Freeze Resistant Orchids

Types of Orchids

• Orchids are divided into two basic categories: Epiphyte orchids grow in trees and on other plants. Their roots do not grow in soil, but are exposed to the air. These roots have special tissues called "velamen," which absorb water from the air and hold it. They also draw in nutrients from the surrounding plant to nourish the orchid.

  Terrestrial orchids grow in soil and are not exposed to the air. Their roots function as other plants do, but they generally do not require much fertilizer. Give this type of orchid only weak solutions of fertilizer at half-strength. Most freeze-resistant varieties of orchid are terrestrial types. Wild terrestrial orchids, such as Cypripedium guttatum and Cypripedium passerinum, can even grow in Alaska, according to the U.S. Forest Service. These wild orchids do not transplant well and are generally protected by law to preserve their population in natural environments.

Cold Hardy Orchids

• Generally, it is the Cattleya, Laelia and Sophronitis varieties that are the most freeze resistant, according to the Orchid Society Council of Victoria. Many large-flowered Cattleya varieties cannot tolerate any degree of frost, however, so research the type carefully before exposing your orchid plant to frost conditions. Some varieties of Cattleya, such as the Cattleya intermedia can tolerate temperatures down to the mid-20s. Your local orchid society can offer advice on particular cultivars that can withstand cold conditions in your area.

Caring for Cold Hardy Orchids

• Cold-hardy orchids can tolerate frosts and many types even require cold temperatures for a time in order to produce blooms. Protect your cold-hardy plants by spreading a layer of chipped wood bark around plants to insulate the rhizomes under the ground when temperatures begin to drop below freezing. Withhold water and fertilizer until spring.

Freeze Damage to Orchids

• Frost damage on orchids will show as pitted marks or sunken areas. Discolored areas soon turn brown and die. Hard freezes will generally kill cold hardy orchids to the ground, but they re-emerge with new growth in the spring when temperatures start to climb.