Do sunflowers need special fertilizer?
Written by
Julia Anderson
Reviewed by
Prof. Charles Hartman, Ph.D.Despite their large size, sunflowers do not require a lot of fertilizer. Use a little balanced 10-10-10 fertilizer when planting. Too much fertilizer will result in an abundance of stems and leaves, but few flower heads. I apply soil amendments to the soil whenever possible, rather than using chemical fertilizers. Healthy sunflowers typically don't require additional feeding after they have established and received the initial nutrients.
Soil Preparation
- Mix 2-3 inches of compost into soil before planting
- Avoid fresh manure that burns roots
- Test soil pH (ideal 6.0-7.5) before adding amendments
- Use organic matter to improve nutrient retention
Fertilizer Timing
- Apply once at planting for most varieties
- Reapply only if leaves yellow during growth
- Never fertilize after bud formation begins
- Stop feeding 6 weeks before expected frost
Problem Solving
- Yellow leaves indicate nitrogen deficiency
- Purple stems signal phosphorus need
- Curled leaves suggest potassium shortage
- Always water thoroughly after fertilizing
Be vigilant for signs of over-fertilizing. Brown edges on the leaves evidence leaf burn. Soft and spindly growth indicates too much nitrogen input. A salt crust will appear on the surface of the soil, indicating a mineral buildup. If you detect one of these signs, immediately flush the soil with water.
Effectively apply low-input feeding strategies. Instead of chemical fertilizers, apply compost tea as a top dressing every four weeks. Use chopped comfrey leaves as a substitute for nutrient-dense mulch, and consider planting legumes nearby to fix nitrogen. Each of these contributes to a more gentle form of nutrition with no risk of burning the plants.
Modify practices according to sunflower types. Giant mammoth types respond to increased phosphorus during bud initiation. Dwarf container types should be fed once a month with half liquid fertilizer, and pollenless cut-flower types with the longest vase life require little feeding. Always match nutrition to growth type.
Read the full article: When to Plant Sunflowers: Full Guide
