Norm maintains there are several basic guidelines every homeowner should be aware of when purchasing plants. Brookings, SD is in Zone 4 for both heat and cold. most people only consider the cold hardiness of a plant and this is a critical mistake as heat tolerance is equally important. What is hardiness? Hardiness is defined as the ability of a plant to thrive in the site it is growing in, not just the ablility to withstand cold temperatures. In any given zone however, you may have micro-climates that vary and allow plants to survive from a zone south of ours; or may require a more cold hardy plant selection from a zone north of ours.
Soil structure and quality are also important, Norm says. The ideal growing media consists of 45% mineral matter(loam, silt, clay), 5% organic matter, 25% air space, and 25% water holding capacity. The site should come as close to these percentages as possible in the first 10 or more inches of topsoil. Also, check your drainage before planting by filling your test hole with water. The water should be gone in a few minutes. A good site should not allow water to stand. It should drain freely. An alternative to planting trees and shrubs into poorly draining, or thin soils, is to plant them on a berm. A berm is a raised mound of soil which gives additional depth of topsoil to your landscape. Successful berms are wider, not deep. A tree can be very happy in a berm that is 6 inches above grade, and only 6 feet wide. Keep in mind soil settles over time, so expect up to 40% of settling with a berm built out of good topsoil. Do not pack this soil or work it when wet as that destroys air spaces and removes your advantage to using a berm. If these requirements are ignored one can expect slower growth rates, poor root systems, and decreased ablilty to resist stress such as drought or disease.
The pH of the soil is an additional factor to consider in choosing the correct location. Certain plants that are hardy to Zone 4 may not be pH tolerant. The pH is a measure of the alkalinity or acidity of the soil. Most trees, shrubs, and perennials will tolerate a pH of 6.0 to 8.0. However, there are a number of plants that would prefer a pH lower than 6.5.
Another factor that is important is plant placement. Norm says "Consider the exposure to wind, such as hot, drying south winds, or cold, dessicating north winds. Both are equally important. For example, Birch trees growing in a south exposure, versus a north exposure. Birch prefer a cool moist well-drained soil without exposure to hot, drying conditions. There is a direct link to Birch trees thriving on the North or East sides of a home, if all other basic factors like soil pH, drainage, and proper selection of variety are met." Many other trees and shrubs have similar limitations.
Light intensity can also have an effect on plants in the landscape. Hosta, a popular perennial grown for its unique leaf color, is sometimes incorrectly planted in full sun, in a south or west exposure. This will result in burned foliage, or plant death. On the other hand, ornamental grasses planted in shade or partial shade will not perform to expectations in low-light conditions. As a general rule, the widest variety of plant materials will grow on an East exposure, or in open landscape beds on the east side with good air circulation. The most difficult exposure to grow plants is usually the southwest or west due to extreme heat, lack of moisture, wind and light intensity. The key to remember is a site where the soil has not been disturbed, or a "natural soil state" would have better results for a wider variety of plants. The detrimental effects of heat, cold and wind can be minimized by using organic mulches. The mulch, when applied correctly, will help even out the peaks and valleys.
Colin also offers this advice....."the most common mistake when planting a tree, shrub or perennial, is planting too deep. The planting depth should not be any deeper than it is in the container. When planting, however, the planting hole needs to be wider than the pot width. Lastly, firm the soil going back in the hole, then mulch correctly over the root ball and water as necessary." He also says, "Plants that are purchased in containers do not need to be fertilized immediately. Most nurseries will provide the plants with what they need for basic start-up growth. Also, most new landscape plants have a confined root system. Therefore, it is not recommended to use concentrated fertilizers or "spike" fertilizers."
"Other than removing broken branches, we do not recommend pruning at planting time." Norm explains "Every leaf on a new shrub or tree is making and storing energy for future root and shoot growth. Established trees, shrubs, perennials and evergreens, should not be pruned until late winter or early spring."
"Winter-burn on most Arborvitae, a commonly planted evergreen, can be directly attributed to late summer pruning because it stimulates new growth, and exposes tender new foliage to intense sunlight." If all or most of the above factors are met, the only other concern would be damage caused by external factors such as rabbits, mice, voles, and deer. Protection for trees must not be restrictive, and should be inspected or replaced annually to keep up with a trees growth. White colored tree guards are preferred over dark colored due to heat absorption. Most importantly, keep the weed-whip away from the base of trees. Once the outer layer of bark is damaged, the end is near.
Norm also urges homeowners to leave the cleanup and cutting back of their perennials until spring to avoid winter damage especially during open winters because the leaf material will protect the roots and crowns. Most shrubs can also be pruned in the spring, with some exceptions. "Why plan a landscape for maximum beauty, then prune the plants at the wrong time and remove all the flowers for the next season?" Norm asks.
Colin reminds homeowners "Plants in newly installed landscapes also need to be hydrated going into winter to insure survival. Assuming plants are mulched when planted; regular watering in the fall will help minimize moisture stress. Roots continue to grow until the ground freezes, which can sometimes happen as late as November."
For more information, contact your local plant professionals at Norm's Greenhouse and Nursery LLC, Aurora, South Dakota.
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