Avoid design mistakes, from plant choices to lighting

WASHINGTON - Design errors can create a lack of harmony and comfort in your garden. Here are the most common landscape design mistakes.

• Not fitting in with your surroundings. Try to generally match your neighborhood. A wildflower meadow in your front yard might not be aesthetically pleasing if lawns cover the front yards of other homes on your street. Instead, have some lawn or a single species of low-growing groundcover, and plant wildflowers closer to the house or in the back yard.

On the flip side, you might live in a community with all-natural plantings. Manicured lawn edges and beds filled with rows of shrubbery wouldn't fit. This is a place for wildflowers or random woodland gardens.

• Planting before planning. You could design your garden in trial-and-error fashion, digging and moving plants and changing patio and other walk lines as work progresses. But it'll be a lot easier on your back if you first move the plants and walk lines with pencil and paper.

• Installing plants in a "one of each" fashion. When you bought mums last fall, did you have trouble choosing the colors you wanted and get one or two of each? This can happen from not planning before planting. The same colors should have been planted together. The bulbs you planted last fall should have been massed the same way, at least 10 of the same species and color together. You have to be strong-willed enough at the garden center to choose just a few colors and stick to your guns. This holds true for most plant choices.

• Installing plants without ascertaining mature size. It would be great to install a tree or shrub at the size you want. However, plants are dynamic, living, growing entities with a mind of their own. It takes seven to 10 years for shrubs to begin to reach their full potential, longer for trees. Placing plants too close together or against the wall of your house (unless you are training it to grow there) can create a maintenance headache and waste costly plant material.

• Using deciduous trees as screening plants. A lot of home gardeners leave lower limbs on trees because they offer screening. Except those that are so small that they never grow tall enough to have a canopy, deciduous trees are more effective when lower limbs are pruned and the understory is planted with flowering shrubs and perennials. Some of the trees that should be limbed up six feet or more are large shade trees, upright growing Japanese maples, flowering cherries, dogwoods, redbuds, crabapples, deciduous magnolias, stewartias and river birches. Prune the lowest limbs at the trunk just above their branch collar, or the flare at the base of the branch, as the tree grows taller; and always prune suckers, or water sprouts, as they grow from the base of the plants.

• Mulching beds too copiously with ornamental bark. People mistakenly think that ornamental hardwood bark improves soil. So in their efforts to enhance the landscape and soil, they pile it higher and deeper. Deep layers of mulch keep air, moisture and nutrients from reaching the roots and kill plants when piled against a tree's bark. Further, according to research by retired University of Maryland horticulture professor Frances Gouin, hardwood bark mulch spread four to five inches thick can cause manganese toxicity in soils. Use bark mulch sparingly to prevent weeds, hold moisture and give a clean, finished appearance to planting beds. Never spread more than a one- to two-inch layer.

• Designing stairs without considering lighting. This is often the least considered aspect of stairs. Light all steps from above without casting shadows that hide the walking surface. Homeowners usually think about how their decks and yards are lit, but not the stairs that get you from one place to another. The best time to see how lighting will look is to check it at night.

• Designing "trip steps." People generally do not notice a single step in a path. Where there are slight grade changes you're better off installing two low steps than one "trip step." Risers of varying heights in a set of stairs are also a good reason to walk cautiously. The disparities in height will throw users off balance and send them to the ground, even when the difference is barely perceptible. The most comfortable sets of stairs have six-inch risers and 14-inch treads on each step and at least two and no more than 10 steps without a landing.

• Shrubs or trees obstructing visibility at driveway entry. Many homeowners plant shrubs or trees to mark property entries and create privacy. But if you can't see 300 feet in both directions from your car before approaching the street, the plantings are making it difficult to see oncoming pedestrians or autos before pulling into traffic. Check your sight line from the driver's seat while your car is at the entry of your driveway.

Joel M. Lerner is author of "Anyone Can Landscape" (Ball 2001). Contact him through his website, www.gardenlerner.com.