Frost and Pear Trees

Temperature

• Pear blossoms can withstand temperatures of 24 degrees as long as they are in a tight cluster, but as they begin to open and bloom, they become more susceptible to cold. Blossoms in the first bloom stage, for instance, require temperatures of 29 degrees or higher to remain damage-free. In the post-bloom stage, the blossoms require temperatures of 30 degrees or higher.

Damage

• When pear blossoms are damaged by frost, the injured tissue turns dark, becoming blackish-brown with time. If the blossom's pistil (the center part of the blossom) is damaged, it will turn brown, indicating the flower is dead and will not develop to become fruit. This does not necessarily result in lower crop yield. Pears and other large-fruited fruit trees can suffer as much as 75 percent flower loss and still produce a decent yield.

Protection

• Covering the pear trees when a heavy frost is expected can help to prevent injury to the tree's blossoms. This will protect the trees from direct contact with frost. Cover the trees with cloth, such as cheesecloth or bed sheets. Commercial orchards heat their orchards during bloom time, but this is not a practical method for home gardens.

Hardy Varieties

• Some varieties of pear are more cold hardy than others. These varieties tend to blossom later. Examples of cold hardy pear tree varieties include Summer Crisp, Parker, Luscious, Gourmet, Williams, Bon Chretien and Onward. Invincible, also known as Delwinor, is a hardy pear tree that flowers twice, with the second flush of blooms often missing the latest frosts.