Growing Guide

Sunflowers are cultivated from seeds planted directly in the garden after the last frost.

Plant seeds in average soil under full sun once the risk of frost has passed. When selecting a site, ensure the soil drains well as sunflowers thrive in open, sunny areas. Taller varieties should be planted at the northern end of your garden to prevent shading other plants. Prepare the soil by clearing weeds and incorporating organic matter into the top 6-8 inches, then level and smooth the surface. Most plants benefit from soil enriched with organic matter. Compost, rich in nutrients with an ideal pH, can be added at any time. If compost isn’t available, apply 1-2 inches of organic mulch after planting, which will decompose into compost over time. After the growing season, conduct a soil test to determine necessary amendments for the following year. Plant seeds ½ inch deep in groups of 2 or 3, spacing them 18-24 inches apart depending on the variety. Gently firm the soil, water thoroughly, and maintain even moisture. Seedlings typically emerge in 7-10 days. Once seedlings have two sets of leaves, thin them to one plant per group. Control weeds throughout the growing season as they compete with sunflowers for water, space, and nutrients. Regular cultivation or mulching can prevent weed seeds from germinating. Mulching helps retain soil moisture and keeps soil temperatures consistent. For annuals, shredded leaf mulch provides a natural appearance and enhances soil quality as it decomposes. Always keep mulch away from plant stems to prevent potential rot. Keep soil consistently moist but avoid overwatering. Established sunflowers can tolerate drought conditions. Avoid fertilizing unless soil quality is poor; over-fertilization should be avoided. Monitor plants for pests and diseases. Consult your local Cooperative Extension Service for recommended pest control methods in your area. Some sunflower varieties produce only one bloom, after which the plant can be removed. Remove plants after frost kills them in the fall to prevent disease issues the following year. Edible sunflowers mature approximately 3 months after sowing. Harvest seeds by cutting heads when stalks are dry but before fall or winter rains. Check heads for maturity—center florets should shrink, the back of the head should yellow, or the head may begin to droop. Hang heads in a warm, dry, well-ventilated area to allow seeds to ripen fully. Use cheesecloth, netting, or a paper bag with ventilation holes to protect and collect seeds as they dry. Shorter sunflower varieties are suitable for container gardening; use a commercial potting mix. Pollen-free varieties make excellent cut flowers.