Clay soils retain moisture and are nutrient rich, but clay also drains slowly and compacts, making it difficult for most plants to thrive. Some trees and shrubs thrive in clay soil, but most annuals, perennials and vegetables struggle to establish their root systems. The National Gardening Association recommends adding organic matter such as compost to these soils to improve drainage and lighten the soil. Soil that contains bulbs will need to be treated differently to prevent damaging the bulbs. Amend clay soil containing bulbs in the summer when the plants have died. Amending the soil will produce a rich soil that any plant will thrive in.
Dig with a shovel 1 inch from each bulb in a circular motion until the bulb is completely exposed. Slide the shovel under the bulb and lift it from the soil. Place spring bulbs in a cool location until the soil amendments are finished. Place summer bulbs in a dry place for the winter.
Till the soil with a rototiller or rake 6 to 8 inches deep, working into the soil until it's broken into a workable consistency.
Remove weeds and rocks from the soil by sorting through it by hand.
Perform a soil test, available at gardening centers, to determine pH. Take samples from different areas of a dry garden, mix together and test.
Till amendments into soil, adding lime if pH is too low or sulfur if the pH is too high. Work to a depth of 6 to 8 inches. Add lime or sulfur until the desired pH levels are reached.
Till 2 to 3 inches of compost or manure into the top of the soil.
Rake the garden area level, smoothing the soil by dragging a rake back and forth across the soil until it appears even.
Water the soil well until it appears saturated.
Replant spring bulbs after amending the soil, following spacing requirements for each variety. Replant summer bulbs in the spring after any chance of frost has passed.