What is Clay?
Clay is generally a thick, sticky soil made primarily of clay particles. There is generally a substantial amount of water trapped within the clay, which gives it its thick properties. Clay is formed by the degeneration of silicate-bearing rocks by small amounts of carbonic acid and other diluted solvents. High clay content gives clay soil properties, which make it difficult to work with. Soils that have high clay content generally are not welcoming to many annuals, perennials, and vegetables. Plants that require bulbs to grow tend to rot over the winter in the clay soils. Although many gardeners find this soil difficult and frustrating to work in, there are several options a gardener can implement to make the thick soil easier to work with and more fertile to various plant species.
Taking a sample of soil and having it analyzed is the best way to gather information about soil composition. Soils that contain more than 50% clay are considered ‘heavy clay’ soils. Soil testing provides information about the pH balance and nutrient balance of the soil. While clay is rich in nutrients because it attracts minerals such as potassium, calcium, and magnesium, it is difficult for plants to access the nutrients because of the structure of the soil.
Even if a soil test in not available, clay is still easy to identify. When clay is wet, it becomes sticky and clumpy. Clay generally tends to stick to hands, shoes, and gardening tools. When clay is dry, it forms cracks, and has a heavy, packed feeling when held. Because of their density, clays are also known as heavy soils. This density causes poor drainage, creating a build-up of water, which can be bad for most plants. Clay’s density causes compaction, adding to gardeners’ difficulty, along with the high alkaline measurements. While most trees and shrubs can handle clay’s conditions, many small plants and bulbs cannot.
There are a few options for gardeners faced with clay soils. One option is to plant apt trees and shrubs. Another option is to add soil amendments to improve the condition of the soil. If a gardener chooses to improve the condition of the soil, it is best to improve an entire area at once, rather than small patches or planting holes, at a time. The problem with amending small patches or planting holes is that as plants grow, they send out roots, and eventually those roots will run into the clay soil. Soil amendments make the soil more susceptible to planting a wider variety of plants. Compost, manure, leaf clippings, and other organic materials can be added to the clay soil to amend the soil. Wet soil causes compaction, so working with dry soil is best. If the clay soil has a high alkaline level, gypsum may be added to balance the soil.
It is up to the individual gardener as to what to do with clay soil. It is important to note that soil amendments can take several years to take effect. While adding organic materials encourages the growth of microorganisms that improve the condition of the soil, it takes some time for most microorganisms to work through the soil.