There are various sunflower varieties to choose from, including the tall giant forms, which can reach up to 1.5-2 m tall and typically take up to 12 weeks to bloom. Due to their height and large heads, they can become quite top heavy (especially once the flower heads are full of seeds), so they will need protection from strong winds and rain and may require staking to prevent them from toppling over. If you don’t have the space, consider growing dwarf or smaller varieties. They grow between 30-50 cm tall and only take 8-10 weeks to flower. Both compact and tall growing varieties are available in the classic golden yellow hues, but they’re also available in orange, bronze, russet reds and bi-colour combos.
Sunflowers are easy to grow from seeds or seedlings. Read on to find out how you can grow sunflowers in the garden or in pots.
Sunflowers can be grown in all climate zones across Australia. If you live in cool or cold climates, wait until the chance of last frost has passed before sowing seeds or planting seedlings. For most parts of Australia, you can plant sunflowers from spring to early summer. Refer to the back of the seed packet or plant label for more detailed information.
Choose a sunny spot in your garden that receives between 6-8 hours of sunlight. If you’re growing giant or tall sunflowers, ensure the position is sheltered from strong winds.
Ideally, the soil will be moist but well-draining. If you find that your soil is hard to dig into or doesn’t drain very well, improve it by adding organic matter, like Yates Dynamic Lifter Soil Improver and Plant Fertiliser, and liquid gypsum. If the soil is too difficult to work with, consider planting into raised garden beds or pots. When planting in pots, use a quality potting mix, like Yates Premium Potting Mix. See How to grow sunflowers in the garden or How to grow sunflowers in a pot for more detailed planting information.
Once the buds start to appear, feed with a fertiliser high in potassium, like Yates Thrive Roses & Flowers Liquid Plant Food. This will help encourage bigger and healthier flower heads. Feed once every 2 weeks for best results.
Water well and deeply as plants are establishing. Once established (after 4-6 weeks), they require very little watering, except on hot or dry days.
As tall or giant sunflowers grow, they become quite top heavy and can bend or snap, especially if there are strong winds and rain. Drive a sturdy bamboo or wooden stake into the soil next to the plant and secure with garden twine or a piece of old hosiery.
How to harvest the seeds
As the flower heads mature, they form seeds in the centre of the head. To save the seed for next season’s planting or to harvest the seeds for cooking, allow the head to dry out on the plant. You may need to cover the heads with paper bags or netting as birds will find this free feed very attractive. Once the flowers begin to yellow and die, cut the heads and store them upside down in a dry spot. When ready, the seeds should be fairly loose in the head. Simply remove the seeds by tapping on the back of the head and allowing them to collect in a bucket or tray below. If you are saving seed, store them in an air-tight container, in a cool dry spot, out of direct sunlight.
Pests and diseases
Snails and slugs love to chew on the foliage of young seedlings. Protect plants by scattering Yates Blitzem Snail & Slug Pellets around small seedlings and nearby plants. Repeat in 7-10 days, if necessary. Sap-sucking insects like whitefly, thrips and aphids also love the foliage. They’re often hiding in new growth or under the foliage, so be sure to check plants regularly. If you see them, treat with Yates Nature’s Way Citrus & Ornamental Spray.
Sunflowers are also susceptible to a variety of fungal diseases, including rust and powdery mildew. Spray at first sign of the disease with a suitable garden fungicide, like Yates Rose Shield Black Spot and Insect Pest Killer.