No plant repays getting the details right quite like a gardenia. The perfume from a single flower carries across a courtyard, the glossy dark foliage looks good year-round, and a well-sited plant flowers for months through an Australian summer. Get the soil wrong, though, and you get the other gardenia - the one with yellow leaves that sulks for years while its owner keeps feeding it. The difference is almost always soil chemistry rather than care.
Quick facts
| Detail | What to expect in Australia |
|---|---|
| Botanical name | Gardenia augusta (also sold as G. jasminoides) |
| Mature size | 300 mm to 2 m depending on variety |
| Position | Morning sun, afternoon shade in hot climates |
| Soil | Acidic, pH 5.0-6.5, rich and free draining |
| Water | Consistent. Dislikes drying out and waterlogging alike |
| Flowering | Spring through summer, longer in warm climates |
| Frost | Moderately tender. Protect young plants |
| Best climates | Brisbane, coastal NSW, Sydney, Perth, warm Melbourne suburbs |
Which gardenia to plant
| Variety | Size | Flower | Best for |
|---|---|---|---|
| Florida | 1 m | Double, medium | The all-purpose garden gardenia, pots |
| Magnifica | 1.5-2 m | Very large double | Feature shrub, informal hedge |
| Aimee Yoshiba | 1.5 m | Very large, early | Cooler districts, long flowering |
| Radicans | 300 mm x 1 m | Small double | Groundcover, borders, low pots |
| Star | 1-1.5 m | Single, starry | Hardiest option, low hedging |
| Native gardenia | 4-6 m tree | Single white, scented | Shade tree for warm gardens |
For most gardens
Florida is the standard and deservedly so - about a metre tall, reliable flowering, and equally at home in a pot or a garden bed.
For the biggest flowers
Magnifica produces very large double blooms on a taller plant, and Aimee Yoshiba flowers earlier and copes better with cooler conditions, making it the pick for Melbourne and Adelaide gardens.
For a low edge
Radicans spreads to about a metre wide but stays only 300 mm tall - a genuinely fragrant groundcover for the front of a shaded bed.
The tough one
Star gardenia handles more sun and more neglect than the others and clips into a low hedge, though its single flowers are less showy.
The Australian native
Randia fitzalanii is not a true gardenia but carries the same intensely scented white flowers on an Australian rainforest tree reaching four to six metres. It is an excellent shade or screening tree for warm subtropical gardens and far tougher than the shrub gardenias.
Yellow leaves: the gardenia problem
Nearly every unhappy gardenia in Australia is showing a nutrient lock-out caused by soil pH, and feeding it more fertiliser makes no difference. Read the pattern:
- Yellow leaves with green veins, on new growth - iron deficiency, caused by alkaline soil. Very common near concrete, brick and limestone, or with hard bore water.
- Yellow leaves with green veins, on older growth - magnesium deficiency. Epsom salts at the rate on the pack fixes it.
- Uniformly pale yellow all over - nitrogen shortage, or cold soil in winter, which is normal and passes.
- Yellowing with leaf drop and wet soil - root rot from poor drainage.
The fix: test the pH. Gardenias want 5.0 to 6.5. Above that, iron and manganese become chemically unavailable no matter how much is in the soil. Apply chelated iron for a quick correction, and lower pH over time with elemental sulphur, compost and an acidic mulch. Use rainwater or filtered water rather than hard tap water where you can.
Where they grow in Australia
- Brisbane, Gold and Sunshine Coasts, northern NSW - ideal, with the longest flowering season.
- Sydney and coastal NSW - excellent in a sheltered spot with morning sun.
- Perth - grows well but the alkaline sandy soils make iron deficiency very common. Expect to manage pH actively.
- Melbourne and Adelaide - workable in warm sheltered positions. Aimee Yoshiba is the better choice, and pots let you shelter plants over winter.
- Canberra and cold inland - difficult. Frost and cold soil check growth badly.
How to plant
- Plant in spring once the soil has warmed.
- Morning sun, afternoon shade in most of Australia. Full afternoon sun scorches the leaves and stresses the plant.
- Enrich the soil heavily with compost and an acidic organic matter such as composted pine bark.
- Keep clear of concrete and brick foundations, which leach lime and raise pH exactly where the roots are.
- Ensure drainage. Gardenias want consistent moisture but rot in waterlogged soil.
- Mulch to 50 mm with an acidic mulch, kept off the stem.
Ongoing care
Watering
Consistency matters more than volume. Gardenias drop flower buds when they dry out, and rot when they sit wet. Deep watering two or three times a week through summer, less in winter. Mulch does most of the work of keeping moisture even.
Feeding
Use a fertiliser formulated for acid-loving plants - the same products sold for camellias and azaleas. Feed in early spring and again after the first flush of flowers. Avoid lime and dolomite anywhere near them.
Pruning
Light tip pruning after flowering keeps the plant compact and encourages branching. Gardenias flower on new growth, so pruning immediately after a flush gives the plant time to make more. Avoid hard pruning in autumn or winter.
Common problems and fixes
- Flower buds dropping before opening is the classic sign of inconsistent watering, or a sudden change in temperature or position. Mulch and water steadily.
- Yellow leaves with green veins means iron or magnesium lock-out from high pH. Chelated iron and Epsom salts, then correct the pH.
- Sticky leaves with sooty mould follows scale, mealybug or aphids. Treat with horticultural oil.
- No flowers on a healthy plant usually means too much shade or too much nitrogen.
- Brown scorched leaf edges is too much afternoon sun or salty water.
- Sudden wilting with wet soil is root rot. Improve drainage; a plant in a saucer full of water will not recover.
Growing gardenias in pots
Pots suit gardenias well and solve the pH problem entirely, because you control the mix. Use a premium potting mix for acid-loving plants, a container at least 400 mm across, and keep it where morning sun reaches the plant. Water consistently, feed twice a year, and repot every two or three years. In Melbourne and Adelaide a pot also lets you move the plant to shelter over winter.
Frequently asked questions
Why are my gardenia leaves turning yellow?
Almost always iron or magnesium lock-out caused by alkaline soil rather than a lack of fertiliser. Yellow leaves with green veins on new growth means iron; on older growth it means magnesium. Test the pH - gardenias need 5.0 to 6.5.
Why do the flower buds fall off before opening?
Inconsistent watering is the usual cause, along with sudden changes in temperature or being moved. Mulch well and water steadily rather than letting the plant swing between dry and soaked.
How much sun does a gardenia need?
Morning sun with afternoon shade in most Australian climates. Full afternoon sun scorches the foliage, while deep shade means few flowers. Around four to six hours of gentle light is ideal.
What is the best gardenia for a pot?
Florida for a classic metre-tall shrub, or Radicans if you want something low and spreading. Pots suit gardenias well because you control the potting mix and avoid the alkaline soil that causes most problems.
Is there an Australian native gardenia?
Randia fitzalanii, the native gardenia, is a different genus but carries similarly fragrant white flowers on a four to six metre rainforest tree. It is considerably tougher than the shrub gardenias in warm subtropical gardens.
Will gardenias grow in Melbourne?
Yes, in a warm sheltered position, though they are slower and flower for less of the year. Aimee Yoshiba handles cool conditions better than most, and growing in pots allows you to shelter plants through winter.
Ready to plant?
We grow the full gardenia range plus the native Randia fitzalanii. Browse our plants for partial shade, or plants for pots.
Related reading: soil types explained and natural privacy with Randia fitzalanii.
