Do I Need to Cover Gardenias When It Freezes?

Gardenias

• Classed in the family Rubiaceae, genus Gardenia, gardenias have waxy white flowers, 1 to 5 inches wide, that grow among shiny, dark green, oval-shaped leaves. Some cultivars have yellow petals with purple mottling. All possess the unique aroma of jasmine, vanilla and nutmeg followed by bitter, yellow-red berries. In Southern zones, they are used as hedges, screens, borders and ground cover.

  Cultivated in China for millennia, gardenias spread to England in 1761 and were named after South Carolina botanist Dr. Alexander Garden. They are prized as cut flowers and popular as corsages, as boutonnieres and in wedding bouquets.

Hardiness

• Gardenias are semitropical; they grow best in mild, humid climates. They will drop flower buds when temperatures cool quickly and they can sustain severe injury in below-freezing weather.

  Gardenia jasminoides, an indoor species in temperate zones, grows outdoors from zone 8 to zone 10, including Georgia, Florida and Southern California. It is susceptible to frost; you must cover it to protect it when temperatures drop.

  Frost-tolerant cultivars for zones 7 to 10 include a variety of jasminoides called Kleim's Hardy that is also disease-resistant, Frost Proof and Chuck Hayes, which have large double blooms and grow outdoors in temperatures to 10 degrees below zero Fahrenheit from Oregon to Washington, Idaho and Northern California.

Growing

• Gardenias thrive in sun or partial shade in hot climates in acidic soil between 5.0 and 6.5 pH. Don't plant them near concrete walks, patios or house foundations, which encourage alkaline conditions. Gardenias planted in alkaline soil will be weaker and less able to survive a frost. They need regular fertilizing with acid-loving-plant formulas and annual foliar spraying with iron to gain optimum health.

Options

• Gardenias thrive in 68- to 74-degree Fahrenheit daytime temperatures and 60-degree Fahrenheit evening temperatures. If you live in colder zones, grow gardenias in pots outdoors in the summers and bring them inside before the first frost.

  If your soil is alkaline (higher than 6.5 pH), containers allow you to control the soil and growing conditions. You can move them around outside to get the sunshine they need and whisk them indoors before the first frost. Gardenias do not like to be transplanted, though, so pot-growing is a way to put them in ideal locations, protect them from harsh weather and enjoy their beautiful flowers and fragrance.