Growing and planting sunflowers

Sunflowers, the bringers of joy, with their wondrous blooms that follow the sun throughout the day, are a marvel to behold.  In many regions in Australia, the prospect of two planting times for these plants can be quite exciting.

Typically, the seeds can be sown in tropical to subtropical regions from spring to autumn and late winter to early summer in temperate zones. It’s a thrilling wait for the soil to warm in cooler regions, heralding the arrival of spring to early summer, the perfect time for planting.

We generally look to plant seeds in spring, and in the lucky zones, you can plant seeds in late summer as well. Sunflowers flourish in a wide range of soils, and with a little extra care to fertilise and ensure they receive adequate, regular water when the buds first appear, you will produce a better flower crop. Once established, sunflowers are drought-tolerant but still need regular watering, especially during dry periods. Water deeply to ensure roots grow strong.

Sunflowers need full sun to flower well. Choose a location that gets at least 6-8 hours of direct sunlight daily. They prefer well-draining soil with a pH between 6.0 and 7.5. Plant sunflower seeds into Searles Planting Mix for garden beds or Searles Premium Potting Mix for small sunflower varieties in pots.

Sunflowers, with their range of heights, colours, and flower types, are a canvas of nature’s creativity. When you look at Sunflower ‘Teddy Bear,’ it appears more like a chrysanthemum and only grows to 45cm, while Sunflower ‘Royal Velvet F1’ grows to 1.5m, a testament to the diversity of these plants. Once the plant is at its height and the buds start to emerge, use a fertiliser higher in potassium, such as Searles Flourish Flower and Foliage Soluble Plant Food or Liquid Potash, to boost the flowers. Tall-growing varieties may appreciate extra support or staking in windy conditions.

Many varieties, from planting seeds to producing flower heads, take 10 to 14 weeks. They can stay in bloom for up to a month.  Many use the flowers as cut flowers or enjoy them in the garden.  If you want to collect the seed, leave the flower on the plant till the flower starts to fade. The seeds need this extra time to ripen, but be aware the birds love them, so once they begin to take an interest in the flower, it is time to harvest the seeds. Once the seeds are ripe, remove the flower and leave some stalk. Like lavender, you can tie a few heads together and hang upside down in a cool, dry place. From there, it can be as simple as putting them in a large bag or bucket and giving it a good shake or thump. Those that don’t immediately fall away will easily be removed by hand. If you collect seeds, it is not a guarantee that they will produce plants identical to the parent.

Look out for aphids, caterpillars, and birds. Fungal diseases like downy mildew can affect sunflowers. Ensure good air circulation and avoid overhead watering to prevent this.  

Fun Sunflower Facts

• Sunflowers are resistant to some nematodes. They are sometimes planted between certain crops in agriculture to guard against specific disease.

• They have a long tap root and can reach 1.5m, searching for moisture, which helps break up soil deep down.

• Sunflower seeds are used for cooking oils, snacks, confectionary, animal bird feeds and green manure.

• The tallest sunflower in the Guinness Book of Records is 9.17 metres and a sunflower head of 82cm diameter. 

Top sunflower varieties

Giant sunflowers

Sunflower ‘Russian Giant’  – 3m tall, classic bright golden-yellow flowers up to 50cm across

Tall sunflowers

Sunflower ‘Double Dazzler’ – 2m tall, with multi-petalled deep yellow flowers

Sunflower ‘Royal Velvet F1’ – 1.5m tall, with deep bronze coloured velvety petals

Sunflower ‘Lemon Queen’  – 2m tall, pale lemon flowers

Sunflower ‘Yellow Empress’ – 2m tall, with large bright yellow flowers and black centres

Dwarf sunflowers

Sunflower ‘Teddy Bear’ – 50cm tall, with round double yellow fluffy pompom flowers about 15cm in diametre

Sunflower ‘Dwarf Sensation’ – 20-30cm tall with bright yellow flowers, ideal for pots