How to Increase Flower Bed Fertility

Test the soil following the instructions in a soil testing kit. The test results indicate the soil pH and basic fertility requirements of the bed. Soil pH adjustments take up to nine months to occur, so test and amend the soil the summer or fall before the spring you intend to plant.

Sprinkle powdered limestone over the surface of the bed. Use the amount indicated as necessary by the test to bring the soil pH into a range of 5.5 to 7.0. Most flowers need a pH near 6.3.

Turn the limestone into the top 8 inches of soil. Use a power tiller, hoe or a spade to incorporate the limestone with the soil.

Cover the bed with a 2- to 4-inch layer of compost immediately before planting. Till the compost into the top 6 inches of soil. Use 1 inch of compost in the spring over perennial beds that already contain flowers.

Fertilize the bed with the type and amount of fertilizer recommended by the test results, or with 3 pounds of 8-32-16 slow release fertilizer per 100 square feet of bed. Work the fertilizer into the soil prior to planting annual flowers. Sprinkle the fertilizer on top of the soil 6 inches away from the plant stems in perennial beds. Water the bed after the fertilizer application so it soaks into the soil.