> Next: Sun, Shade, and Wind
Site, Sun, and Exposure
Considerations
Climate, Microclimates, and Site Conditions
Because they help predict which trees and shrubs will survive in typical home landscapes, gardeners often pay much attention to the U.S.D.A. Plant Hardiness Zones [see: Plant Hardiness and Climate].
While important considerations for choosing plants, the zone maps provide information for broad regions, rather than useful specifics you can apply to an individual garden.
Experienced gardeners use the zones as a guide, but also consider so-called “microclimates.” The variation between areas of a region—even neighborhoods and yards across the street—change where and when to plant and grow trees and shrubs in each yards.
Note the three homes shown in the diagram that follows. All are within a few miles of each other, but gardening is very different for each homeowner.
Read on to learn about the variables that create microclimates and learn how to recognize them in your own yard.
Sun and Shade
Make sure your trees and shrubs have the conditions they need to thrive in your yard. Check its sun and wind exposure along with its soil quality.
Your trees and shrubs are usually the most significant part of your total landscape investment.
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When it comes time to plant, you’ll put your directional knowledge to good use. Certain plantings of trees and shrubs will flourish in sunny exposures. Others prefer cooler temperatures and shadier spots. Start by locating your garden to the sunlight it receives.
If you have a compass, you can easily note North, South, East, and West. Carefully note where the sun rises and sets.
In the northern hemisphere, the summer sun rises in the northeast, traverses a high arc, and sets in the northwest. During winter, the sun rises in the southeast, crosses lower in the southern sky, and sets in the southwest.
(Southern-hemisphere gardeners follow similar seasonal patterns. Below the equator the sun’s travels closer to and farther away from the south, rather than the north. Southern winter is the north’s summer, and visa versa.)
Observation will also reveal how much summer shade and winter shade differ. Winter shadows are longer, cover more area, and change more quickly.
For instance, a fence that is 8 feet (2.4 m) tall might cast a shadow at noon in the summer of 2 feet (60 cm). The same fence throws a shadow 12-feet (3.7-m) long in midwinter. These differences are things to keep in mind when planting trees and shrubs near shading structures.
Also take time outside to see the type and quality of sun and shade your site receives.
Full sun is usually defined as a minimum of 6 hours of direct sunlight per day. Full shade means an area gets less than 2 hours of direct sun per day. Areas that receive 2–5 hours of direct sun are said to be either partial shade or partial sun locations.
Sites located under a shading tree’s foliage are said to be areas of filtered sun or filtered shade.
Soil and Moisture
Next, look down and inspect your yard’s soil. Dig down in several areas of your site and examine the soil to determine if it is clay, sand, or loam. Collect a soil sample if you wish to have it tested to learn the soil’s specific fertility and acid-alkaline balance [See: How to Test Soil Texture and Richness, on this page].
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Also note the moisture levels of your soil by digging down several inches and feeling for dampness; repeat this over a period of time.
This is worthwhile even if you live in an especially arid region or in an area known for frequent rains. You may have to apply moisture or tarp an area to see how much water it absorbs for a week or more.
Moisture levels in soil vary because of soil type, sun exposure, drainage issues, and other factors. There probably will be some differences within your site, regardless of its size or location.
Wind Exposure
More than heat, winds rob moisture from trees and shrubs. Drying winds force them to increase their natural rate of transpiration, or evaporation of water carried from their roots to their foliage.
Young plantings are more susceptible to wind than mature trees and shrubs. Where possible, mark out planting spots for wind-susceptible plantings. Shelter them from winds. As another option, pick and plant only wind-tolerant species in such exposed locations.
About Your Site
How to Test Soil Texture and Richness
Judging the quality of your site’s soils means understanding their structure and the nutrients they contain.
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Soils are typically dense (clayey, with slow drainage), loose (sandy, with very fast drainage), or well-structured (a mix of decayed organic material, water, air, and roughly equal amounts of sand, silt and clay that holds and releases water as plants need it).
The richness of soil depends on how much of the main nutrients—Nitrogen (N), Phosphorous (P) and Potassium (K)—it contains, along with minor and trace nutrients and minerals.
Laboratory testing is an easy way to determine your soil’s nutritional richness and acid-alkaline balance, or pH. Local university agricultural extensions, Master Gardeners, and most major garden retailers can help you arrange expert testing of your soils, but here are the steps for collecting and preparing soil test samples.
Collecting and Preparing Soil Samples
Dig a hole 12 in. (30 cm) wide and deep. Using a clean trowel and plastic cup, scrape a cup (235 ml) of soil from the side of the hole, 6–8 in. (15–20 cm) from the surface. To get a representative sample, repeat in different areas of your planting area and thoroughly mix each sample of soil together.
Gauge soil structure by scraping a second soil sample into your hand and clenching it in your fist into a ball. When you open your hand, proper soil with good texture should crumble loosely. Wet, sticky soil contains too much clay; a ball that completely falls apart indicates a too-sandy soil. Both require additives and amendments to improve their texture.
For testing at a soil testing laboratory, pour the soil sample into a clean, sealable plastic bag. Close the bag and label it with your name, address, and the date of collection.
Wrap and mail the soil sample to the soil testing laboratory. The names and locations of soil testing laboratories may be obtained from garden retailers and from U.S.D.A. and Agriculture Canada agricultural extension offices.
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