Clay soil has the finest texture of all the soil types, with particles of rock so fine they are actually dust. Clay soils are notoriously difficult to garden in, as its fine texture turns to a heavy, sticky mass when wet. This reaction makes clay soil very slow to drain and plants often become waterlogged when their roots sit in consistently soggy soil for extended periods of time. While some trees and shrubs are adapted to clay soil, most gardeners choose to add soil amendments to clay soil to lighten its texture and improve drainage.
Grab a marble-sized piece of soil and hold it in your hand.
Mist the piece of soil with a water bottle until it is moist.
Knead the piece of soil in your hand until it is the consistency of putty.
Squeeze the piece of soil between your forefinger and thumb. Push and roll the soil with your thumb until it forms a ribbon shape.
Look at the ribbon of soil. If it forms a solid ribbon and sticks together that indicates clay soil.
Note the texture of the soil. If it feels sticky in your hand and the surface is slick and smooth, with no grainy texture, it is clay soil.
Place 2 inches of soil into a 1 liter jar. Pour water into the jar until the jar is 2/3 full.
Add 1 tsp. of table salt to the jar. Place the lid on the jar and shake the contents vigorously to mix.
Place the sealed jar on a counter where it can remain, undisturbed, for several days.
Measure the bottom layer of sand after one minute. Wait two hours and measure the layer of silt that sits on top of the sand layer.
Measure the clay layer after the jar has sat, undisturbed, for several days. If the clay layer is the largest layer the soil is considered clay soil.