Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: THURSDAY, October 21, 1993 TAG: 9310210188
SECTION: CURRENT PAGE: NRV-9 EDITION: NEW RIVER VALLEY
SOURCE: Joe Hunnings
DATELINE: LENGTH: Medium
The right tree in the right place not only assures a lifetime of satisfaction, it also keeps maintenance costs low.
In selecting that "right" tree, your first consideration must be what the tree needs.
In other words, what environmental factors limit the ability of a particular tree species to thrive?
Minimum temperature
The lowest temperature of the year limits the range of many trees.
The familiar "hardiness map" has zoned the country based on average annual minimum temperature.
Low temperatures, especially if they come suddenly, can freeze and kill the living cells in trees.
Select a species suitable to the zone where you live. The New River Valley is in zone 6 of the USDA plant hardiness zone map.
Moisture
Each species can tolerate wet or dry growing conditions to a different degree. Special attention must be given to your selection if the site periodically is flooded, subjected to very dry conditions, or is continually exposed to the drying effect of wind. Watering, of course, can modify a dry site, but even when you irrigate it is important to know the optimal soil moisture requirement for your species.
\ Tip: Because evergreens give off water (transpiration) from their needles all winter, it is important that they are well-watered in the fall before the ground freezes. Also, do not over-water trees. They will "drown" if the soil is kept too wet. With the heavy clay-type soils often found in the New River Valley, water deeply, but no more often than seven-to-10-day intervals during dry summer weather.
Light
Shade tolerance is the term foresters use to rate the light requirements of each species. Some species, such as white birch or most pines, require full sunlight. They are shade intolerant. Tolerant species, such as most maples, hemlocks and lindens can do well in shade. Others, like white oak, are somewhere in between and are referred to as having intermediate tolerance. Don't make the mistake of planting your tree where it is mismatched with its need for light.
Pests
Every locality has its problems with a particular insect or disease. The best way to avoid trouble is to avoid the species that host these pests. In some cases, it is possible to buy varieties that have been bred for resistance to a disease. For example, some species, such as golden rain tree and ginkgo, are known for their natural resistance to most pests. Others, such as American elm, are just the opposite. The European white birch is extremely susceptible to the bronze birch borer, whereas the river birch is far more resistant.
Soil
Soil factors are probably the most overlooked when selecting a tree. Soil depth, structure, and pH, in addition to soil moisture, can make the difference between success or failure after planting. For example, deep-rooted species will need adequate soil depth for their structural roots, whereas shallow-rooted species may do all right on sites where soils thinly cover bedrock or a hard layer of clay.
Species that need light, sandy soil should not be planted in rocky or clay-type soils. Also, each tree species has a tolerance range related to acidity and alkalinity just as it does for shade. This requirement should be matched with the soil where you plan to plant.
Soils are often disturbed in urban areas and trees which would typically do well may struggle because of poor soil structure. Compaction of the soil because of heavy pedestrian or vehicle use often reduces a tree's growth and longevity.
Joe Hunnings is the Virginia Cooperative Extension Service agent for agriculture in Christiansburg. If you have questions call the Montgomery County extension office at 382-5790.
by CNB