One born every minute

Suckering trees and shrubs

By Amy McDowell

In horticulture, there’s one born every minute. And there I was in the front yard in the chilly knee-deep February snow, pruning the suckers from around the base of my spring snow crabapple. I had read that if you prune suckers during the winter months they don’t grow back as quickly.

As the weather warmed in spring, tiny red buds emerged at the base of the trunk, and soon enough skinny suckers were growing up at the base of the tree again. Exasperated, I realized I’d been had—the only thing that had delayed the new shoots was winter.

Suckers are not all bad. Most of my favorite shrubs have a suckering habit that results in a broad mound of growth and a beautiful shape when mature. There are a great number of suckering shrubs, including lilacs (Syringa species), Hydrangeas, Spireas, pussy willow (Salix discolor), serviceberry (Amelanchier arborea) and bottlebrush buckeye (Aesculus parviflora). Many of these form dense thickets that create wonderful privacy when used as hedges. Frequently, you can dig the suckers from around the base of the original plant and use them to extend plantings around the garden.

Staghorn sumacs (Rhus typhena) ablaze in red and orange right now, and elderberry (Sambucus canadensis) sucker to form large, open colonies. Both are fairly aggressive for a small garden, but regular lawn mowing at the edge of the colony is all that’s needed to fight back their spread.

Suckers are a sign of a plant’s genetic vigor. A non-suckering shrub like purple-leaf sand cherry (Prunus cistena) can fall prey to collar rot in heavy clay soil, but if it had the ability to sucker, young new stems would keep the shrub alive as the older stems succumbed. If sand cherries suckered, it would vastly improve their durability and longevity in central Iowa landscapes.

Despite all of the great suckering plants out there, it’s still tough to come up with an advantage to the raggedy suckers at the bases of crabapple trees. Tender rabbit fodder, I guess, to slow their attacks on the tasty trunk bark.

Trees and Construction

Building your dream home on that wooded lot

By Amy McDowell

Wooded residential lots cost thousands more than treeless lots, but if those trees aren’t protected during construction, they can be severely damaged. Often the damage isn’t visible and the slow physiology of trees means they may live for four to seven years after construction crews have left the site, slowly spiraling into decline and finally death.

Soil compaction from heavy equipment and building materials is the most common damage. Ninety percent of a tree’s roots are within the top twelve inches of soil. Soil compaction may crush or tear the fine roots, but the loss of air space within the soil profile can be long lasting and even more devastating. Soil organisms can take decades to loosen compacted soils and return them to a healthy environment for tree roots.

The most important step to protecting the trees on your building lot is to ring them with a barrier that is not easily moved by construction crews. Metal stakes and bright orange snow fence works well. Place the barrier at least one foot from the base of the trunk for every inch of trunk diameter. For example, a tree with a two-foot diameter trunk must have a barrier at least 24 feet from the trunk.

Even after construction is complete, continue to guard the root zone. Don’t let a finish grader add or remove soil within the barrier zone. If you seed or sod the new lawn, use care not to drown the tree by irrigating too frequently. After the turf is established, water no more than once or twice a week.

A three-inch-deep mulch ring around the tree will protect the trunk from mower and string trimmer damage, and the wider the ring the better it is for the tree’s roots. Some arborists say a mulch ring that runs clear to the drip line of the branches would be a tree’s dream-come-true, although they realize that much mulch is unrealistic for most homeowners.

For large construction sites with complicated traffic patterns around trees, you might want to consult with an ISA certified arborist on how best to protect the trees. Information is available at www.isa-arbor.com or 800-ISA-TREE.

How NOT to trim a tree

Tree Topping is a Tragedy

By Amy McDowell

“Forfeit his hand, he who beheads a tree.” John Evelyn, Sylva, published in 1664.

Those words were written 347 years ago, but incompetent morons are still topping trees today. My heart lurches with horror when I see a tree butchered like the one in this photo.

(Photo by Larry Costello)

Trees do need pruning from time to time, but they NEVER need a severe heading back or topping. In fact, a tree will never fully recover from being topped. It will scramble to replace all of that food-producing leaf surface, but the rapid new growth is always weaker.

