The glossy dark green leaves and fragrant milky white flowers of the gardenia plant make it an irresistible plant to grow. Usually sold in bloom or bud, the intoxicating fragrance entices us to make it a must have plant but gardenia can be finicky and a challenge to grow in indoors. In fact, some treat it as a disposable plant and discard it after blooming.
Gardenia (Cape jasmine) requires loose well-drained, acidic (ph4.5-6.2) soil, bright indoor sun 6-8 hrs and dappled shade (morning sun) when outdoors in the summer. It prefers high humidity and moist but not soggy soil. Feed it with a 1/2 strength acid fertilizer every 2-4 weeks from March-October.
For winter care: Provide a cool bright location, humidity and keep away from heating vents. Do not fertilize and water less by allowing the top 1-2 inches to dry before watering again.
Blooming: Gardenias require an even temperature of 62-63 F and high humidity during bud formation. To increase humidity place plant in a water pebble tray or close to a humidifier. When the buds are formed, provide consistent cool nights (58-60F) and warm days (70-75F). A 10-15 degree temperature differential is needed to keep the buds from dropping off (bud blast). Opened flowers should last 3-8 days and bruise easily when touched.
Prune after the blooming cycle has ended, or when the plant is actively growing and needs a trim. Don’t prune during winter.
Propagation: Take 3-4 inch semi-woody tip cutting from a non-flowering shoot in early spring. Remove lower leaves, dip in rooting hormone and insert cutting in moist peat, vermiculite mix. It should root in 4-6 weeks.
Gardenias attract a number of insects: aphids, mealy bugs, scale, red spider mites and thrips. They are also susceptible to root rot, bud drop and yellow leaves.
In the south and west coastal areas (zone 7b), semi-tropical gardenias are grown outdoors as evergreen shrubs. Varieties can differ in size, growth habit and blooming season. ‘Mystery’ a California favorite gets up to 8′ tall and produces large double flowers.