The Soil Factor
Before you bring home the proper trees, shrubs, or vines for your yard, you must analyze the soil, water, and drainage conditions in your yard. You then must determine whether any changes should be made. It is always easier to do this before you begin planting. It's also less costly: You won't find yourself having to replace dead or dying plants.
The soil your plants grow in serves many purposes.
Be sure to analyze your soil before purchasing any plant.
Some soils, however, may be extremely dense, with little air space between the particles. This type of soil, called clay, is made up of particles of rock so tiny and close together they allow little air circulation. Clay holds water well, sometimes perhaps too well. Sandy soil, on the other hand, contains larger particles of rock. Air is present in abundance in sandy soils, but water runs straight through. This creates dry growing conditions, even in a moist climate.
To determine which type of soil you have, squeeze some slightly moist soil in your hand. Clay soils will form a compact lump and retain their shape. Loam soils will form a ball but fall apart if poked at. Sandy soils won't hold their shape at all.
Both sandy and clay soils can be improved in the same way: by adding organic amendments. Add about one-third compost, well-rotted manure, or other organic matter, and mix carefully. Clay soils also require the addition of sand to open up air spaces. Use coarse sand in combination with organic matter, and incorporate both amendments thoroughly. Use of sand alone will do little to open a clay soil-and may make the situation worse. If possible, do this for the entire lot or at least the entire planting area. You don't want to create a single pocket of good soil surrounded by poor soil because your plant, as it grows, will want to send its roots further afield, beyond the original planting site.
Roots may be hesitant to leave the pocket of good soil to penetrate the surrounding inhospitable soil. It is also worthwhile before planting to test your soil's pH level. This is a measure of acidity and alkalinity. The pH scale runs from 1 to 14, with 7 being neutral. Anything above 7 is increasingly alkaline, anything below, increasingly acid. Most soils in North America fall in a pH range of 6 to 7, from slightly acid to neutral. This is ideal for most plants.
Garden centers and local Cooperative Extension offices usually offer an analysis service and will explain how to collect a soil sample. You can also buy a pH kit and do your own testing, but the results will be less specific than with a professional test.
If your soil is on the alkaline side (7 or above), consider either planting plants that tolerate alkaline soils or amending it with peat moss or sulfur. If your soil is very acid (below 5.5), try either planting acid-loving plants or adding ground limestone. The exact quantities of amendment needed to change your soil's pH to the one you want depends on a great many factors, notably its original pH and the type of amendment used. A professional soil analysis will indicate the exact amount.
Water makes up about 90 percent of the tissue in leafy plants. Woody plants have an advantage over perennial ones in that they generally have extensive root systems that reach down and out for great distances, often far beyond the circumference of the plant's branches. Thus, woody plants can seek out moisture and continue to grow even as other plants suffer from lack of water. But there are limits to this ability. Most woody plants prefer soils that are evenly moist, meaning soils that may dry out on the surface but remain slightly moist underground.
If your area is subject to regular or prolonged droughts, you should consider planting trees, shrubs, and vines that are naturally drought-tolerant. But even drought-tolerant plants don't appreciate extreme drought. You might want to consider installing an irrigation system to facilitate watering. Newly planted trees and shrubs will need extra care in watering since their root systems are quite limited, especially during the first year.
Some soils suffer from chronically poor drainage. They are spongy and moist at all times and may even be inundated for days on end. There are some woody plants that thrive in soggy soils, such as river birch, (Betula nigra) and sweetbay magnolia (Magnolia virginiana). To expand your choices, it will be necessary to improve the drainage of your yard before you begin to plant.
There are three levels of soil: the top and the
bottom are porous soil. The middle is hardpan soil.
Dig through these layers for planting.
If your garden is underlaid with hardpan, a nearly impervious layer of clay about a foot beneath the soil's surface (a common problem in dry climates), you can solve the problem by breaking through the hardpan in several places and filling the resulting holes with porous soil. In many cases, however, the best solution for poorly drained soils is to install drainage tiles. You can also consider planting woody plants in raised beds or mounds to give them a few extra feet of soil in which to grow. This will provide enough well-draining soil for good air circulation, and the moister soil beneath will ensure that roots never lack water.
Sun, Shade, & Wind
Each plant in the wild fits perfectly into its own niche. Some trees rise high into the air, basking in the sun while being pummeled by harsh, drying winds, and they thrive under such conditions. At the feet of these tall trees, small trees and shrubs live in a different environment: no harsh wind and no brilliant sun. These plants trade abundant solar energy for protection from the elements.
The same pattern is repeated in your yard. Some parts are shady much of the day, others are sunny. Some parts are exposed to dominant winds, others are protected. These elements are in constant flux. As trees and shrubs grow, they modify the environment around them, creating more shade and a greater barrier against the wind.
Plants gather energy from sunlight. It would seem reasonable that most plants should grow faster and denser with full sun. But with nearby walls, fences, and trees, full sun is rare in the average backyard. Most "full sun" plants actually grow well enough with fewer than 12 hours of intense sunlight per day.
Most woody plants grow almost equally well in full sun or partial shade. Full sun tends to stimulate increased flowering and helps bring out more brilliant fall colors. Some protection from hot afternoon sun is good for even "full sun" plants.
In general, deciduous flowering shrubs and trees need the most light, broad-leaf evergreens the least. Silver- or gray-leaved plants are also avid sun lovers. Variegated plants generally prefer bright shade (ample light with little direct sun); they can burn in full sun. Most conifers grow best in partial shade to full sun, although a few, such as yews, do well in shady conditions as well. Most shade plants require some sunlight.
The best shade for most plants is dappled shade, which is sunlight piercing through the leaves of tall trees. Such shade provides good light all day while keeping out the burning effects of full sun. The least hospitable shade is that found to the north (to the south in the Southern Hemisphere) of walls and other structures with much dense vegetation nearby. The shade cast by dense conifers is also a challenge. In such places, sunlight can be cut out entirely, allowing only reflected light to reach the plants. Even so, there are trees, shrubs, and vines that will grow there.
Of all the exposures, an eastern one provides the most sun with the least burning rays. It offers bright morning sun for several hours per day, but it never becomes too hot. Western exposures offer a similar number of hours of sun, but the site will be much hotter. Southern exposures offer full sun for six hours or more a day, but the intense heat can be harmful to many plants. Northern exposures are the coolest of all, which is a major plus on hot summer days, but receive little direct sun. They are best reserved for foliage plants.
Mature conifers and broad-leaf evergreens create the deepest shade. They cut off sunlight for the entire year.
In sites with severe wind, a row of wind-resistant trees or shrubs,
known as a windbreak, may be needed for plants to thrive.
Strong winds can do severe damage to plants, especially during the winter months. As the wind blows through the leaves and buds, it dries the air, causing leaves to burn on the edges and flower buds to abort. The windier it is, the more damage cold temperatures will do: This is the "windchill factor" so well known to those who live in cold climates. Plants that are borderline hardy in a given zone should always be planted where they won't be affected by strong winds. The best protection from strong winds is offered by other plants. They buffer the wind rather than cut it off entirely.
Conifers and wind-resistant broad-leaf evergreens are the best choices for softening wind year-round, although even the leafless branches of deciduous trees are surprisingly efficient at buffering strong winds. Fencing can also help buffer winds.
You know what tree you want, and you know where to place it in your yard. Now, it's just a matter of digging a hole and placing it into the ground, right? Well, not exactly. We'll show you how to plant a tree in the next section.