Overview
What sunflowers need, how fast they grow, and whether they suit your garden.
Sunflowers range from pot-sized dwarfs to giants taller than a house, and their big seeds make them a favourite to grow with children. They need sun, shelter and rich soil. Bees crowd the flowers, and the heads that follow feed birds well into winter.
Quick facts
- Botanical name
- Helianthus annuus
- Soil pH
- 6.0 – 7.5
- Temperature
- 21 – 29 °C
- Hardiness
- Any zone, as an annual
- Time to harvest
- 70 – 100 days
- Height
- Up to 460 cm (181 in)
- Propagation
- Seed
Optimal growth
Killed by frost
Growing details
- Germination
- 7 – 14 days
- Spacing
- 30 cm (12 in)
- Sowing depth
- 25 mm (1 in)
- Frost sensitivity
- Frost tender
Growing calendar
- Start indoors: April, May
- Sow outdoors: April, May, June
- Flowering: July, August, September
- Harvest: August, September, October
In the UK, in pots from April, two to three weeks before planting out (Gardeners’ World, Illinois). In the UK, mid-April to mid-June once frost has passed (Gardeners’ World); early to mid-May in the US Midwest (Illinois). Up to 18 weeks after sowing, depending on variety (Gardeners’ World). After flowering, when heads droop and the back turns lemon-yellow; Iowa State gives 70 to 100 days from planting.
Is this plant right for you?
- Great with children
- Fast growing
- Needs full sun
- Loved by bees and birds
- Cut flowers
- Safe for pets
- Tall ones need staking
Good to know
Plan for support early: this plant needs a stake, cage or frame once it gets going. Wait until the last frost has passed before it goes outside.
Before You Grow
Choose a height and flower type, and the sunniest, most sheltered spot you have.
Many pollen-free cut-flower varieties give bees little or no pollen (Illinois).
What you need
Seed
Or plug plants and young plants (Gardeners’ World). See choose your sunflowers.
Small pots
Biodegradable ones spare the roots. See sowing.
Full sun and shelter
Compost or manure
For rich soil. See soil.
Canes and twine
For tall varieties. See staking.
Slug protection
For young seedlings. See pests.
Choose your sunflowers
Annual sunflowers range from about 15 cm (6 in) to over 3.5 m (12 ft), in yellow, cream, orange, red, burgundy and bicolours, single or double (Illinois, Iowa State).
Giant varieties reach 2.5 m (8 ft) or more, usually with one huge head, and need staking: ‘Russian Giant’ grows to about 3 m (10 ft), and ‘Cyclops’ to 4.6 m (15 ft) (Iowa State, NC State).
Semi-dwarf varieties, 0.9 to 2.5 m (3 to 8 ft), suit borders and rarely need staking (Iowa State). Some, such as the multi-stemmed ‘Pastiche’, branch and give many smaller flowers (NC State).
Dwarf varieties under 90 cm (3 ft), such as ‘Sunny Smile’ and ‘Junior’, suit pots and the front of beds (Illinois).
Pollen-free varieties are bred for cutting: no pollen to stain clothes, but little for bees (Iowa State, Illinois).
Perennial sunflowers such as ‘Lemon Queen’ come back each year; this guide covers annuals (Gardeners’ World).
Sunflower types compared
-
Giant
- Height
- 2.5 m (8 ft) and more
- Staking
- Needed
- Best for
- Height, seed heads, competitions
-
Semi-dwarf
- Height
- 0.9 to 2.5 m (3 to 8 ft)
- Staking
- Rarely
- Best for
- Borders, cutting, screens
-
Dwarf
- Height
- Under 90 cm (3 ft)
- Staking
- No
- Best for
- Pots, front of beds, children
-
Pollen-free
- Height
- 0.6 to 2.5 m (2 to 8 ft)
- Staking
- Sometimes
- Best for
- Cut flowers
From Iowa State and Illinois. For seeds and wildlife, grow a pollen-bearing variety.
Where sunflowers grow best
Sun. Full sun: six to eight hours of direct light (Clemson, Iowa State). Shade also encourages powdery mildew.
Shelter. Tall varieties with big heads can be damaged by strong winds; a sheltered spot helps (Illinois, Gardeners’ World).
Temperature. Best at 21 to 29 °C (70 to 85 °F), and not frost-tolerant (NC State). Young seedlings can survive a mild frost (Iowa State), but sow after the last frost.
Growth. Annual sunflowers can pass 2 m (6½ ft) in about three months, though height depends on variety, feeding, water and weather (Gardeners’ World).
Heliotropism. Young flower buds follow the sun; mature flowers stay facing east (Illinois).
- Sun
- 6 to 8 hours of direct sun
- Soil pH
- 6.0 to 7.5
- Best growth
- 21 to 29 °C (70 to 85 °F)
Soil
Sunflowers grow in most soils that don’t stay soggy (Illinois), but rich, fertile, well-drained soil gives the best plants (Iowa State, Gardeners’ World).
