Plum Tree Flower Damage

Cold Winter Weather

Unusually cold winter weather, as well as alternating spells of warm and cold weather, can kill dormant flower buds on both ornamental and fruit-bearing plum trees. Always plant plum cultivars that have proven hardy in your climate zone. Consult your local garden center or county extension service for advice on cultivars.

Plum flowers and buds are much less tolerant of cold temperatures once the tree breaks dormancy. Even a light frost causes flower damage, usually apparent as browning on the flowers. All flowers will be killed when the temperature drops below 28 or 29 degrees Fahrenheit. Minimize frost damage by planting the trees close to the house or on elevated areas, not at the bottom of a slope.

Plums are susceptible to infestations of thrips, such as the western flower thrip (Frankliniella occidentalis). Thrips are small insects that feed on flower pollen and pierce the leaves and flower petals to suck out the juices inside the tissue. Control thrip populations by clearing away all debris from around the tree in the fall, since these insects overwinter among fallen leaves. If the infestation is severe, consult with your local extension service for information on insecticides approved for use in your state.

In damp regions, such as the Pacific Northwest, plums may develop brown rot, a fungal disease that first infects the flowers and then moves to small branches. Reduce the chances of infection by planting your trees in sunny sites with good air circulation. Your garden center can recommend a fungicide, but be sure it's approved for use on food crops if you're growing fruit-bearing plums.