Many gardeners are stuck with clay soils that are hard to cultivate, and in which many plants don't grow. How do you know if your soil is clay? How can you improve clay soils? What plants grow best in clay?
If your soil dries like a brick with cracks when it's dry, or in clods, and is like putty when wet sticking to shoes and tools, you have clay soil. It is hard for most roots to penetrate such soil. Take some soil, add a little water, and form a ball in your hand. Then squeeze the ball into a flat ribbon. If the ribbon reaches two inches long or more before breaking, this is a sign you have clay soil.
Soil particles come in different sizes, which contribute to soil texture. Sand particles are the largest, clay particles the smallest. Being so small, clay particles pack together not allowing the necessary spaces between them for air and water to flow, especially air that most roots need to function. Contributing to this is the fact that clay particles are plate-like, stacked like a deck of playing cards, with little space between them. This traps water for long periods. One positive side to clay is that its particles hold onto nutrients, making them more fertile.
So how do you increase the space between these particles? Some recommend adding sand, but unless it is coarse sand, and you add about 3 parts to each part clay soil, the soil structure will likely just get worse. When planting, some recommend putting gravel in the bottom of the planting hole. This is bad as it just raises the water level, creating what is termed a "perched water table". Another recommendation is to add gypsum, similar to lime, but this may increase calcium and pH levels too high (clay soils tend to be alkaline).