Preparation. Remove weeds, then dig in plenty of well-rotted manure or garden compost (Gardeners’ World). For direct sowing, rake to a fine, crumbly surface (RHS).
pH. 6.0 to 7.5 (Clemson).
Heavy feeders. Large and branching types especially benefit from organic matter and a slow-release fertiliser (Clemson).
Planting
Sow after the last frost, indoors in pots or direct, and handle the roots gently.
Sunflowers resent root disturbance: sow direct or in biodegradable pots (Iowa State).
When to sow sunflowers
Sow after the danger of frost has passed, once soil is above about 10 °C (50 °F) (Clemson).
In the UK, April to May, indoors in pots or direct from mid-April; as late as mid-June, though late sowings may not flower before autumn (Gardeners’ World).
Bought plants. Plug plants and young plants go out at the same time as home-raised ones (Gardeners’ World).
In the US, direct in early to mid-May in the Midwest, or indoors two to three weeks earlier (Illinois, Iowa State).
Little and often. Sow every one to three weeks for flowers all summer (Illinois, Gardeners’ World).
- After the last frost.
- April to May in the UK.
- Batches every couple of weeks.
How to sow sunflowers
The big seeds suit small hands. Seedlings appear in one to two weeks (Iowa State).
-
Indoors in pots
One seed per 10 cm (4 in) pot of peat-free multi-purpose compost; Iowa State prefers biodegradable pots that go straight into the ground (Gardeners’ World, Iowa State).
-
Keep warm
Cover with a clear bag in a warm spot until seedlings appear, then remove it (Gardeners’ World).
-
Or sow direct
Make holes about 30 cm (1 ft) apart, drop in a seed, cover and water well (RHS). The RHS sows 2 cm (¾ in) deep; Iowa State 2.5 to 5 cm (1 to 2 in).
-
Protect from slugs
From the moment seedlings appear. See pests.
-
Thin
Tall varieties to 60 to 75 cm (2 to 2½ ft) apart for air circulation (Iowa State).
Planting out
Bigger plants cope better with slugs: pot on into larger pots first if slugs are a problem (Gardeners’ World).
-
Harden off
Over two to three weeks (Gardeners’ World).
-
Wait for warm soil
Plant out once the soil has warmed and frost is over (Gardeners’ World).
-
Plant at the same depth
As in the pot, disturbing the roots as little as possible (Gardeners’ World, Illinois). Tear off any biodegradable pot rim above soil level: it wicks water away (Iowa State).
-
Water and stake
Water well and push in a cane beside tall varieties now (Gardeners’ World).
Care
Watering, feeding, staking, pinching and growing in pots.
Avoid high-nitrogen feeds unless you’re growing for height: they favour leaves over flowers (Iowa State).
Care by growth stage
Seedlings
Weeds: keep clear
Protect from slugs and snails. See pests.
Growing fast
Weeds: keep clear
Tall
Wind: check ties
Tie to a cane; pinch for more flowers. See staking.
Flowering
Water: keep it steady for seed
Cut for the vase or leave for seed. See harvesting.
End of season
Seeds: save some
Leave heads for birds, or save seed. See drying and using seeds.
Watering sunflowers
Water regularly while seedlings establish (Iowa State), soaking the soil around the roots whenever the surface has dried. Annual sunflowers suffer if they dry out, so water often, especially if you want height (Gardeners’ World).
Established plants are fairly drought tolerant, but water them in dry weather (Illinois). For the best seeds, don’t let them go short of water during flowering and seed formation (Iowa State).
Mulch 10 cm (4 in) of organic matter around, not touching, the stems once plants are 30 to 45 cm (12 to 18 in) tall (RHS).
Pots need watering daily in hot weather (Gardeners’ World). See containers.
Feeding sunflowers
For flowers. A mild liquid or slow-release fertiliser once plants establish; avoid high-nitrogen feeds, which favour leaves over flowers (Iowa State, Clemson).
For height. Gardeners’ World feeds weekly to fortnightly with a nitrogen-rich fertiliser, switching to a high-potash tomato feed just before flowering.
In pots. Feed fortnightly, nitrogen-rich then high-potash once flowering (Gardeners’ World).
Staking, pinching and deadheading
Staking. Tie tall varieties to a sturdy cane to stop wind rock and flopping, especially in exposed spots (Gardeners’ World, Illinois). It also keeps stems straight for cutting.
More, smaller flowers. Cut off the growing tip when the plant reaches about 1 m (3 ft) to make it branch (RHS).
Multiple heads up the stem are normal on branching varieties (Gardeners’ World).
After flowering. Deadhead, or leave the heads for the birds. Then pull up the plant and chop the thick stem for the compost heap (Gardeners’ World).
Sunflowers in containers
Sunflowers grow well in pots, though not as tall as in the ground. Dwarf varieties suit containers best (Gardeners’ World, Illinois).
Pot. Pot seedlings on into a 30 cm (12 in) pot of peat-free loam-based compost with added organic matter (Gardeners’ World).
Care. See watering and feeding; stake taller varieties (Gardeners’ World).
