while obviously productive, probably did not add much to the aesthetics of the neighborhood. He said he solved that problem by sharing fresh vegetables with his neighbors—a gardener with some political skills.

All of these containers I have described require watering each day or two by hand. Unlike the soil in the garden, a container filled with plants does run out of water more frequently and must be watched every day. That said, there are self-watering containers available that significantly reduce this worry of missing a watering need. These products are designed specifically for growing vegetables and several have been on the market long enough to have proven that they work well.

Nothing tastes better than homegrown vegetables and those grown in a container can taste just as good as those from a garden.

Jeff Ball has authored eight books on gardening, vegetables, and lawn care.

ELSEWHERE: MSU Guide to growing vegetables

Cut and come again vegetable harvesting technique

April 4, 2023 • Leave a Comment

**By harvesting just the outer stalks of the chard, it will continue to send up new shoots for later cutting.**

What do leaf lettuces, kale, Swiss chard, spinach, broccoli, and cabbage have in common? They are all examples of “cut and come again” vegetables. What exactly do we mean by that? Well, as the name implies, it is a vegetable that can have edible portions cut off, but will continue to grow and produce more portions that can be cut again at a later time. Usually, leafy vegetables that grow as a rosette (in a circular fashion or from a central point) are most likely to be cut and come again. Rosette-type plants include: broccoli, Brussels sprouts, cabbage, kale, leaf lettuces, spinach and Swiss chard, among a few others.

Many gardeners are probably familiar with cutting just the outer leaves of kale, spinachand leaf lettuce, so that the plant continues to produce fresh leaves that can be cut again a few days or weeks later. This helps extend the harvest without adding more plants to the garden. Eventually the plant will bolt (go to seed), at which point the vegetable will no longer produce the sweet edible leaves you want to cut, and the plant will need to be removed. It is also possible to cut the entire head of leaf lettuce providing the cutting is done about 1-1/2 inches above the crown, the growing point of the plant. If you cut off the crown, you may as well remove the whole plant.

Swiss chard and beet leaves also grow as a rosette. By harvesting just the outer stalks of the chard, it will continue to send up new shoots for later cutting. If you like to eat the greens on a beet, then you can harvest a couple of the outer leaves from each plant. When you cut the outer greens, leave about an inch or so of the stem on the beet.

While broccoli, Brussels sprouts and cabbage are also rosette plants, we don’t think of them the same way as most of the loose, leafy plants. Probably because we are harvesting the flower head of broccoli, the large head of the cabbage, and the small buds of the Brussels sprouts. However, done correctly, these vegetables will also continue to produce more for harvesting.

For Brussels sprouts, harvest from the bottom up. Cut the larger heads that develop at the bottom and allow the buds higher up to continue developing, then harvest as they grow. If you cut the rosette tip of the plant, the sprouts will tend to mature at the same time. For broccoli, if you cut the terminal head, side shoots will develop. They will not be as large as the main head, but will continue to be produced for several weeks. Lastly, for cabbage, cut the large central head, leaving the outer leaves and the root in the ground. Wait a few weeks and you should begin to see smaller heads forming at the base of the leaves that were left. These will grow into small cabbage heads, just a few inches in diameter, but sweet and delicious in soups, stews or salads.

Think of “cut and come again” as a type of plant pruning. As with all pruning, be sure that your cutting tool is clean and sharp. Take care not to cut the growing crown. Cut the mature outer leaves, preferably while they are still a little young, to help maintain the quality of the successive cuttings. Use care to maintain watering to reduce stress on the plant. Eventually all good things come to an end, so when the cuttings begin to lose flavor, the plant loses vigor, or seed formation (bolting) begins, the harvest is over and it’s time to grow something new!

Mary Gerstenberger was the Consumer Horticulture Coordinator at the Michigan State University Extension in Macomb County, MI. For vegetable and gardening information from MSU, visit www.migarden.msu.edu.

Call the toll-free Michigan State University Lawn and Garden Hotline at 888-678-3464 for answers to your gardening questions.

Elsewhere: Use this harvesting technique to have a continuous supply of vegetables during your growing and eating season.

Digital Editions

The problem

How does it harm trees?

The damage

Can the problem be fixed?

Proper mulching