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Sunflower

Helianthus annuus

Flowers

Cheerful giant that tracks the sun and produces seed-filled heads loved by birds. Dwarf varieties work well in containers.

Overview

SunFull Sun
WaterMediumCalculate watering amount
Height100–300 cm
Spread40 cm
Spacing45 cm
Row Spacing75 cm
Germination7–10 days
To Harvest55–80 days

Companion Planting

Bad Companions

Potato

Toxicity

SeverityNon-toxic

Sunflowers are non-toxic to humans, dogs, and cats according to the ASPCA. All parts including petals, seeds, and leaves are safe.

Planting Tips

LocationFull sun (at least 6-8 hours of direct sunlight per day); shelter from strong winds for tall varieties.
SoilWell-drained, moderately fertile loam with a pH of 6.0-7.5; tolerates poor soils but thrives with some organic matter.
Sowing Depth2.5 cm
Planting Depth5 cm
WateringWater deeply once or twice a week; established plants are drought-tolerant but consistent moisture during flowering improves seed fill.

1 cm of water per m² equals 10 liters. Use the Watering Calculator for exact amounts.

FertilizingApply a balanced slow-release fertilizer at planting; avoid high-nitrogen feeds which promote foliage over flowers.

Care Tip: Stake tall varieties once they exceed 90 cm; deadhead spent blooms on branching types to encourage continued flowering.

Common Pests

Aphids

Symptoms: Clusters of small green or black insects on stems and undersides of leaves, causing curling and sticky honeydew residue.

Treatment: Spray with a strong jet of water or apply insecticidal soap; for severe infestations use neem oil.

Prevention: Encourage natural predators like ladybugs and lacewings; avoid excessive nitrogen fertilization.

Sunflower Head Moth (Homoeosoma electellum)

Symptoms: Larvae tunnel into developing flower heads, leaving frass and damaged seeds; webbing visible between florets.

Treatment: Remove and destroy infested heads; apply Bacillus thuringiensis (Bt) when larvae are young.

Prevention: Plant early to avoid peak moth flights; rotate planting locations annually.

Sunflower Beetle (Zygogramma exclamationis)

Symptoms: Skeletonized leaves with only veins remaining; adult beetles and larvae feed on foliage.

Treatment: Hand-pick adults and larvae from plants; apply neem oil or pyrethrin-based sprays for heavy infestations.

Prevention: Remove plant debris after harvest; practice crop rotation to break the beetle life cycle.

Common Diseases

Downy Mildew (Plasmopara halstedii)

Symptoms: Yellow-green patches on upper leaf surfaces with white-grey fuzzy growth underneath; stunted growth and distorted flower heads.

Treatment: Remove and destroy infected plants; fungicide seed treatments can protect young seedlings.

Prevention: Use resistant cultivars; avoid overhead irrigation and ensure good air circulation.

Sclerotinia Head Rot (Sclerotinia sclerotiorum)

Symptoms: Soft, watery rot on the back of the flower head that spreads inward; white cottony mycelium and hard black sclerotia appear on decaying tissue.

Treatment: Remove and destroy affected heads immediately; no effective chemical control once infection is established.

Prevention: Rotate crops on a 3-4 year cycle; avoid dense planting and overhead watering to reduce humidity.

Rust (Puccinia helianthi)

Symptoms: Reddish-brown pustules on the undersides of leaves that release powdery spores; severe infections cause premature leaf drop.

Treatment: Apply fungicides containing chlorothalonil or mancozeb at the first sign of pustules; remove heavily infected leaves.

Prevention: Plant resistant varieties; space plants for adequate airflow and avoid wetting foliage when watering.