How to Winterize a Gardenia Bush
The heady scent of a gardenia could be just the thing you need during the winter months when the sky is gray and you are cooped up indoors. While gardenia shrubs (Gardenia jasminoides) are warmth-loving plants growing in USDA hardiness zones 7 to 11, gardeners who live in a colder climate can overwinter them, by growing them in containers and moving them indoors.
However, gardenias are fussy plants, so you need to provide just the right indoor environment.
Gardenias, also called cape jasmine, are evergreen shrubs with dark green, glossy leaves and astoundingly fragrant flowers. The bloom period for gardenias ranges from late spring to mid-summer, depending on the variety.
Gardenias are acid-loving plants. If you grow gardenias in a container, add aluminum sulfate or sulfur to the potting soil.
Gardenias have precise growing requirements. They prefer acidic soil with a pH below 6.0. They appreciate well-draining soil with plenty of organic matter, such as compost. They hate to have their roots disturbed, so mulch the plants to control weeds rather than use a hoe or other tool that might dig into the soil.
While gardenias can handle full sun, they appreciate some partial shade. They benefit from afternoon shade when the sun is its hottest.
Gardenias and Cold Hardiness
If you live in the warmer areas of a gardenia's growing zones, the plant will flower throughout the year if the temperature remains above 60°F. Most varieties are cold hardy down to zone 8, but some cultivars can handle chillier temps, so be sure you know your variety.
One somewhat frost-proof gardenia is called Frost Proof (Gardenia jasminoides 'Frostproof’). Then there is Kleim’s Hardy (Gardenia jasminoides 'Kleim's Hardy'). Both are so named because they are considered cold hardy to zone 7 and can handle average winter temps of between 0 to 10°F. Although they may experience some damage to leaves at these temps, their roots will be fine.
However, if you live in colder zones or have more tender varieties of gardenia bushes, you need to overwinter them during the colder months.
In a zone colder than the gardenia can handle, grow it in a pot and bring it indoors for winter. Gardenias are famously finicky plants, and there is no guarantee they will acclimate to an indoor climate with any finesse—but these tips might help you get them through the winter doldrums:
- Prune gardenias immediately after flowering and avoid pruning them in the late summer, which could stimulate new growth before the cold weather sets in.
- Similarly, avoid fertilizing gardenias in the fall, which also stimulates new, tender growth.
- Bring gardenias indoors before the first frost to avoid cold damage.
- Locate the plant near a southern-facing window where it will get bright light.
- Ensure moderate temperatures and regular watering, using room-temperature water. Never allow your gardenia to dry out.
- Provide humidity. Gardenias won't thrive if your home is too warm and dry. Ideally, place a humidifier near the plant and leave it on. If that’s not feasible, give it a shower every so often, which also washes off a common pest of houseplants, spider mites.
- Grow gardenias in containers that can be brought indoors during extremely cold winters.
I garden in the Pacific North west, previously Hawaii where I had an avocado orchard. I have a Master Gardeners certificate here in Eugene, Oregon.