There are about 180 named species of Gardenia and all are characterised by the sweet strong smelling perfume produced by white to cream flowers.
Gardenias belong to the Rubiaceae family to which Coffee also belongs.
Gardenia jasminoides are the most well known and there is evidence of these being in cultivation in the Song dynasty (960-1279) from paintings of the period. It took until the late 1700's that Gardenia were first seen in English gardens.
Gardenia bushes grow from 1 to 15 metres tall so there is a species right for most positions in your garden in warm temperate to subtropical climates.
Many double flowering forms are available along with some almost yellow flowered forms. Of course there is a ground cover Gardenia which is a handy addition.
Gardenias like sunny to half sun or filtered light positions, free draining soil and that which has a pH of 5 and 6.5 (slightly acid). Acid soils dissolve elements that are then able to be accessed by the plant.
The leaves of Gardenia are glossy dark green but are the first indicators of deficiencies in the soil.
Yellowing of the leaves is called chlorosis. Often chelated iron and Epsom salts (magnesium sulphate) is used to correct deficiencies. Take care applying these elements, a little is best, so follow manufacturer's instructions.
Sometimes you will see unsightly black mould on the leaves and stems of plants; this is the result of scale insects sucking the sap the secreting a sticky fluid. That fluid is secondarily affected by smut which has that characteristic black colouration. Easy to fix! Suffocate the scale with botanical oils and the smut will flake off in time. After a week, pick off a scale shell and if it's dry underneath then you have succeeded! You can also spray with wettable sulphur mixed to a paste like consistency first, then diluted to the required strength. WS is relatively safe to use and can be used to fix your aphis, mites and fungal problems.
Gardenias, glossy, well mannered, perfumed and neat. I'd give them 8.5/10.