When to plant sunflowers

Sunflowers goes in by the calendar of your frost dates. Type your town to see the dates for your weather station.

The seed packet, in short

Sunflowers planting dates by zone

Each row uses the typical frost dates of a zone: the middle value among towns of 10,000 people or more in it. In zone 6b, for example, the typical last frost is Apr 20, so the first step for sunflowers, plant seed, falls Apr 20 to May 11. Towns in one zone can differ by two weeks, so your own town's dates above are the better guide.

Good to know about sunflowers

• Sow directly where they will grow once the frost danger has passed and soil has warmed to at least 50 F (60 F gives faster, better germination).
• Single-stem cutting types can be grown 4 to 6 inches apart; branching and giant types need 18 to 24 inches.
• Sow small batches every 2 weeks or so for a longer bloom season.
• Plant a little deeper (up to 2 inches) in sandy soil.

How to plant sunflowers

• Grow in full sun, ideally 6 to 8 hours of direct light a day.
• Use well-drained soil with a pH of roughly 6.0 to 7.5, and avoid low spots where water stands.
• Before sowing, work compost or other organic matter into the bed.
• A balanced fertilizer is enough; base the amount on a soil test when you can.
• Very tall plants can blow over in wind and may need a stake as heads get heavy.

Types that change the timing

• Single-stem types give one large bloom per plant; branching types give many smaller blooms over a longer stretch.
• Pollenless types are bred for cut flowers; pollen-bearing types are the ones to grow for bees and for seed.
• Giant types can pass 10 feet tall, while dwarf types stay about 2 to 3 feet and suit small beds and pots.

Common mistakes

• Letting weeds crowd young seedlings; keep the bed weeded early on.
• Leaving ripening seed heads unprotected; birds and squirrels can strip them, so net or cover heads before seed matures.
• Sowing in a soggy or compacted spot, which slows growth and makes plants more likely to topple.

Warm and cold regions

• Zones 3-6: Sow outdoors once frost danger is past, often late May or June in the coldest areas.
• Zones 7-8: Sow from about April into May after the last frost; repeat sowings keep blooms coming.
• Zones 9-10: Sowing can start as early as March where the last frost is early.

When it blooms

Flowers from midsummer into early fall; days to maturity vary widely by variety, roughly 45 to 95 days in one trial list.