“Don’t do big, drastic pruning once every 15 years,” says Dr. John Ball, a professor of forestry at South Dakota State University. “Tree care should be life-long and low-intensity.”

At a recent arborist conference, Ball shared his advice on tree care. Training young trees is ideal, because you can set them up to live a long and healthy life. Most often, however, people wait until the trees are mature and then prune them. “You cannot make a tree healthy by making it smaller,” writes Dr. Alex Shigo. And over thinning the canopy, says Ball, is like bleeding a tree to death. “Branches are independent, not parasitic. Each one must produce its own food.”

ISA Certified Arborists can look at a tree and recognize what to prune. You can trust that an ISA Certified Arborist will do what is best for the tree. They sometimes laugh that their clients expect to see a huge pile of tree trimmings when they are done working. A trustworthy arborist is one who is most concerned with the safety and health of the tree and not concerned about creating a large pile of brush to impress their clients.

There are more than two dozen ISA Certified Arborists in and around the Des Moines area. You can find arborists in your area by visiting www.TreesAreGood.com.

I’d like to thank Dr. John Ball of South Dakota State University for the inspiration for this column. The photo, taken by Larry Costello, was provided by the International Society of Arboriculture.

Trees are our Heroes

Super Trees to the Rescue! – Plant a tree for Arbor Day

By Amy McDowell

Crime fighters are standing sentinel over our homes, parks and gardens. But these heroes wear canopies of leaves and corky bark, not wind-cracking capes and spandex tights. It’s true: trees fight crime. Researchers at the Human – Environment Research Laboratory at the University of Illinois Urbana – Champaign have proven it.

When researchers Frances E. Kuo and William C. Sullivan began studying green space and crime statistics in central Chicago in the early 1990s, the Chicago Police Department (CPD) said they could predict the results. More landscaping equals higher crime, they said. Trees and shrubs can conceal perpetrators. Remove their cover and you’ll reduce crime, they predicted.

The CPD was wrong. In fact, the relationship between trees and crime was exactly the opposite: the presence of green space and trees around buildings reduced overall crime by 52 percent—that was 56 percent fewer violent crimes and 48 percent fewer property crimes during the 9 years of their exhaustive research project.

Trees apparently do much more for us than providing beauty, shade, shelter, wildlife habitat and resources like fruit, nuts, maple syrup and wood. In addition to increasing property values, converting carbon dioxide into oxygen and reducing storm water runoff, trees can dramatically reduce crime. So isn’t it time you plant one?

In Iowa, Arbor Day is the last Friday in April—that’s April 30 this year. However, many cities declare the following Saturday as their official Arbor Day to promote community celebrations and tree planting activities.

To plant a container or balled and burlapped (B & B) tree, first brush back the soil on the top of the tree’s root ball to find the first major roots. To get the planting depth correct, you’ve got to look for those roots because often when nursery trees are grown and prepared for sale, excess soil ends up on top of their roots. Because of this, trees are frequently planted too deep and they not only fail to thrive, but they often die. The planting hole should be just deep enough to place these roots at ground level.

Dig the planting hole at least twice the width of the root ball. If the soil is clay or compacted, three to five times the width of the root ball is better. Another option in heavy soil is to dig four or five trenches that radiate five feet out from the planting hole like spokes of a wheel. Fill the trenches with compost.

Set the tree into the hole. For B & B, remove the twine and as much burlap from the root ball as you can. Fill in the hole with the same soil you dug out, adding some compost if you wish.
Mulch with 2 to 4 inches of an organic mulch like wood chips, keeping it at least and inch or two away from the trunk. Water thoroughly and check the soil weekly through the first season. If it is dry, water it.

If you stake the tree, leave the supports on for no longer than six months. University research has proven that tree canopies need to sway in the wind in order to promote far-reaching anchoring root systems. Use canvas or burlap strips to tie the trees to stakes and check for girdling (strangulation of the trunk) every month until the supports come off.

This Arbor Day, invite a super hero to come live in your garden.

Amy McDowell is an Iowa Certified Nursery Professional. She has a degree in horticulture and has worked in the field for ten years. She lives and gardens in Polk County, Iowa.