Sunflower Seeds - Heirloom Mammoth Grey Stripe - Helianthus annus

2, 3, 4, 5, 6, 7, 8, 9, 10, 11

USDA Zones 2-11 - Grows as a warm-season annual across all zones. The planting time is adjusted based on local frost dates and soil temperature. Sunflowers are very adaptable and can be grown almost anywhere as long as they get enough sun and warmth.

Best performance across all zones with at least 80 frost-free days. The long, warm summers provide ideal growing conditions for maximum head and seed production.

Northern Zones (2-6) - Direct sow seeds after all danger of frost has passed. For an earlier start in areas with short summers, you can start seeds indoors 2-3 weeks before the last frost.

Hot Climate Zones (9-11) - Plant in early spring for summer harvest, or in late summer for a fall display. They handle extreme heat well as long as they have consistent water.

Soil Temperature - Requires warm soil for successful germination. A minimum of 60F is needed, with optimal soil temperature of 65-75F ensuring quick sprouting and strong plant establishment.

Growing Season - Requires 80-120 frost-free days to reach full maturity and produce a harvestable seed head. This makes it suitable for all zones when planted at the appropriate time relative to local frost dates.

Learn more about USDA Hardiness Zones here

When to Plant:

Direct Sow Outdoors: Sunflowers have a long taproot and do not like to be transplanted. The best method is to sow seeds directly in the garden after the last frost date, once the soil temperature is consistently above 60F.

Indoors: Only start indoors if you have a very short growing season. Use a biodegradable pot (like a peat pot) to minimize root disturbance when transplanting. Plant seeds 2-3 weeks before the last frost.

Planting:

Choose a Location: Select a spot in your garden that receives full sun (at least 6-8 hours a day). Sunflowers need full sun to grow tall and strong and to produce large flower heads.

Soil Prep: Sunflowers are not picky about soil type but prefer well-draining soil. They are heavy feeders, so amending the soil with some compost before planting will give them a great start.

Sow Seeds: Plant seeds about 1 inch deep. Space them 12-18 inches apart for Mammoth Grey Stripe to give them plenty of room to grow. You can plant them closer together if you are creating a "living fence" but the plants will be smaller.

Water: Water thoroughly after planting. Keep the soil consistently moist until the seedlings are established. Germination typically occurs in 7-14 days.

Care & Maintenance:

Watering: Water regularly and deeply, especially during dry periods. While they are drought-tolerant once established, a lack of water will affect their growth and the size of the seed head.

Fertilizing: A light feeding with a balanced fertilizer when the plants are about 1-2 feet tall can be beneficial. Avoid high-nitrogen fertilizers, which can produce weak stems.

Staking: Due to their massive height and heavy heads, tall sunflowers may require staking to prevent them from toppling over in strong winds.

Harvesting: The seed head is ready for harvest when the back of the flower turns from green to yellow-brown, and the seeds appear plump and are ready to fall out. You can cut the head off and let it dry in a protected area or cover it with a paper bag to prevent birds from eating the seeds.