There are many cultivars of Gardenia augusta, including groundcover, dwarf and medium-sized varieties, so there’s a gardenia for every size garden. All the cultivars also grow beautifully in containers, so even if you only have a small patio or balcony garden, you can plant a Gardenia.
Gardenia augusta is a fragrant flowering evergreen tropical plant that is a favourite in warm temperate and subtropical gardens worldwide. The common name, Cape Jasmine derived from the earlier belief that the plant originated in the Cape of Good Hope, South Africa. However, Gardenia augusta originated in Asia and is most commonly found growing in Vietnam, Southern China, Taiwan, Japan, India, and nearby regions of the subtropical eastern hemisphere. It is essential in all romantic and perfumed gardens, and makes a beautiful freestanding specimen shrub to plant close to a patio, entrance, garden bench or window; where its fragrance, shape and beauty can be appreciated; it also makes a good hedge or screening plant.
Mature Gardenia augusta shrubs usually have a round shape, growing +-1.8 to 2.5m tall, with almost an equal spread, producing their gorgeous fragrant flowers over a fairly long season from late spring to late autumn, with the main flush in the months leading up to Christmas. The flowers are white, turning to creamy yellow as they age, and have a waxy feel. Their powerfully sweet fragrance can perfume an entire room, making them a favourite with florists; and warm summer breezes will waft the scent through the whole garden, much to the delight of everyone. Fleshy or leathery berries follow the flowers, and the large leathery leaves are highly glossy and remain attractive throughout the year.
Cultivars are available that are distinctly different from the plant described above. Flowers can be white or yellow; and single, semi-double, or double rose-like forms are available.
(Gardenia ‘Florida’) produces large double white blooms and grows +-1.2 to 1.5m tall and almost as wide.
(Gardenia ‘Golden Magic’) has double cream flowers that turn butter yellow with age. It grows +-80 to 100cm tall and +-80 to 100cm wide.
(Gardenia ‘Professor Pucci’) produces large, double pure white flowers in profusion. It grows + -1.2 to 1.5m high and +-80 to 100cm wide.
(Gardenia ‘Impulse var Grandiflora Star’) produces single, pure white, star-shaped flowers and grows +-50cm high and 30cm wide.
(Gardenia ‘Four Seasons’) grows +-50cm high and 30cm wide and produces single pure white, star-shaped flowers.
(Gardenia ‘Impulse White Gem’) has small single white, star-like flowers. It grows +-40 to 50cm tall and +-40 to 80cm wide.
(Gardenia ‘Radicans’) is a compact and low-growing groundcover with very small leaves; +-30 to 40cm tall, and spreading +-80cm to 1m wide. It produces small (3cm) double white flowers and is often used for bonsai.
Gardenia’s are evergreen and grow best in warm, moist regions, but are semi-hardy to moderate frost if planted in a protected position in the garden. Select a site that receives semi-shade to sun, or morning sun. In very hot regions the plant will appreciate some shade in summer, during the hottest part of the day; but in cooler areas they are quite happy in full sun. Ensure that the planting site is protected from strong winds and that the soil drains well. Prepare the planting holes very well, incorporating lots of compost and a dressing of bone meal. Gardenias love slightly acid soil, so if your soil is not acid enough, use lots of acid compost.
They enjoy an evenly moist soil that is not soggy, so water them year round, but particularly in spring and summer when the plant is flowering. Gardenias are heavy feeders and need to be fertilised on a regular basis with a balanced fertiliser. Pruning is sometimes necessary to help shape your plant or to keep it a smaller size. It is important that pruning be done after the plant has finished flowering, or you may cut off newly forming buds.
Propagation is by semi-hardwood cuttings which root easily in moist soil during the warm summer months; or by seed sown in spring and early summer.
Problems, Pests & Diseases:
Gardenias are susceptible to several pests, primarily sucking insects. Insect attacks are aggravated by lack of air circulation in small walled gardens and courtyards. The presence of insects may also be a sign that your plant is under stress, so ensure that it is well watered and correctly fertilised. Aphids, whitefly, spider mites, scale insects, mealy bug and sooty mould are common problems, which can be easily controlled by spraying with environmentally safe soap and oil sprays. Use a commercial sticker liker G-49 with your insecticide to help the poison stick to the glossy leaves.
Gardenias are very susceptible to nematodes, especially in sandy soils. Nematodes are mobile worm-like microscopic organisms which attack the roots of plants. They are easily recognisable, causing wart-like lumps on the roots about the size of a match head. Signs of nematodes are wilting and yellow leaves which persist even after fertilising. Potent chemicals are not suitable for use in the home garden, so rather sow marigolds near susceptible plants and dig them lightly into the soil when they have finished flowering. Khaki weed also works well to help control nematodes.
Gardenia flower buds may go brown, drop, or fail to open. This is fairly normal and occurs mainly because the plant tends to keep producing flower buds right through autumn, even though the plants growth is slowing down. The plant will often hold these buds right through winter and drop them in spring. Bud drop can also be caused by weevil or leaf hopper damage.
Yellow leaves can appear at any time of the year, but are particularly prevalent in spring. Yellowing is generally attributed to a magnesium deficiency and is treated with applications of Epsom salts (sulphate of magnesium). If your plant has been planted correctly, is fed regularly with a good all- purpose organic fertiliser, and is watered correctly, yellowing of the leaves should not become a problem. It is especially important to fertilise in spring when the weather warms up.
Gardenias are not poisonous. Like other plants, though, they should still be cultivated cautiously around small children, as plant parts may present choking hazards. Sensitive or allergic individuals may also experience a reaction to contact with the plant, so it is a good idea to wear gloves when working extensively with a gardenia.