One of the botanical ideas most of us have learned in the last few decades is the idea of “invasiveness”—the non-native plants that, once introduced into an ecosystem, spread everywhere. Kudzu is the classic example.
Peter Barber, the partnership coordinator of the Kentucky Division of Forestry’s urban and community forestry program (www.forestry.ky.gov) shares his thoughts on the problem of ecological invasiveness. Tree of Heaven (also called stinking sumac) “can colonize our fields and woodlands,” Barber says. “Wherever they’re growing, a native tree is not growing.”
But trees that aren’t ecologically invasive can be harmful in a more subtle way, by a kind of invasiveness of the imagination—they reduce an ecosystem’s biodiversity by being used too widely.
Dena Rae Garvue, horticulture director at Bernheim Forest (www.bernheim.org), says, “Basically, maybe 20 to 25 trees are the most common for urban settings and you see them throughout” cities and towns.
Barber notes that while the pin oak is a fine tree, it’s been planted so widely (especially in cities) that there’s really not much point in planting another one. Kristopher Stone, director of the Boone County Arboretum in Union (www.bcarboretum.org) and blogger for Kentucky Gardener magazine, nominates the red maple as another overplanted species. “Not that we shouldn’t plant them, but you always want to have a way to avoid monoculture,” he says.
So let’s get more diverse. This article, based on recommendations from several Kentucky tree experts, suggests some trees that homeowners might like to plant. They’ve been chosen to bring some new, or at any rate less common, varieties to your attention. A good number are native trees; all of them are suited to Kentucky’s climate, are pest-resistant, and not invasive.
But don’t just take our list and head for the nursery. You’ve got a lot of work to do first. The cliché in horticulture is “the right tree in the right place.” But that simple formulation involves a lot of thinking.
The most important factor is to look into the future—to know how your tree is going to grow. “People purchase plants when they’re in a small container and they go, ‘Oh, I like this. It has beautiful architecture, I really like the bark, and the leaves are beautiful,’” says Garvue. “And they put it in the ground not knowing what it’s going to be like in 30 years.” Which leads to trees that fall onto your roof, or have to be cut in an unappealing “U” because they’ve grown up into power lines.
Indeed, where your utilities are located is the first factor to consider.
According to Barber, large trees (ones that will grow to be more than 40 feet tall) should be planted at least 40 feet away from overhead lines (electric lines being the most crucial); plant medium trees (growing 25-40 feet tall) 15 feet or more away.
Barber recommends having your utility company spray-paint or flag your lawn to indicate where underground utility lines run. This can be requested by contacting the Kentucky Call Before You Dig by simply dialing 811. All trees should be kept at least 10 feet away from the underground lines. All tree roots will grow as far as they can, following the path of least resistance. The soil around pipes tends to contract and expand, allowing water to condense on the pipe, and making the soil moister and more attractive to the probing roots.
Large-growing trees should be planted as far away from driveways, curbs, and sidewalks as possible—Barber recommends a minimum of 4 feet. And he says large- and medium-growing trees should be planted 10-20 feet away from building foundations.
Other considerations are whether the tree is suited to your type of soil and drainage, as well as a site’s exposure to sun and wind and the tree’s susceptibility to disease. It’s also worth thinking through what the tree will drop—some people don’t like the mess of cleaning up crabapples or plums; others are annoyed by the percussive dropping of nuts, especially when they put a dent in the new pickup truck.
Barber points out that many cities have lists of trees that are acceptable to plant (and other trees that aren’t approved). Any of the 38 Kentucky communities that participate in the Arbor Day Foundation’s Tree City USA program has a tree board that can be consulted about preferred trees.
Choose orientations that maximize the effect you’re going for—for example, having shade fall on the east and west sides of your house.
And then there are the aesthetic choices—all the multiples of shape, leaf, flower, and bark that a landscaper can use with a painter’s eye.
Will it be a shade tree? Is it providing fall color? Is it supposed to be a specimen tree, considered a standout that attracts attention? Or a foundation one—the plants that provide the framework for your landscaping? What “habit” (typical growth pattern) are you looking for? In other words, what look do you want—sweeping boughs, or weeping ones? Is the overall shape vaselike, columnar, or round? Are you looking for flowers, or ornamental bark?
Choose a tree that speaks to you and it will also shade and enrich future generations.
James Nold Jr. from March 2011 Issue John Crilly