Cultivate the soil to a depth of 12 to 16 inches. Crush large dirt clumps. If the soil clumps excessively, lay the clods on top of the soil for a day to dry them out completely.
Till 6 inches of coarse sand – also known as builder's sand – and 3 inches of compost into the soil. Do not use fine sand as it may turn the clay soil into a cement-hard mass.
Spread 8 inches of wood chips over the amended flower garden soil. Water the area to a depth of 20 inches.
Allow the wood chips to remain on the soil over fall and winter. Either till it into the soil in spring or leave it as a mulch for spring flowers.
Use a mattock or rototiller to break up the top 10 inches of soil.
Spread 1 inch of compost over the area and rototill it into the soil. Spread another inch and rototill again. Repeat the procedure with 1 more inch of compost.
Plant grasses or legumes, or both, in the flower garden. Rye, oats, crimson clover or hairy vetch work well.
Cut the cover crop to the soil in spring when you are ready to plant. Use pruning shears, loppers or a machete, depending upon how heavy the crop is. Rototill the plants and cuttings into the soil.
Repeat the process each fall.