Tidewater Gardening - October 2008
October - Dry Season and New Perennials
K. Marc Teffeau
There seems to be a considerable amount of plant dieback in the landscape and forest this fall. I have noticed, especially in the wooded areas, the number of mature oaks and maples that have died over the summer. We really have had two years of dry weather, so a number of plants have been stressed because of the lack of rainfall. We were hoping that tropical storm Hanna would have helped us out on the ‘Shore, but most of that rain went to the Baltimore-Washington area.
In addition, there has been a lot of new plant mortality in home and commercial landscapes, even shrubs and trees that were planted a couple of years earlier. Folks seem to forget that it takes several years for newly planted trees and shrubs to root out into the surrounding soil, especially if they were container grown.
Most homeowners think of spring as the best time to plant trees and shrubs in the landscape. However, even though it is currently dry, October and November are generally considered the best time for moving plants in the landscape. After the drought problems of this past summer, a number of landscape shrubs and trees have died and are in need of replacement. Garden centers and nurseries usually stock a good selection of woody plants at this time of year. However, if you do plant in the fall, remember to WATER in a timely and appropriate basis if there is not enough fall rainfall.
You can transplant deciduous trees and shrubs after they become dormant, usually after the first or second hard frosts. You can also transplant evergreen trees and shrubs earlier in the fall before they become dormant. The exception to fall transplanting is pine seedlings. They do very poorly when transplanting in the fall because they are not able to develop good root systems before the winter sets in.
When selecting accent plants for fall planting, consider their autumn color. Make a note of plants displaying outstanding fall colors as you drive around town or in the countryside. You may wish ti incorporate some of them into your own landscape.
Fall color can often be enjoyed for a much longer period of time than the plant’s flowers in the spring. For this reason, it may be more desirable when selecting trees and shrubs for the landscape to plan greater emphasis on their fall features.
Red is one of the dominant fall colors that we see in our temperate climate. Trees that turn red include dogwood, sweet gum and red and scarlet oak. Remember that fall color is more strongly influenced by the tree’s genetic makeup than by the environment, although the type of growing season the tree has been through has an effect on the intensity of the color.
Trees selected in the fall when they are in full color can be expected to produce the same colors in future years. Red maple is one of the standard trees for good fall color. Cultivars of red maple that display outstanding colors include ‘Red Sunset,’ ‘October Glory’ and ‘Autumn Flame.’
Shrubs with good red fall color include viburnum, winged euonymus and barberry. An excellent native shrub species that you might want to consider is the Virginia Sweetspire (Itea viginica, ‘Henry’s Garnet’). It is a medium-sized shrub that spreads by rhizomes, ultimately forming a large stand if left unchecked. This deciduous shrub is loaded with 2- to 6-inch-long racemes of fragrant white late-spring flowers lasting two to three weeks. Virginia Sweetspire prefers a moist fertile soil but is adaptable to full sun or partial shade. It has no major disease or insect problems and is tolerant of lew, wet sites.
When planting trees and shrubs in the landscape, be mindful of a couple of issues. Plant trees at least 6 feet away from sidewalks and concrete pools, so growing roots will not crack the concrete. Also remember the mature height of the plant. This will reduce maintenance problems in the future. To minimize the look of open spaces between new shrubs, plant a low-growing ground cover such as bugleweed or winter creeper.
October is a good time to do maintenance of the trees and shrubs in the landscape. While you can still identify them easily, prune dead and diseased branches from trees and shrubs. Old, fallen leaves many contain disease innoculum for next year’s plant infections. Remove any infected debris from around the plant’s base and dispose of it. We usually recommend mulching newly planted trees and shrubs to reduce weed problems and to conserve moisture. In the fall, however, it is usually a good idea to wait to mulch until after the soil temperatures have reached 32°.
Mulches applied too early can do more harm than good. Mulch is used to keep soil temperatures constant and prevent frost heaving, not to keep it warm. In October the trees and shrubs start to harden for the upcoming cold weather. To encourage this process, remove mulch from around the stems of shrubs and trees. This will also discourage mice and vole damage to the stems during the winter.
Conifers that have poor color or weak growth may respond to fertilizer applied between mid-October and mid-March. Light pruning of both needled and broad-leafed evergreens is recommended in the late fall to encourage a strong framework to help the plant overcome any snow damage. Remove any weak or crowded branches. Remember to water evergreen shrubs thoroughly before the ground freezes, especially if we have a dry fall. This is especially critical for those foundation plantings under the roof eaves. Many times they do not get the moisture that they need from rainfall.
Evergreens continue to lose water by transpiring during the winter, but when the ground is frozen, the roots cannot replenish the water lost through the leaves or needles. Also, hold a bagworm picking party in October to remove the bags from the trees. This will help reduce the amount of spring hatch from over-wintered eggs in the bags and help to reduce the amount of spraying you may have to do next year.
In the vegetable garden, October is clean up time. Remove any dead or dying plants. Compost the debris if they do not contain disease problems. Use a shredder, if available, to cut up the plant debris before placing it in the compost pile. This will encourage faster decomposing of the plant material. If you do not have a shredder and have only a small amount of materials, run it over with the lawn mower. This works very well if you have a bagging mower. Then rake up the cut material or empty the bag into the compost pile.
If the ground is dry and workable, and the garden site is not subject to soil erosion, consider doing a fall plowing and letting the ground lay exposed over the winter. Late fall tilling can help control insects, such as corn borer, corn earworm, cucumber beetle, squash bug and vine borer, because it exposes over-wintering insects to winter conditions. It also makes soil preparation easier in the spring.
Another alternative is to mulch the entire garden in the fall with straw to a depth of 4 to 6 inches. Then in the spring, only pull back the mulch in the areas that you plan to plant. You will need to do this a couple of weeks before planting, however, to give the soil time to warm up.
If you are looking for a couple of new perennials to add to your flower border consider Armeria (Sea Pinks) and Prunella (Self Heal). Two Fleuroselect (the European nursery growers) Gold Medal Winners are Armeria pseudarmeria ‘Ballerina Red’ and Armeria psudarmeria ‘Ballerina White.’
According to Fleuroselect these first-year flowering perennials are early and produce an abundance of beautiful ball-shaped flowers on short, strong stems from June to September. They are compact and uniform in appearance. In addition, they are heat tolerant. They also have a nice winter appearance with their rounded dense cushions that remain evergreen throughout the winter.
Prunella grandifolia, ‘Freelander Mixture,’ flowers early and in great profusion from May to October. It has very nice spikes of tubular purple flowers that will attract bees and butterflies. This variety will thrive in many types of soil and can be exposed to different growing conditions and soils. The plant is also compact and uniform.