The Soils Best for Growing Sunflower Seeds

Soil Quality

• Sunflowers need well-drained soils that are rich in organic matter. The plants can't tolerate wet soils, so avoid beds with heavy clay content or areas where water pools on the soil surface after rainfall. Working compost or peat into the bed before you plant the sunflower seeds helps improve drainage and adds organic matter. In areas with poor soil, planting in a raised bed or a container allows you to use a better quality, well-draining potting soil.

Temperature

• The seeds won't germinate in cold soils. Seedlings transplanted to a cool soil bed grow poorly and may die. Sunflowers require soil temperatures above 65 degrees Fahrenheit to germinate and grow well. Waiting until a week or two after the last spring frost date usually gives the soil enough time to warm sufficiently. The soil in raised beds typically warms more quickly than that in standard garden beds. Laying black plastic over the bed in the weeks before planting may also help warm the soil more quickly.

Fertilization

• Amending the soil with compost usually provides sufficient nutrition for the sunflower plants. Container-grown plants require twice monthly fertilization with a soluble balanced plant food since nutrients are naturally present in the potting soil. Garden sunflowers also benefit from a preplanting addition of a slow-release fertilizer. If the plants grow slowly or seem weak, a midseason application of fertilizer helps encourage lusher growth. Top dressing the bed with an inch of compost at midseason also provides some nutrients to the soil.

Moisture

• The high sun requirements of sunflowers cause soils to dry out more quickly due to evaporation. Adding compost to the soil before you plant prevents sandy beds from drying as quickly, but the plants still need one to two weekly waterings so that the bed remains moist. The soil in containers and raised beds dries out more quickly than regular beds, so these types of plantings may require daily watering during dry periods so that the soil remains moist.