Anita Morton - Growing Gardens
Hibiscus can be very showy and decorative, but that display of flower power comes at a price. These plants (and Im referring to the common Hibiscus rosa-sinensis here) are gross feeders and can be a bit fussy about soil and climate. They do best in well-drained soil which is rich in organic matter, and because their roots are shallow, they also need to be mulched. They also need lots of sun, but protection from strong winds and frosts. If not given these conditions they grow slowly and their flowers are meagre.
Hibiscus should be fed with a complete fertiliser every two months throughout the flowering period. Whether youre using an organic or inorganic product, make sure that it isnt too high in nitrogen. Excessive nitrogen will encourage lots of growth at the expense of the flowers, and may cause buds to drop off without opening. Other causes include water stress and lack of nutrients.
The hibiscus beetle will also cause buds to drop if there is a heavy infestation. To determine if this is the problem, check deep inside the flowers when they are fully open. Hibiscus beetles are about 3mm long and rather like a black ladybird. They feed mainly on pollen, and can be hard to control as they live inside the flowers. The best treatment is to regularly rake up all fallen flowers and buds this is where the larvae live and feed, so you will interrupt the breeding cycle.
Hibiscus are easy to propagate by cuttings. Take tip cuttings about 10cm long now and strike them in a mixture of coir and grit. You can also take semi-hardwood cuttings when you prune the shrub in early spring. These plants are so easy to breed and propagate that plant enthusiasts have created hundreds of different varieties theres sure to be one to suit your garden.