Gardenia Bushes in Winter

Gardenias

• Gardenias thrive in moist but well-drained rich, acidic soil, ideally with a pH between 5.0 and 5.5. The most common backyard gardenia species, Gardenia jasminoides, is native to China and Japan. There are many cultivars, ranging from 2-to-8 feet in height, some hardier than others. Gardenias are hardy in USDA zone 9, but some thrive to zone 7, tolerating cold as low as zero-to-10 degrees Fahrenheit. In cooler climates, grow gardenias in full sun but in protected areas adjacent to the house for extra winter cold protection. In hotter climates, provide filtered shade. Nighttime temperatures are critical for flower production. Healthy plants growing at 60-to-62 degrees Fahrenheit will bloom steadily.

Wintering Gardenias Indoors

• Confined indoors in low light and hot, dry air, even healthy potted gardenias will soon decline, dropping flower buds and, eventually, yellowing leaves. They thrive with bright light, moderate temperatures and adequate humidity. Overwinter gardenias in a south- or west-facing window that provides a half-day of sun. Place the gardenia pot on a tray of pebbles partly filled with water; make sure the pot doesn’t touch the water. Daytime temperatures of 70-to-75 degrees Fahrenheit and nighttime temperatures about 60 degrees are ideal for healthy growth and flowering. Fertilize monthly with acid plant fertilizer, and occasionally flush pots with water to prevent salt buildup that can burn roots.

Wintering Gardenias Outdoors

• Gardenias are cold-sensitive evergreens. Growing them outdoors where they are hardy is the easiest way to provide winter care. According to Hawaii Cooperative Extension, gardenias are frost hardy to about 20 degrees Fahrenheit. In areas of borderline hardiness, they may freeze back to the ground during unexpected cold snaps yet grow again from roots come spring. Don’t fertilize or prune outdoor gardenias in autumn, because both actions will encourage tender new growth particularly vulnerable to winter cold.

Winter-Hardy Gardenias

• Some newer cultivars are much hardier than gardenias generally – good choices for gardeners in colder climates. Grow them outdoors to zone 7; where it’s colder, bring them indoors for winter. Chuck Hayes is a rounded 4-foot shrub with sweetly perfumed double flowers with plump petals. Aside from living up to its name, the more upright Frost Proof also features double flowers -- large ones with narrow petals. Kleim’s Hardy is smaller and rounded, forming mounds 2-to-3 feet tall. It has six-petaled single flowers with yellow stamens.