Sunflower
Helianthus annuus · Asteraceae
📷 Jon Sullivan · Public domain
The gardener's calendar
It's peak harvest for sunflower: pick regularly and at the right stage to boost production and extend the season.
ID card
- Foliage
- Deciduous
- Flowering
- July to September
- Adult size
- 1.5 to 2.5 m in height
- Growth
- Very fast
- Hardiness
- Annual, frost-tender
- Origin
- North America (Mexico)
- Soil type
- Rich, well-drained, slightly alkaline
- Exposure
- Full sun
✓ Taxonomy verifiedSource: AI estimate · hardiness: reliability high.
Expert tips
The key tip
Plant in rich, well-draining soil and stake as soon as the stem reaches 30 cm: giant sunflower varieties topple in the wind without support. One deep watering per week is enough once established.
The common mistake
Sowing too early or too densely: many gardeners sow in March and seedlings become leggy, or space them poorly and end up with thin, sparsely-branched stems.
The pro's trick
Pinch the apex at 30-40 cm height if you want several lateral flowers instead of one massive one: you'll get more small honey-producing flowers, perfect for bees.
Seasonal watch
July-August: watch out for aphids and slugs attacking young flower heads. Spray black soap as a preventative as soon as you spot the first leaf damage.
Care
Exposure
Sunflowers require a minimum of 6 to 8 hours of direct sunlight daily for abundant flowering and properly oriented flowers. Place yours in an open location, away from shade cast by trees or buildings. The more sunlight you give it, the more vigorously the plant develops and the larger the flower head becomes.
Watering
Water regularly during the growth period, especially during summer heat and when flower buds are forming. The soil should remain moist but not waterlogged: a deep watering once or twice weekly is usually sufficient depending on conditions. Gradually reduce watering after flowering.
Soil and planting
Enrich the soil with compost or organic matter before planting to encourage strong growth. Ensure adequate drainage to prevent root rot. Sunflowers appreciate neutral to slightly alkaline pH and tolerate poor soils, but thrive best in rich, crumbly earth.
Fertilizing
Apply balanced fertilizer at planting time or two weeks after sowing to establish good growth. You can reapply at the start of flowering to support flower formation. Fertilizer too high in nitrogen will promote foliage at the expense of flowers.
Pruning and staking
Pinch back the top lightly when the plant reaches 30 to 40 cm to encourage branching and multiple smaller flowers. For giant varieties (over 1.5 m), install a stake at sowing time to prevent the plant from being blown over by the weight of the flower head. Remove faded leaves at season's end if desired.
Diseases and pests
Sunflowers can be affected by mildew in prolonged humid conditions and by various fungal diseases. Ensure good air circulation and avoid overhead watering. Aphids and wireworms can occasionally cause problems. Regular inspection allows you to intervene quickly if needed.
Did you know?
The sunflower owes its name to the remarkable ability of its young flowers to track the sun's movement across the sky (heliotropism), a phenomenon called "nyctinasty." This solar dance stops once the flower matures, which typically turns to face east to absorb morning warmth, thus attracting pollinators. The Aztecs venerated this plant and associated it with their sun deities long before Van Gogh made it immortal in his famous series of paintings in the 19th century.
Where to buy it
Plant in spring or early autumn, avoiding spells of intense heat. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, April, May, September.
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Tips generated and checked by Viridia — adapt them to your local climate.