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Growing Sunflowers


October 17, 2023


The Searles Gardening Team

Sunflowers make you smile; their wonderous blooms that follow the sun throughout the day are a marvel. In many regions in Australia, you may have two planting times for these plants. Typically, the seeds can be sown in tropical to subtropical regions in spring to autumn and late winter to early summer for temperate zones. Wait for the soil to warm in cooler regions, so plant in spring to early summer.

Sunflowers flourish in a wide range of soils. Ensure they receive adequate water and fertiliser when the buds first appear for a better flower crop.

Sunflowers come in a range of heights, colours, and flower types. When you look at Sunflower 'Teddy Bear', it appears more like a chrysanthemum and only grows to 45cm. In contrast, Sunflower 'Royal Velvet F1' grows to 1.5m. Once the plant is to height and the buds are starting to emerge, use a fertiliser higher in potassium, such as Searles Flourish Flower & Foliage or liquid Potash to boost flowers. Tall growing varieties may appreciate extra support or staking in windy conditions.

The time from planting seeds to producing flowers ranges from 10 to 14 weeks, depending on the variety. 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 until 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 mature, cut off the flower and leave some stalk. Like lavender, you can tie a few heads together and hang them 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 them a good shake or thump to dislodge the seeds. Those that don’t immediately fall away can be removed by hand. 

Fun Sunflower Facts

  • They are resistant to certain nematodes.
  • They are planted as a crop between certain crops in agriculture to guard against specific diseases.
  • They have a long tap root and can reach 1.5m, searching for moisture, which helps break up soil deep down.
  • Use Sunflower seeds for cooking oils, snacks, confectionary, animal/bird feeds and green manure.
  • Seeds and petals are edible, and the leaves can be steeped to make tea.
  • The tallest sunflower in the Guinness Book of Records is 9.17 metres, and a sunflower head is 82cm in diameter.  
  • If you collect seeds, it is not a guarantee that they will produce plants identical to the parent.