Gardenia jasminoides and other Gardenia species, hybrids and cultivars
Gardenias are commonly used landscape plants in SEQld, but too often the dream of fragrant, milky-white blooms fails to match the reality of growing these plants in Queensland's increasingly hot and dry conditions.
Hints for growing gardenias well in SEQLD include a moist but well drained soil enriched with organic matter. They will need plenty of light for flowering but protection from the most punishing summer sun and drying winds. Morning sun or dappled sun all day would be appropriate.
These somewhat fussy shrubs will tend to drop their flower buds if they get stressed, such as a heat or cold shock, or drying out. Try to keep soil moisture consistent.
Fortunately, the common type sold locally as 'Florida' is a garden centre staple in SEQld and don't cost a lot in the smaller pot sizes. Why not buy a few plants and try them out in a different spots to see what works best in your garden?
Alternatively, try one in a tub in an azalea and camellia mix. Gardenias like soil on the acid side. A fertilser designed for other acid-loving plants like azaleas or camellias would also be suitable for gardenias.
Epsom Salts are sometimes recommended as a remedy for yellow leaves, but note that like any plant, a number of nutritional deficiencies/toxicites could cause yellowing of foliage.
Gardenias are prone to Sooty Mould
Prune after flowering. Avoid winter/spring pruning as this will result in loss of the autumn-initiated flower buds which normally bloom in late spring/early summer.
From general observation, the groundcover form 'Radicans" does seem to perform better locally than the larger shrub types. This can also be pruned to form a miniature hedge. So, these are also an alternative to try if you desire gardenia fragrance in the garden, but aren't having luck with other forms.
Most gardenias grown gardens here are cultivars of Gardenia jasminoides (synonyms G augusta, G. florida). However there are other species in cultivation.(Note from the Editor: If anyone knows of a retail supplier of Gardenia taitensis or Gardenia thunbergia in Australia, please get in touch). furthermore, there are plants commonly referred to by the name "Gardenia" which actually belong to other genera, such as the "mock gardenia" or the "native gardenia"
Gardenias in the Landscape
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Gardenia (cultivars unknown) growing in Queensland, Australia