Gardening for You: Perfect storm leads to early bud break in peaches

Today’s column is a Q&A in response to a question from a Lubbock A-J reader about early bud break in peaches.

Buds are beginning to swell and show the pink blossom color of this peach tree. Due to a perfect storm of plant hormones and warm January temperatures buds are breaking dormancy.
Buds are beginning to swell and show the pink blossom color of this peach tree. Due to a perfect storm of plant hormones and warm January temperatures buds are breaking dormancy.

Q. Lubbock A-J reader Patsy D. of Lubbock has peach trees with buds that are swelling and showing color. She is concerned that this is too early and wonders what is going on with her trees.

A. Early bud break is the result of a “perfect storm” of a tree’s physiology and the temperature. Peach trees showing early stages of budding out in January in Lubbock is definitely cause for concern.

Peach trees bear fruit once each year. Buds are initiated in late summer and following a period of dormancy over the winter, will break (open) when physiological, hormonal, and environmental conditions have been met. Over the winter, growth-inhibiting hormones decrease with a concomitant increase in growth-promoting hormones; growth-inhibiting hormones keep the buds tight and dormant. The hormonal changes result from complex chemical reactions that occur during a process known as the "chilling requirement."

The chilling requirement is the number of hours of between 32°F and 40°F required by a tree to resume growth following a period of dormancy. The chilling requirement is the accumulation of the total number of cold hours and it is during the chilling period that the hormonal changes happen.

Every stone (peach, almond, apricot) and pome (apple, pear) tree are genetically programmed with specific chill hours. Examples of peach varieties with few chill hours are ‘Nova Spy’, 100 and ‘Dorsett Delicious’, 300 hours; while the variety ‘Elberta’ has 800-950 hours. Buds of ‘Elberta’ will stay dormant much longer than ‘Nova Spy’.

Peach varieties grown in our region should have a chill requirement of 800 hours. Those with low chill requirements (450 hours or fewer) will have the chill requirement satisfied in January and bloom early; these should be grown only in South Texas.

A variety with a low chill requirement is likely the reason for the early bud break in Patsy’s fruit trees.

Two factors led to this perfect storm: In November and December there were 56 days with some hours of 40°F and below, accumulating approximately 350 chill hours (wunderground.com). January saw an abrupt shift to abnormally warm temperatures.

Average normal daily temperatures in January for Lubbock are day highs of 55°F and 27°F nights but there were at least 15 consecutive days that were 20 degrees above normal, record highs of 77°F with no freezes. It was during these months that varieties with low chill requirement met their chill hours and with the January extended favorable temperatures, broke dormancy.

Buds that have leafed out or begun flowering are subject to freeze damage. Since there are still three months before our usual last freeze the end of April, these buds can be expected to not last through the winter. Unfortunately, these trees will not set fruit this summer.

Advice to the gardener: choose varieties that have a high-chill requirement.

Ellen Peffley taught horticulture at the college level for 28 years, 25 of those at Texas Tech, during which time she developed two onion varieties. She is now the sole proprietor of From the Garden, a market garden farmette. You can email her at gardens@suddenlink.net

This article originally appeared on Lubbock Avalanche-Journal: Gardening for You: Perfect storm leads to early bud break in peaches