How to Grow Sunflowers from Seed in Australia
Botanical Name: Helianthus annuus
Common Name: Sunflower
Plant Family: Asteraceae
Sunflowers are tall, bright flowers that follow the sun as they grow. Their big yellow blooms attract bees and make great cut flowers or seed producers. This guide will show you how to plant, grow, and care for sunflowers in your garden or in pots.
What Are Sunflowers?
Sunflowers are annual plants native to North America. They grow from a single thick stem and can reach over 3 metres tall. Some produce just one large flower, while others form many smaller heads.
Popular Varieties:
- Sunbird
- Russian Giant
- Evening Sun
- Teddy Bear
- Velvet Queen
- Mammoth Grey
Why Do They Follow the Sun?
Young sunflower plants turn their heads to follow the sun each day—a behaviour called heliotropism. Once mature, their flowers usually stay facing east. The spirals in their seeds follow the Fibonacci sequence, just like in nature.
How to Use Sunflowers
Sunflowers can be grown for their seeds, which are used in snacks, oil, and birdseed. You can also eat the young shoots as microgreens. They taste nutty and crunchy—perfect in salads or wraps.
How to Prepare Your Soil
- Choose a sunny spot with well-drained soil.
- Add compost or aged manure to improve nutrients.
- Use a slow-release fertiliser if growing for large flowers or seeds.
Growing in Containers
Pick a pot at least 40 litres in size and fill it with premium potting mix. Choose a shorter variety for pots and make sure the container gets full sun.
When to Sow Sunflowers in Australia
How to Plant Sunflower Seeds
Direct Sowing
- Plant seeds 10 mm deep straight into the garden.
- Space 15 cm apart for smaller flowers or 35 cm apart for larger ones.
- Keep rows at least 2 metres apart.
- Keep soil moist during germination.
- Seeds sprout in 7–14 days when soil is 21–30°C.
Raising Seedlings
- Use seed trays filled with seed-raising mix.
- Plant 10 mm deep and keep the soil moist.
- Transplant when seedlings are 5–10 cm tall.
Tip:
Sunflowers grow best when sown directly into the soil. Their long roots don’t like being disturbed, so transplanting can cause stunted growth.
Growing Sunflowers
Spacing
Space plants 15–35 cm apart. Close spacing = smaller blooms. Wide spacing = larger flowers.
Watering
Water deeply but not too often. Check the top 5 cm of soil—if dry, it’s time to water. Overwatering can lead to root rot.
Staking
Tall sunflowers or those with large heads may need support. Use garden stakes, bamboo, or trellis and tie loosely with twine.
Sunflower as a Companion Plant
- Don’t plant near potatoes or pole beans—they compete for nutrients.
- Can be used as living trellises for cucumbers or climbing veggies.
- Protects zucchinis, pumpkins, and squash from aphids.
Pests and Insects
Sunflowers attract both good and bad bugs. Bees and pollinators love them, but you’ll also see sap suckers like aphids or leafhoppers.
- Use insect netting when flowers begin forming to protect from pests.
- Encourage ladybugs and hoverflies—natural aphid predators.
- Pick off caterpillars or spray neem oil if infestations occur.
Diseases to Watch For
Common issues include:
- Fusarium wilt: Yellowing and wilting of leaves
- Downy mildew: White fuzz on undersides of leaves
- Root rot: From overwatering or poor drainage
To prevent problems, rotate crops yearly and avoid planting in the same spot twice in a row.
Harvesting Sunflower Seeds
Sunflowers are usually ready to harvest around 90 days after planting. Wait until the back of the flower head turns brown and dry. The seeds should feel firm.
To Harvest:
- Cut the head with 30–45 cm of stem attached.
- Hang upside down in a dry, well-ventilated place.
- When dry, rub or tap the head to release seeds.
Storing Seeds
- Dry seeds completely before storing.
- Use airtight containers for seed saving or snacking.
- Eat raw, roast for flavour, or save for next season.
More Sunflower Tips
- Plant in full sun for at least 6 hours a day.
- Birds love seeds—use netting if you plan to harvest them.
- Remove spent flowers to encourage more blooms.
For more detailed tips, check this helpful article from the University of Georgia Extension:
Growing Sunflowers in the Home Garden.