This is the most common species of these frost-tender evergreen shrubs and it hails from south-east China, Taiwan and Japan. I have previously referred to it as Gardenia angusta, which is now a synonym. It has lush, shiny green leaves that allow it to fit in well to a semi-tropical style garden. The thick waxy petals of the highly perfumed flower are usually formed into a kind of a double rosette, and can vary in size from petite in the prostrate cultivar 'Radicans' (ht 50cm) to large in the cultivar 'Grandiflora' (ht 2m). Medium-sized 'Florida' (ht 1m), the one I grow, is the most well known.
Gardenia are very suited to our Sydney climate, as they enjoy warmth and humidity. Unfortunately, the plants have suffered from over-exposure in recent years, being beloved by many landscapers to use as hedging. I have never had a lot of luck growing them in the garden, as I found they became lanky and lacked a good form, so now I grow them in large pots, where they flower for many months from late spring into autumn, most profusely in November and December.
Generally, they enjoy a lightly shaded position with neutral to slightly acid soil which is well drained and rich in humus. Morning sun and afternoon dappled light is the ideal position for them. They don't like to be exposed to the hot afternoon sun in summer, as their small root system cannot cope with the rapid loss of water through the leaves. They do like adequate moisture and regular liquid fertiliser in the growing season to give optimum blooms, but the soil needs to be well drained. I shape mine in early spring (late August or early September) if they look rangy, giving them a complete plant food at the same time. Mulch around the plant with cane mulch or lucerne to retain moisture. Give them a liquid feed every fortnight during the warmer months - ideally one suited to acid-loving plants. They can become a bit woody and straggly with age and may need to be replaced every so often. It is a good idea to groom them of their dead flowers, as these become brown and unattractive, and tend to hang onto the bush.
Propagation is by semi-hardwood cuttings taken with a heel of old wood in autumn or winter. Sometimes the lower leaves become yellow and it is thought that magnesium should be applied to correct a deficiency, but often this is simply due to cold weather in spring interfering with normal root functioning. Scale and sooty mould can be controlled with a few sprays of Eco Pest Oil. Gardenia belongs to the Rubiaceae family of plants, which contains mainly warm-climate plants, such as Bouvardia, Pentas, Ixora, Mussaenda as well as the coffee plant, Coffea.
Gardenias are lovely in a vase.