Updated/Fact-Chacked on July 28, 2021 by John
People often return from holiday with the idea of growing a Gardenia as a houseplant, after seeing larger versions growing outdoors in hotter climates. The plant’s heady perfume from pure white flowers seems very appealing, yet the results can often be disappointing because if conditions aren’t perfect the plants look like disaster areas with yellow drooping leaves, brown rotting and misshapen flowers and a general air of dejection.
Gardenias prefer regular substantial watering, but they also need moderately well-drained soils with plenty of organic materials worked in before planting – so sit the plant on a tray of moist gravel in a greenhouse area that faces east. Because they are related to the Rhododendrons and Azaleas, these plants do best in an acidic soil. The root system is shallow and sensitive, so use a lime-free compost and a fertiliser intended for lime-hating plants. Water them with rain water if possible, or use boiled and/or filtered water to remove the carbonates. Pinching out the tips while the plant is dormant will cause the plant to become bushier. Pinching usually promote heavier blooms the following year.
Finally, gardenias are sensitive to high salt levels in the soil which results from using hard water and fertilisers when grown in a greenhouse, they need to have their soil changed regularly, but on a day to day basis to prevent salt build-ups, do not over-fertilise and periodically leach the soil with rain water to wash out excess salts. Gardenia plants should be fed from spring to autumn with specialist Azalea and Camellia food.
Greenhouse gardening gardenia photograph by Terra 2055, used under a creative commons attribution licence
John Green is a 46-year-old graphic designer living in Durham. John is RHS level 3 certified and owns an allotment in Durham.