Plants thrive most when the soil where you plant them is loose, friable and easily manipulated. Roots need space to stretch out and feed off nutrients and minerals that are naturally occurring in native ground. In certain areas, native soil may be higher in hard packed clay, which is dense and hard for tender roots and shoots to penetrate. To assist the roots in having the best chance possible, amend clay soil with organic matter to improve its texture.
Dig into the native soil where you intend to plant. Break the ground with a tiller or shovel and work the clay soil until you reach a depth of at least 6 inches. Some gardeners double-dig, which is breaking the soil up to a depth of 1 foot.
Take a soil sample to your local agricultural extension office for testing. The staffers will analyze the soil and recommend what amendments you may need to bring the soil's nutrients and minerals to optimum levels.
Procure any elements recommended by the extension office as well as organic matter such as compost, humus, peat moss, processed cow or zoo animal manure, topsoil and mulch, or a mix of those ingredients known as planter's mix. You can purchase these supplies from the local garden center or mulch yards
Dump the organic matter and ingredients recommended by the agricultural extension on top of the broken up garden soil. Mix in thoroughly with the tiller or a shovel and hoe. Mix the entire depth and width of the dig site with the amended soil.
Smooth out the new planting area with the hoe. The texture should be a rich dark brown, loose friable soil that is soft enough to dig into with a gloved hand. Once this is accomplished, your clay garden soil is amended adequately and ready to receive plantings.