Problems
Slugs on seedlings, wind, hungry birds, and a few leaf diseases.
Common sunflower problems
Sunflowers are generally trouble free once past the seedling stage (Gardeners’ World). Match what you see to its likely cause.
Shorter than the packet says
- Food
- Water
- Weather
Height depends on feeding, water and weather (Gardeners’ World).
Black spots on leaves
- Sooty mould
Mould on honeydew from aphids. It fades as plants age; rub off aphids if you like (Gardeners’ World).
Yellow lower leaves on seedlings
- Normal
The seed leaves die back once true leaves grow (Gardeners’ World).
Poorly filled seeds
- Water stress
Iowa State keeps plants watered through flowering and seed formation for the best seeds. Check heads are plump before cutting. See watering.
More problems with sunflower
Common pests
Slugs and snails
The main threat to seedlings, especially in damp weather. Grow plants on in pots until they are bigger before planting out, and check seedlings in the evening (Gardeners’ World, RHS).
Birds and squirrels
Eat the ripening seed. Net or bag the heads, or remove the leaves nearest the head so birds can’t perch (Illinois, Iowa State).
Caterpillars, beetles and weevils
Chew leaves or heads, but rarely need action (Illinois, NC State).
Common diseases
Powdery mildew
White coating on leaves in humid weather. Space plants properly and grow them in full sun (Illinois, Iowa State).
Downy mildew
An occasional problem (Clemson). Pale patches on top of the leaves with fuzz below; space plants for air and clear affected plants at the end of the season.
Leaf spots and rust
Spots or rusty pustules on the leaves (NC State). Remove badly affected leaves; they rarely harm the flowers.
Harvest & Use
Cutting flowers for the vase, and harvesting, drying and using seed heads.
Cut flowers and seed heads
Cut flowers. Cut as the flowers begin to open, in the cool of the morning. Cut stems at an angle and strip most leaves, especially any below the water line (Illinois).
Seed heads. Seed matures 70 to 100 days after planting (Iowa State). Heads are ready when they droop, the back turns lemon-yellow to brown, and the small central florets rub off easily. Check that the seeds are plump and filled (Iowa State, Illinois).
Cutting. Take the head with about 30 cm (1 ft) of stem (Illinois).
Birds. Protect heads you want to keep. See pests.
- Cut flowers as they open.
- Seed heads when they droop.
- Take 30 cm (1 ft) of stem.
Drying and using sunflower seeds
Drying. Hang heads in paper bags or muslin somewhere dark, dry and airy until the seeds come away easily: a couple of weeks (Iowa State) to several weeks (Illinois).
Removing seed. Rub the dried head over newspaper and the seeds fall away (RHS).
Eating. Roast them or eat them raw, removing the tough seed coat (RHS, Gardeners’ World). Petals and young leaves can go in salads (RHS).
For birds. Leave some heads standing into winter as natural bird feeders (NC State).
Propagation
Saving your own seed to sow next spring.
Saving sunflower seed
Annual sunflowers flower, set seed and die in one year, so seed is the only way to grow them again (Gardeners’ World).
Collect. Leave the head on the plant at least two weeks after the petals fade, then dry it as for eating (RHS). See drying.
Dry and store. Spread the seeds on kitchen paper for a few days, then keep them in a paper envelope somewhere cool, dry and dark (Gardeners’ World, RHS).
Sow in pots from April the next year (Gardeners’ World).
Self-sown seedlings. Dropped seed comes up the following year, and plants can become weedy; pull any you don’t want (NC State).
More to Explore
Short answers, guides that pair well with sunflowers, and the sources behind this one.
Frequently asked questions
When should I plant sunflower seeds?
After the last frost: April to May in the UK, as late as mid-June; early to mid-May in the US Midwest. See when to sow.
How deep do I plant sunflower seeds?
About 2 to 5 cm (¾ to 2 in) deep; sources differ. See sowing.
How long do sunflowers take to grow?
Up to 18 weeks to flower; seed ripens after that, 70 to 100 days from planting by Iowa State’s count. See harvesting.
Do sunflowers need staking?
Tall varieties do, especially in windy spots. See staking.
Can I grow sunflowers in pots?
Yes, dwarf varieties especially. See containers.
Are sunflowers safe for pets?
Gardeners’ World describes them as non-toxic to pets and people.
When do I harvest sunflower seeds?
When the head droops and its back turns yellow-brown. See seed heads.
Do sunflowers follow the sun?
Young buds do; mature flowers settle facing east.
Related guides
Sources
- Sunflower growing (opens in a new tab) Royal Horticultural Society
- How to grow sunflowers at home (opens in a new tab) University of Illinois Extension
- Growing sunflowers and their varieties (opens in a new tab) Iowa State University Extension and Outreach
- Let’s grow sunflowers (opens in a new tab) Clemson Cooperative Extension
- Helianthus annuus (opens in a new tab) NC State Extension Gardener Plant Toolbox
- How to grow sunflowers (opens in a new tab) BBC Gardeners’ World