Tracking spring bud development in fruit crops this year

Image: Grape bud development takes time from buds initially exiting dormancy until the first leaves and clusters are noticeable. 

    Perennial fruit crops require a period of dormancy to produce fruit each year. After fall acclimation a period of deeper dormancy, known as endodormancy, begins within a plant until it completes its chilling requirements (refer to the article, “Understanding dormancy and chilling hours in perennial fruit crops” for a detailed explanation). Once it has accumulated enough chilling hours, the plant goes from endodormancy to ecodormancy stage. This could be viewed as a transitional phase where dormancy is maintained by external environmental conditions rather than internal physiological factors. Eventually the plant exits dormancy and begins bud development to produce vegetation and/or flowers.


    As bud development begins, the rate at which buds develop relates largely to ambient temperatures, and is influenced by soil temperature and moisture, along with various aspects about a particular plant species’ or variety’s physiology. Generally, buds develop at a faster rate when temperatures are warm, and slow down with cooler temperatures. Additionally, as buds progress through their developmental stages, they become more vulnerable to frost damage, with their critical temperature (the threshold at which damage occurs) increasing as development progresses. This is because, as cell division and expansion occur, these tissues contain more water and are less resilient to external cold conditions. For example, apple buds at the beginning of bud development (i.e., silver tip phase) are less sensitive to cold damage than when leaf tips begin to emerge from the developing bud (i.e., half-inch green).


    Dormant buds vary between fruit crops. In some fruit crops, separate buds produce either vegetative growth or flowers, while in others, a single bud may contain both flower and vegetative structures. For example, in grapes, buds that contain flowers will always develop alongside a shoot, whereas in peaches, blossoms emerge separately from vegetative growth. While different fruit crops have unique terminology for bud development stages, the underlying physiological process remains largely similar: buds remain tightly closed during dormancy; as they begin development, bud scales gradually separate, eventually revealing emerging leaves and/or floral structures until full leaf-out and bloom.


    Taking notes on bud development and bloom times can help you keep track of variations from year to year, and keep you informed this year to anticipate potential impacts of spring frosts. 

The following are resources to help you track bud development for your fruit crops this spring:

Tree fruits: Critical spring temperatures for tree fruit bud development phases (Michigan State University)

Grapes: Major growth stages (E-L Chart)

Blueberries: Critical spring temperatures (Michigan State University) and Growth stages (Michigan State University)


For more information on mitigating spring frost damage for perennial fruit crops, check out the article, “Escaping spring frost in the Upper Midwest.”

Finally, feel welcome to email me directly (wimm0035@umn.edu) if you would like to share pictures or ask questions related to bud development this spring.

This article was written by Madeline Wimmer, UMN Extension educator- Fruit Production.