Wait for passed frost and warm soil
Direct sowing
After the last frost, in warmed soilOregon State uses at least 50°F soil for its direct-sow guidance.
Indoor start
Only a short lead timeIllinois Extension uses 2–3 weeks before outdoor planting and cautions that roots dislike disturbance.
There is no national calendar day
Illinois gives an early-to-mid-May example for its region, while Oregon State uses different local ranges. Follow your local frost and soil conditions instead of averaging those dates.
Choose the simpler method first
Sunflowers are fast-growing annuals that are usually easy to direct seed. Choose an indoor start only for an earlier display or when your outdoor season is short, and move seedlings gently before they become rootbound.
Plant for the variety you chose
Oregon State plants sunflower seeds about 1 inch deep. Spacing changes with the plant habit: branching plants need more room than single-stem varieties. Read the packet before deciding whether a row is for tall plants, cut flowers or a compact container type.
Use this quick planting plan
Direct sow
Use a sunny, well-drained bedKeep the soil moist until seedlings emerge, then thin according to the selected variety.
Start indoors
Do not start too earlyMove plants outside only after frost danger has passed and before roots fill the pot.
Longer display
Use successive sowings if your season allowsIllinois Extension notes that planting at intervals can extend bloom time.
Quick questions
Can I sow before the last frost?
NoWait for frost-safe conditions and warm soil.
Are transplants required?
NoDirect sowing is the straightforward default for sunflowers.