Soil Types & Soil Preparation
Soils are classified by the size of the most prevalent mineral component, and are generally described as sandy, clay or loam. Sand particles are relatively large and round, and fit together loosely; think of a bucket full of tennis balls. Clay particles are small and flat and pack tightly together; think of stacks of pancakes. Loam is comprised of a good balance of sand, clay and silt (silt is defined as particles of the earth that are somewhere in between sand and clay in size).
Sandy soil warms quickly in the spring, is light and easy to dig, drains quickly and contains a lot of oxygen. It doesn't retain water or nutrients so it dries out quickly and doesn't offer much in the way of plant nutrition. Unless you are growing plants that are adapted to sandy soil, plants grown in this kind of soil need frequent watering and fertilizing.
Clay soil retains moisture and nutrients, but is heavy and harder to dig than sandy soil. It warms slowly in the spring, drains slowly and contains little oxygen.
(Referred to as "Normal" in our Product Quick Facts Box)
Loam has a good balance of clay, sand, silt and organic matter particles. It drains well, but doesn't dry out too fast. It is rich in plant nutrients, is easy to dig and has plenty of air space.
What Type of Soil Do You Have?
To get a general idea of your soil type, take a handful of moist soil and squeeze it. Clay soil forms a tight ball that stays together when you tap it. Sandy soil doesn't form a ball and may run through your fingers. Loam holds together when you squeeze it but falls apart when you tap it.
For a detailed report on your soil, you can gather samples and have them tested by a soil testing laboratory. Many states offer this service through the county Cooperative Extension office. Go to http://www.csrees.usda.gov/Extension/index.html to find the office nearest you. There are also private labs that test soil. Test results will tell you the type of soil you have, the amount of organic matter it contains, the nutrient levels and pH. The report usually suggests materials to add to your soil to improve it based on what you want to grow.
The Ideal Soil
So just what is the ideal soil? For most of the plants we sell at Great Garden Plants, you want a well-drained, loamy, nutrient rich soil with 5 percent organic matter and a pH between 6.0 and 7.2.
Now that we know what the ideal soil is, how do you get it? Soil preparation is the answer. Keep in mind that perennials, trees, shrubs and vines are permanent residents in your landscape, so preparing the planting area is the best investment you can make to get your plants off to a good start.
For best results, plants must have good drainage, adequate nutrients and available water at all times. If you are creating a new garden bed, begin by removing grass and weeds. Start by "peeling away" about two inches of the surface, and "skimming" the grass off with a spade.
Spread 2-3 inches of organic matter such as peat moss, compost, or aged manure (up to 4 inches if the soil is very poor), over the planting area, and thoroughly dig in, or till to a minimum depth of 6-8 inches. This will improve drainage in heavy clay soil, and will help sandy soil hold moisture longer. Break up clods of dirt, and remove rocks. Rake the soil level, and remove any large clumps.
Because the pH range of approximately 6 to 7 promotes the most ready availability of plant nutrients, and can also influence plant growth by its effect on activity of beneficial microorganisms, knowing your soil pH is important. The most accurate method of determining soil pH is having samples tested by a lab. A second option, which is simple and easy, consists of using a PH meter, or using certain indicators, or dyes. Meters and soil dye test kits can be found in many stores that offer gardening supplies. Be sure to test the soil in different areas of your garden, and at different depths (top 3 inches, 6 inches, and 12 inches) as plant deterioration, manure, and microbial activity can affect PH levels.
If your soil test indicates your pH is too high or too low, add lime or sulphur to correct it. A pH below 6.0 means your soil is acidic, and may need to be adjusted with dolomitic limestone. If the pH is above 7.2, your soil is alkaline, and can be adjusted with iron sulfate. Refer to your soil test for recommendations on additional plant nutrients.
In established gardens, remember to add organic matter every time you add a new plant. It's also a good policy to add a 2 or 3 inch layer of organic matter on top of the soil in the fall. As the organic matter breaks down, it will improve soil structure, help maintain a PH balance, and feed plants.