University of Illinois Extension
Soil Preparation - Gardening with Annuals - University of Illinois Extension

Soil Preparation

No matter how well you plan or how good the quality of the plants are, you will not succeed without a good foundation and a good home for roots: a well-prepared soil. Prior to planting, it is necessary to prepare the soil, especially if a flower bed has never been in that location before. After laying out the area and determining what the flower bed will look like, remove all grass and weeds prior to tilling the soil. An alternative to sod removal is to apply the herbicide glyphosate to the area. It will kill off existing vegetation. After the vegetation is dead, it can then be tilled into the soil. Read and follow label directions carefully to avoid misuse.

soil sample in hand

All gardens benefit from the incorporation of organic matter to help improve soil texture, tilth, aeration and drainage. Apply materials such as peat, compost, leaves, grass clippings, and manure. This will mean adding approximately 3-4 inches of organic matter tilled into the top 6-8 inches of soil. The area should also be fertilized using a general-purpose fertilizer such as 5-10-5, 10-10-10, 12-12-12 or similar analysis at a rate of 1-1/2 to 2 pounds per 100 sq. ft. of garden bed. After thoroughly working all of the material into the bed, rake the area level and you are ready to plant.

Most annuals will grow very well in soils with a pH between 6.5-7.5. Because most of our soils in Illinois fall within this range there should be no cause for drastic pH adjustments. If improper pH is a concern, then you should have your soil analyzed by a certified soil testing lab. Many labs perform this service. After results are received, an informed decision can be made as to the best course of action. Before blaming fertility or pH problems for poor annual performance, be sure you have spent adequate time in soil preparation. That is the key to quality plant growth.

Always work soils that are of the proper moisture content. Working soils too soon in the spring when they are still wet will result in damage to the soil structure. These soils become very hard, poorly drained and poorly aerated. Test before you dig by taking some soil and squeezing it into a ball in your hand. Touch the ball. If it crumbles readily the soil is safe to work. If it remains in a tight ball, it is too wet and you should not work it until it has a chance to dry out further.