How to grow sunflowers and best varieties

Sunflowers add a cheerful dash of late-summer colour to our borders. They’re easy to grow, attractive to all sorts of pollinating insects and produce striking cut flowers. It’s always tempting to grow the tallest varieties and try to beat a record. But the dwarf varieties are extremely versatile, with single flowers or numerous heads and different colour combinations. 

Which? Gardening magazine  trialled different varieties of tall and dwarf types to find the best ones.

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Key facts

PLANT TYPE Hardy annual

POSITION Full sun

SOIL  Well drained

How to grow sunflowers: month by month

Best sunflower varieties

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Full testing results for sunflowers

Dwarf sunflowers

USING THE TABLE: OVERALL RATING Ignores price and is based on: suitability for hedging 20%, flower duration 20%, flower impact 20%, foliage 15%, seedhead 15%, pest & disease resistance 10%.

Tall sunflowers

USING THE TABLE Height and spread measured in full bloom. PERFORMANCE Germination rating based on the proportion of seeds that successfully germinated. Flowering duration based on the number of weeks they were at peak flowering. Flowering impact based on an assessment of the visual impact at flowering peak, taking into account size, colour and number of blooms. Pest and disease resistance based on the number of plants affected and the severity of any problems. Garden worthiness is a subjective rating and based on how this plant compares to others of its type, taking into account its health, vigour, display, form and habit, and whether the assessor would grow it again. OVERALL RATING Ignores price and is based on: flowering duration (30%), flowering Impact (30%), garden worthiness (20%), germination rating (15%) and pests and diseases (5%).

How we test sunflowers

In May, we sowed a row of each variety directly into the bed  of the Which? Gardening magazine trial ground, in pairs of seeds, 30cm apart. Once they were established, we removed the weaker of each pair of plants. As they started to flower, we measured the plants’ height, and the size and number of flowers. All the varieties were rated for their visual impact, and how long they flowered for. We also noted if they suffered from any problems with pests and diseases.

Caring for your plants

Sowing

In our trials, we've found that plants grown from directly sown seeds are much stronger than those that have been transplanted. Sow two seeds per hole, 1cm deep, in a sunny, free-draining bed in May. Once they are around 5cm tall, remove the weaker of the seedlings. Dwarf varieties should be sown about 15cm apart and taller varieties 30-45cm apart. Dwarf varieties can be grown in patio pots. Taller varieties need staking with a bamboo cane. Water well and protect them from slugs while young.

Feeding the birds

Once flowers have finished, leave the seedheads on the plants where they will attract birds that feed on them during early autumn.

Common growing problems

Powdery mildew

Look out for powdery mildew. This appears during mid-summer as a white, powdery coating on the leaves, which will quickly slow plant growth. Plants are more prone to attack during dry spells, so keep them well watered.

Read more about powdery mildew