How to Grow Sunflowers

Sunflowers are fast-growing, cheerful plants that are easy to grow from seed and incredibly rewarding for new gardeners. They thrive in warm weather, grow quickly, and produce bold blooms that make excellent cut flowers and garden features.

When to Grow Sunflowers in Australia

Sunflowers are a warm-season annual and are sensitive to frost.

Best time to sow: Spring to early summer
Sow once all risk of frost has passed and soil has warmed
In most regions, sow from September to January
In warm climates, sowing can continue into late summer

Sunflowers grow rapidly in warm conditions and flower within 8–12 weeks from sowing.

How to Sow Sunflower Seeds

Sunflowers grow best when direct seeded, as they dislike root disturbance. Raising seedlings is possible but not usually necessary.

Option 1: Direct Seeding (Recommended)

Choose a sunny position with well-drained soil
Sow seeds 2–3 cm deep
Space seeds according to variety (generally 30–45 cm apart)
Water well and keep soil moist until germination

Seeds usually germinate in 7–10 days.

Thin seedlings if needed, keeping the strongest plants.

Option 2: Raising Seedlings

If starting early or in cooler regions:

Sow seeds into individual pots (sunflowers do not like transplanting)
Use a quality seed-raising mix
Keep warm and well lit
Transplant carefully while seedlings are still small

Avoid disturbing the roots when planting out.

Growing Conditions

Sun: Full sun (at least 6–8 hours per day)
Soil: Well-drained, moderately fertile soil
Water: Regular watering, especially during hot weather
Support: Taller varieties may need staking in windy areas

Sunflowers are heavy feeders and benefit from healthy soil, but avoid excessive nitrogen which can encourage leaf growth over flowers.

Ongoing Care

Water deeply rather than frequently
Keep weeds under control while plants are young
Stake tall varieties early if needed
Regular picking encourages more side blooms on branching varieties

Harvesting

For cut flowers:

Harvest when petals are just beginning to open
Cut early in the morning for best vase life

For seed heads:

Leave flowers on the plant until heads mature and dry
Protect from birds if saving seed