Quick, plain-English answers to the questions people ask most about growing sunflowers. For the full detail on any of them, follow the links through to the rest of the Grow Guide.
It depends entirely on the variety. Dwarf types stay under 60 cm, common garden sunflowers reach 1.5–2.5 m, and giant varieties can top 3–4 m with good care. The world record is a remarkable 10.90 m (35 ft 9 in). See our types guide to pick the right one, and the records page for the giants.
Most take about 11 to 18 weeks from sowing to full flower, with giants at the longer end. Seeds germinate in 7–14 days, then growth accelerates through mid-season before the plant buds and blooms. There's a full timeline in our growing tips.
A lot — at least 6 to 8 hours of direct sun a day, and more is better. The sunniest, most sheltered spot you have will always beat a shadier one. Too little light gives you thin, weak, leaning plants.
Deeply and regularly, rather than little and often. Keep the soil consistently moist, especially before flowering. In hot, dry weather or in pots, that can mean watering every day or two. Always aim at the soil, not the leaves.
Most garden sunflowers are annuals — they grow, flower and die in a single year, so you sow fresh each spring. A few perennial species do return, but the tall, big-headed types people usually grow are annuals. The trick is to save seed from your best plant to grow again next year.
Young, growing sunflowers do — they track the sun east to west by day and reset overnight. Once the flower fully opens and the stem stops growing, it settles permanently facing east. There's a whole page on the science of it: do they follow the sun?
A single large head can hold up to around 1,000–2,000 seeds, arranged in that beautiful spiral. The number depends on the head size and how well it was pollinated — and the spiral itself follows a lovely mathematical pattern.
Yes — choose a compact or dwarf variety, use a pot at least 30 cm wide and deep with drainage holes, and water and feed regularly (pots dry out and run short of food faster than open ground). Full guidance in growing in pots.
Sow after your last frost, once the soil is warm. In the UK that's usually April–May; elsewhere it shifts to suit the local season. Our sowing calendar breaks it down by region.
Usually watering (too much or too little), too little sun, transplant shock, or a pest. Check whether the soil is dry or soggy two inches down, and look under the leaves. Most problems are fixable if you catch them early — our problems & pests guide walks through each one.