Sunflowers (Helianthus)
Native to North America, sunflowers grow wild in many areas of the U.S. They have a long history of economic importance, though their original cultivation timeline is uncertain.
Temperature
Sunflowers are tolerant of both low and high temperatures. Germination starts at 39°F, but 46–50°F is ideal. Seedlings can survive to 23°F in early stages. Mature plants are damaged below 28°F. Optimal growth is 70–78°F, though 64–91°F is still productive. High heat can reduce oil content, seed fill, and germination quality.
Soil
Sunflowers grow best in well-drained soils with high water-holding capacity and a pH of 6.5–7.5. Moist seedbeds promote even germination. While sunflowers tolerate various soil stresses, performance is best under well-managed, neutral soils.
Planting
In northern areas, plant between May 1 and late June. Early maturing hybrids are ideal for late planting or replanting. You can plant sunflowers two weeks before the last frost and up to 100 days before the first fall frost.
Spacing
Sunflowers thrive across a range of row widths and populations. Solid seeding (under 20" row spacing) or traditional row spacing (30–36") are both successful. A depth of 1–3.5" ensures proper moisture contact. For crust-prone soils, shallower planting is advised. Narrow rows benefit semi-dwarf varieties at high populations.
Harvest
Sunflowers mature 30–45 days after bloom when the back of the head turns yellow and bracts brown. Seed moisture is around 35% at physiological maturity. Wait for seed moisture to drop below 12% for temporary storage or 10% for long-term. Seeds with up to 15% moisture can be temporarily stored during freezing weather. Early harvest minimizes weather risk but may require mechanical drying.
Use commercial headers with pans and a three-armed reel to reduce seed loss during direct combining. Narrow pans (9") work well for diagonal harvest passes.
For more information, please see links below:
- North Dakota State University - Sunflower Guide
- Texas A&M - Sunflower Production
- University of Tennessee - Sunflower Guide
Note: This information is summarized. Additional details and expanded guidelines can be found in our production sheets available in the Holmes Seed Grower's Guidebook.
Downloadable Copy: