In this month's expert interview, Guide to Shrubs, we continue our discussion with Penelope O'Sullivan, author of The Homeowner's Complete Tree & Shrub Handbook: The Essential Guide to Choosing, Planting, and Maintaining Perfect Landscape Plants. (Storey Publishing, 2007).
Guide to Shrubs
Shrubs can provide color and interest to landscaped areas around the home. They can also be used to divide areas on your property and provide privacy screens.
What are some considerations for planting shrubs around a home?
All the considerations for trees hold true for shrubs. In addition, think about using shrub masses to balance the architectural masses of the house.
Consider safety issues when planting shrubs around your house. Big shrubs in a foundation planting can dwarf a small house and create unsafe places for intruders to hide. Thorny shrubs near walkways can snag clothing and injure tots who fall against them. Planting evergreen shrubs too close to the walls of a house can cause mold and mildew to form.
Are there any plants that are just too invasive to plant in a landscape?
New Hampshire, my home state, has several common landscape plants including burning bush, Japanese barberry, and Norway maple on its invasive species list. My book lists the invasive tendencies of many different trees and shrubs throughout the country.
If you're in doubt about which plants are problematical in your area, check with your state's Cooperative Extension service.
Are there any trees or shrubs that are prone to diseases?
Certain disease-prone trees become more susceptible when stressed. Typical stressors include drought, late freezes and thaws, deer damage, and incorrect planting techniques. You can still plant these trees in your yard, but they require more maintenance and may need treatment from an arborist or early replacement.
One way to deal with this problem is to plant disease-resistant varieties. For example, roses are notoriously disease prone. Yet rose lovers who want low-maintenance, relatively disease-free roses can grow sturdy plants from the Knockout series or Crown Princess Margareta®, an apricot-orange English rose from David Austin. Similarly, 'Winter King' green hawthorn (Crataegus viridis 'Winter King') resists rusts and fire blight, diseases that plague many other hawthorns. Ohio buckeyes (Aesculus glabra) and European horsechestnuts (A. hippocastanum) are prone to severe leaf blotch, so it's best not to plant them in small home landscapes. For more information on plants to avoid in your area, contact your local master gardeners.
Can you suggest any plants to create an outdoor room or privacy screen?
I suggest planting evergreen privacy hedges. The best hedging plants for your site depend upon factors such as light, soil, climate, and the size of your lot. If deer are not a problem, then columnar Hicks yew (Taxus x media 'Hicksii') or Eastern arborvitae (Thuja occidentalis 'Holmstrup', 'Smaragd', or 'Techny' are possibilities. Deer-resistant Spring Grove giant arborvitae (Thuja plicata 'Grovpli') is terrific for year-round screening; it has shiny, dark, deer-resistant foliage and grows up to 24 feet high by 3 to 6 feet wide.
Many other conifers and broadleaf evergreens are suitable for year round screening. Also consider using hollies (Ilex cornuta, I. aquifolium, I. x aquipernyi), boxwood (Buxus), holly osmanthus (Osmanthus heterophyllus), and certain junipers (J. chinensis and J. virginiana) for screening with some deer resistance.
Is mulching necessary for healthy shrubs and trees?
I think mulching is one of the best actions you can take on behalf of your trees and shrubs. Mulching around them prevents lawn mower nicks on tree trunks, injuries that can lead to problems with pests and diseases. Organic mulches help protect them from herbicide damage, smother weeds, and improve the soil as they decompose.
Mulching conserves moisture and insulates the soil, keeping it warmer in cold weather and cooler and in the heat. Mulching also keeps plants clean by absorbing splashes of water, which would otherwise bounce off the bare soil and onto the leaves, stems, and trunks of woody plants. For best results, spread a 2- to 3-inch layer of mulch, making sure it stays a few inches away from the tree trunks.
For more information on planting shrubs, please read the following articles, in addition to this Guide to Shrubs: