Gardenia Winter Hardiness

USDA Zone

• Common gardenias are hardy to 10 degrees Fahrenheit and can be grown in U.S. Department of Agriculture hardiness zones 8 through 10, and in zone 7b. Protect them from dry winter winds and hard freezes in areas where they’re marginally hardy. Gardenias may die back to the ground when temperatures drop to zero degrees Fahrenheit, but should regenerate in the spring.

Hardy Varieties

• According to horticulturists at Missouri Botanical Garden Kemper Center For Home Gardening, the Shooting Star gardenia cultivar is the hardiest of the common gardenias and can be grown throughout USDA zones 7 through 10. When growing this cultivar in marginal areas, place it in a sheltered location and provide it with an organic root mulch. The Chuck Hayes cultivar is an extra hardy type and Kleim’s Hardy also exhibits cold hardiness. These cultivars, along with Frost Proof, can be grown throughout USDA zone 7.

Location

• Gardenias can’t absorb much water from the soil when it’s cold or frozen, but they can continue to lose water through their leaves when exposed to dry, winter winds and bright sun. Plant susceptible gardenias on the north, northeast or east side of a building to protect them from these conditions. Siting shrubs in these locations will also delay spring growth, which will help protect shrubs from late spring frosts. Don’t plant gardenias in low spots where frost is more likely to form.

Protection

• Several steps can be taken to minimize damage to your gardenia shrubs over the winter. Provide shrubs with a 3-inch layer of mulch to help keep the soil warm and retain moisture. Build a windbreak by attaching burlap to a wooden frame on two sides of your shrub, or build a frame over the shrub and cover it with burlap before sealing to the ground. Don’t fertilize gardenias late in the summer or fall because it will stimulate new growth that doesn’t have a chance to harden off for winter. Water your gardenias before a hard freeze because wet soil absorbs more of the sun’s heat than dry soil does, and will help keep your shrubs warmer.

Pruning

• Don’t be too quick to prune your gardenia shrub after a freeze, even if it looks dead. Damage can’t be assessed until spring, when new growth begins, and dead branches and leaves will continue to protect living tissue from additional damage. If you scrape a branch with a knife and see a green layer underneath, the branch should eventually recover.