Sunflower

Sun

Full sun; give it at least 6-8 hours of direct sunlight daily and shelter tall plants from strong winds.

Water

Water seedlings regularly. Once established, water deeply during dry spells, especially while buds develop and seeds fill; avoid waterlogged soil.

Soil

Well-drained soil enriched with compost; tolerates clay, loam or sand if drainage is adequate.

Height

Typically 3-10 ft (0.9-3 m); dwarf varieties may reach only 1-2 ft (0.3-0.6 m), while giant types can exceed 12 ft (3.7…

Spread

1-3 ft (0.3-0.9 m), depending on variety and branching habit.

Flowers

Summer to autumn; usually yellow rays around a brown centre, with cream, orange, bronze and deep red varieties also available.

Foliage

Large, rough, hairy green leaves, usually broadly heart-shaped with toothed edges.

Growth

Fast; flowers within one growing season.

Care needed

Low

• Sow directly after the last frost once the soil has warmed; protect emerging seedlings from slugs and birds.
• Thin seedlings to the packet spacing, usually 12-24 in (30-60 cm), allowing more room for giant or heavily branching types.
• Water deeply at the base during dry weather; check container plants daily in hot conditions.
• Mix compost into the soil before sowing; avoid excessive nitrogen, which encourages leaves at the expense of flowers.
• Stake tall varieties early, using loose ties that will not cut into the stems.
• Mulch after seedlings are established, keeping mulch away from their stems.

Pruning. Remove faded heads from branching varieties to encourage more flowers, but leave selected heads to ripen for birds or seed harvest. Do not pinch single-stem varieties if you want their main flower; cut dead stems at ground level after the season ends.

Early spring

Choose varieties suited to your space and prepare a sunny bed with compost.

Spring

Sow outdoors after frost danger has passed and the soil has warmed; in short-season areas, start in individual pots a few weeks earlier.

Late spring

Thin or plant out seedlings, protect them from slugs, and install supports for tall varieties.

Early summer

Make a second sowing where the season is long enough, and begin deep watering during dry spells.

Summer

Cut flowers as the ray petals begin to open; deadhead branching plants unless saving seed.

Autumn

Leave ripe heads for birds or harvest when the backs turn yellow-brown and seeds loosen; dry harvested heads somewhere airy and protected.

Late autumn

Cut down dead stems, leaving roots to decay in the soil; remove diseased material.

• Plant tall varieties at the back of sunny borders with ornamental grasses and cosmos for height and late-season colour.
• Use a row beside a vegetable plot as a temporary summer screen, positioned so it does not shade sun-loving crops.
• Grow dwarf varieties in large containers near a sunny entrance or patio.
• Include branching, pollen-bearing varieties in wildlife borders to provide flowers for insects and seed heads for birds.
• Grow single-stem varieties in a cutting patch for large, straight-stemmed flowers.

Garden styles it suits: Cottage garden, Potager (kitchen garden), Farmhouse, Wildlife garden, Pollinator garden and Edible landscape.

Plant it with: Cosmos, Zinnia, French marigold, Nasturtium, Purple coneflower and Switchgrass.

Wildlife: Pollen-bearing flowers attract bees and other flower-visiting insects; ripe seeds feed finches and other seed-eating birds. Pollen-free cutting varieties provide no pollen, although some still offer nectar.

• Slugs, snails and birds can destroy seedlings: inspect frequently, use suitable slug controls and protect young plants with secured mesh that cannot trap wildlife.
• Aphids cluster on shoots and buds: wash them off with water and encourage ladybirds, lacewings and other predators.
• Powdery mildew coats leaves in dry, crowded conditions: improve spacing, water at soil level and remove badly affected leaves.
• Plants lean or topple in wind: stake early, avoid overfeeding with nitrogen and choose shorter varieties for exposed sites.

Not known to be toxic to cats, dogs, horses or people. Sunflower seeds are edible, but the tough shells should be removed; eating large amounts of leaves, stems or shells may cause digestive upset. Seeds can cause allergic reactions in susceptible people.

• Jerusalem artichoke (Helianthus tuberosus)

  A perennial that spreads through underground tubers, forming colonies with smaller yellow flower heads; annual sunflower has no persistent tuber crop.

• Maximilian sunflower (Helianthus maximiliani)

  Has narrow, often folded leaves and many smaller yellow heads along tall stems; it is a perennial rather than an annual.

• Mexican sunflower (Tithonia rotundifolia)

  Usually has orange to orange-red flowers with raised yellow centres and broad, often lobed leaves, rather than the large brown-centred heads typical of common sunflower.

Helianthus comes from the Greek words for sun and flower, while annuus means annual.

Propagation. Grow from seed, sown about 1 in (2.5 cm) deep after frost danger has passed. Direct sowing avoids root disturbance; if starting indoors, use individual pots and transplant while young. Saved seed from hybrids may not resemble the parent, and plants can self-sow where seed falls.

Accepted botanical name

Helianthus annuus

In the US and Canada

Native in the lower 48 states. Introduced in Alaska, Canada, Hawaii, Puerto Rico and St. Pierre and Miquelon.

Native range

Arizona, California, Mexico Central, Mexico Northeast, Mexico Northwest, Mexico Southwest and Nevada.

Measured

Soil pH 5.5 to 7.8. Average height 94 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.