It`s hard to survive summer without it, yet too much of it causes nearly as much fretting. The it is shade, and the fretting occurs over a dirty subject, the bare soil at the base of those shady trees.
Shade shields us from the heat of summer, but the more there is, the less we can grow in its wake. Some of our more desirable trees-Crimson King and Norway maples, most of the oaks and the willows, for example-cast a virtually impenetrable shade on the ground directly below. It usually means thin, spotty grass in that area and yearly reseeding expeditions to try to get something to grow there. Most often it means mud in wet weather and a place for the kids to get dirty anytime. Roots often snake across the top of the soil.
Trees are treated differently in urban and suburban landscape settings than they are in their native forests. Most often, a tree is surrounded by another piece of the landscape puzzle; so what is planted near it becomes an aesthetic feature. But we have to take extreme care when cultivating around trees because roughly 70 percent of a tree`s roots are in the top 8 inches of soil.
Still, trees don`t have to be treated as a liability, argues Pat Welsh, a garden writer and television personality. Her solution involves building a low wall around the tree, potting shade-loving annual flowers in plastic pots, placing the pots inside the barrier and mulching the whole project so the pots don`t show. She calls the project a ”tree surround.”
”Where there are large areas that are filled with invasive tree roots, it is absolutely impossible to grow anything,” Welsh says. ”Many places would look marvelous except for the roots.”
She uses fir bark for her mulch because of its dark color and availability in Southern California, where she lives; other types of bark chips are more readily available here.
”I look for good plants at reasonable prices or buy small ones and pot them into 8-inch pots,” she says. ”I use plastic pots because they grow more evenly and it`s easier to hide the pots.
”I thought I invented this method, but I found out it has been done for centuries-I saw it at Versailles,” Welsh says. ”It probably dates back to Roman times. It`s a very adaptable system.”
Building a wall
While Welsh uses rocks to piece the wall together, she says railroad ties, broken concrete or brick can be used to make what essentially is a raised bed. ”Often you can get broken concrete for the cost of the trucking, and it`s a good way to recycle it,” she says. ”You can buy brick quite reasonably, use a little concrete and make it a permanent part of the garden.”
She emphasizes that planting should not be done close to the trunk and that mulch should likewise be kept away to keep water from settling against the bark and rotting the tree`s natural protection.
For winterizing, the pots can be pulled from the mulch when the plants die. She recommends renewing the top of the mulch each year, but once again using the holes where the pots were the previous year. In this favorable growing condition, the tree roots will grow up into the mulch, defining where the pots can be placed.
As for plant choices, ”impatiens and begonias are ideal, but you can use any other types of plants that do well in shade,” she says. ”Geraniums do well in partial shade and there are some beautiful new varieties out.”
A videotape called ”Solving Landscape Problems,” which includes Welsh`s step-by-step instructions for building a tree surround, is available for $19.95 plus $3 for shipping from Better Homes and Gardens, Dept. 279711, Box 11430, Des Moines 50366-1430; phone orders: 800-678-2699.
A second approach
Welsh`s solution works where shallow roots choke out other plants, but most problem situations are caused more by the shade created by a canopy of luxuriant foliage. Using a little ingenuity in choosing plants and providing a little extra maintenance will result in a lush setting where there once was only mud.
Cathy Walker, horticulturist with Martin Associates, a landscape design firm in Vernon Hills, says many types of plants thrive in these shady situations. Among them are hostas and ferns, which are perennials that die back in winter; and groundcovers that hold their color in all seasons.
”I`d plant right into the soil by hand, digging small holes,” she says. Her favorites among groundcovers include ajuga, vinca (periwinkle), goutweed, wild or European ginger, moneywort, purpleleaf wintercreeper and the several varieties of epimedium.
Two popular choices, ivies and pachysandra, stay green through winter but may suffer leaf burn if too much sun hits them after the overhead canopy of leaves drops.
”I`ve never grown Serbian bellflower (Campanula poscharskyana). But our plant buyer here really likes it, and it is drought- and shade-tolerant,”
Walker says. ”Leadwort is real pretty and blooms in August.”
Pour on the water
Because the new plants are competing with the tree for water and nutrients, Walker advises watering them more frequently than other parts of the garden in the first year or so after planting. When planting what you hope will be a solid mass of groundcover, use a diamond pattern for spacing and weed frequently in the first year or so to give the plants a chance to spread. It may take three years for some plants to fill in and create the desired effect.
When using any kind of planting that meets a turf area, define an edge between the two, Walker says. ”Whether you make a shallow edge or define it with something like brick, you should define the space and it shouldn`t follow the edge the shade has created. If you go from bare ground right into a nice lawn, it looks like heck.”
Color is another consideration. ”Impatiens are good for color if you choose the whites or pastel shades,” she says. ”If you have hostas, you can choose the ones with white on their foliage and white flowers-anything that will lighten up the area, not darken it with dark colors.”
Watch those roots
Trees such as silver maples and white poplars will have the shallowest root systems, often on top of the soil. Walker advises planting around large roots that come to the surface. ”Just one could be 25 to 50 percent of the tree`s roots,” she says. ”If you cut it off, it might not be noticeable immediately, but it may kill the tree down the road.”
Some trees, such as ”horse chestnuts, river birch and beech should be kept low-branched to keep the roots shaded,” she says, meaning the lowest branches should not be pruned off. ”By nature, you shouldn`t grow grass under them; you should mulch or do a planting there.”
Other types of trees can cause problems if low branches are not removed. Walker lists honeylocust, sugar and red maples, ash, ginkgo, hackberry, the decorative pears and most crabapples as those that should have their lower branches removed for a taller crown.
For all of the fretting over landscape trees, it came as a surprise to hear this same set of concerns for a stand of dense trees at a vacation home. What can be planted under them? The soil is hard as a rock, so can I put a truckload of topsoil in there? Can I use a tiller to break up the top several inches of soil so something will grow there?
The questions were those for a landscape situation, not for a forest.
Those trees are obviously happy or they would not have reached maturity. Mother Nature will visit this fall with a covering of leaves, the best thing that can happen to that barren ground.
Leave them and enjoy.
