Evergreen varieties of hibiscus will grow in tropical to warm-temperate climates, provided the area is free of frost. Deciduous forms, such as Hibiscus syriacus, will also grow in cool-temperate and frosty climates. Hibiscuses can be planted at any time of year, but it’s best to plant deciduous forms during autumn, so they have time to establish their roots before winter sets in.
These gems are sun lovers, so plant in full sun and protect from strong winds.
Hibiscuses grow best in well-drained, slightly acidic (pH 6-6.5) soil. The one exception is H. syriacus, which is tolerant of alkaline soils. Before planting, ensure you improve the soil with well-rotted compost or manure. These plants also grow well in pots. Plant them up with an acidic potting mix such as Brunnings Azalea And Camellia Potting Mix or Osmocote Professional Rose, Gardenia, Azalea & Camellia Mix.
During the growing season, water regularly, and ensure drainage is good. Mulch the surrounding area with organic mulch, straw, hay or sugarcane, ensuring it doesn’t touch the stem. This will help keep the roots cool and moist in summer.
These plants respond well to fertiliser. Choose one that encourages blooms, and is high in nitrogen and potassium, such as Yates Thrive Soluble Flower
& Fruit Plant Food or Miracle-Gro MaxFeed Flowers & Blooms Soluble Plant Food. You can also add a fish emulsion or seaweed extract to this feeding mix. Apply before and throughout the growing season (August through to March) as this will help intensify bloom colour and promote healthy growth.
Check plants for the hibiscus flower beetle. These tiny black insects burrow their way through flower buds and foliage, leaving gaping holes. Use a systemic insecticide, such as Yates Confidor or Defender MaxGuard to control infestations.
The best time to prune evergreen types is at the start of the growing season or when the last frost has passed – usually in September. They flower on new season wood, as do the deciduous types, which should be pruned in winter. Prune just above a bud and remove any weak or dead branches. If left unpruned, hibiscus shrubs will become scraggy and shapeless, with fewer flowers and smaller, duller blooms. Prune off one-third of the plant to help rejuvenate tired-looking plants.