Sunflower
Common Sunflower, Giant Sunflower, Dwarf Sunflower, Helianthus, Annual Sunflower
Direct sow after last frost in full sun — transplanting disturbs the taproot. Excellent windbreak and shade provider for heat-sensitive crops. Attracts pollinators and beneficial insects. Harvest seeds when backs of heads turn yellow-brown and seeds are plump. To dry, cut heads with 12" stem and hang upside down in a dry, ventilated space. Cover drying heads with paper bags to protect from birds.
- Germination
- 7–10 days
- Soil temperature
- 18–24 °C
- Harvest after sowing
- 60–90 days
- Spacing
- 45–90 cm
When to plant sunflower
Sow outdoors from your last spring frost to 3 weeks after it.
Dashed line: typical last spring frost in zone 7 (Apr 5). Zone dates are averages; most of the UK is zone 8–9, central Europe 6–7 and the Baltics and Scandinavia 4–6. In the app, Tomatograph uses your garden's own frost dates.
How to grow sunflower
- 1
Sow direct
Sow 2.5 cm deep and 15–30 cm apart after the last frost, in full sun. Sunflowers have a taproot and dislike transplanting.
- 2
Water while young
Keep seedlings watered; established plants are drought-tolerant. Stake tall varieties in exposed spots.
- 3
Use the height
Tall sunflowers make a windbreak and shade for heat-sensitive crops, and attract pollinators.
- 4
Harvest seeds
When the back of the head turns yellow-brown, 60–90 days after sowing, cut it with 30 cm of stem and hang upside down to dry. A paper bag over the head keeps birds off.
Growing conditions
Light
Full sun
Water
Low water
Temperature
8–38 °C
Frost tolerance
Frost-sensitive — protect below 0 °C
Days to maturity
60–100 days
Ideal soil pH
5.5–7.8
How Tomatograph watches your sunflower
Tomatograph checks your local forecast every morning and only speaks up when one of these applies to your garden.
- Forecast of 2 °C or lowerFrost alert the evening before: cover plants with fleece or bring pots inside.
- 3 days at 35 °C or aboveHeat-wave alert while plants are flowering or fruiting: shade and water early.
- Humidity above 80% for 48 hoursCheck for downy mildew, which thrives in those conditions.
- Within a week of maturityHarvest-window reminder based on when you planted.
Sunflower questions
- When should I plant sunflower?
- Sow outdoors from your last spring frost to 3 weeks after it.
- How long do sunflower seeds take to germinate?
- Usually 7–10 days at a soil temperature of 18–24 °C.
- How long until I can harvest sunflower?
- About 60–90 days after sowing, depending on variety and weather.
- How far apart should I plant sunflower?
- Allow 45–90 cm between plants.
- What grows well with sunflower?
- Good neighbours include cucumber, squash, corn, tomato.
Growing guide written by Tomatograph. Planting figures from openplantdb (CC0 1.0). Zone frost dates are averages from openplantdb (CC0 1.0).