PlantSowGrow
How to grow Sunflower (Giant Single)
Helianthus annuus
The classic towering sunflower with huge yellow heads — great fun for children and loved by bees and birds.
At a glance: Sow mid April to late May.
When to sow, plant and harvest
Timed for a typical UK garden (last frost mid-April). The app uses your own town's frost dates.
Growing Sunflower (Giant Single): what it needs
- Light
- Full sun · 6+ hours a day
- Watering
- Water in dry spells; pots daily in summer
- Soil
- Any well-drained soil
- Spacing
- 45 cm
- Height
- 2–3 m
- In pots
- Only in large containers
- Feeding
- Liquid feed weekly from midsummer for the biggest heads
- Hardiness
- USDA zones 2–11
- Difficulty
- Easy
Step by step
- Mid April – late May · around the last spring frost
Sow Seeds Outdoors
Sow thinly where they are to flower, in a sunny spot, into raked, weed-free soil. Sow 1 cm deep, one seed per pot.
- 7–14 days after “Sow Seeds Indoors” · Late April
Check Germination
Seedlings should appear in 7–14 days. Keep the soil moist. If sown outdoors, thin them to 45 cm apart once they have two true leaves.
- 14 days after “Plant Out” · Early May
Add Support
Push in canes or twiggy sticks and tie in stems before they flop.
- 71–101 days after “Check Germination” · Early July – early August
First Flowers — Deadhead Regularly
Snip off faded flowers every few days to keep new ones coming for months. Take a photo for your journal!
- Mid October – early November · around the first autumn frost
Clear or Collect Seed
When frost blackens the plants, pull them up for the compost heap. Leave a few seedheads first if you want to save seed.
More flowers to grow
Photo: böhringer friedrich / Wikimedia Commons (CC BY-SA 2.5)
