College of Agriculture & Natural Resources Department of Horticulture

Some Cherry Pruning Considerations and Concepts for Discussion

Dr. Gregory A. Lang, WSU/IAREC Stone Fruit Field Day

June 6, 2000

• Good pruning is a combination of tradition, art, and science, probably in that order.

• The introduction of new plant factors – e.g., dwarf stocks, unique bearing habit – place more emphasis on art and science than traditional success.

• Why prune a fruit tree? 1) Contain tree in its allotted orchard space, 2) Remove unhealthy or poorly-placed wood, 3) Ensure light distribution through out canopy, 4) Balance the future crop load (“resource sinks”) with the future leaf area (“resource synthesis”).

• In cherries, a significant amount of spring fruit (and shoot) growth is dependent on stored resources (synthesized carbohydrates, applied nitrogen) from the previous year’s growing season. Jake Gutzwiler’s research has shown that in spring, new shoots out-compete developing fruits for stored resources. As new shoots mature, photosynthesis from leaves near fruit become more important than stored resources for the final stages of fruit development.

• Heavy cropping removes a lot of resources from a tree; these must be replenished via greater opportunity for resource synthesis by leaves (e.g., more leaves) and/or via greater resource storage by higher fertilization (foliar, maybe ground applications).

• The new shoot growth that occurs this year will provide: in 2000, photosynthesis mostly for self-growth and winter storage reserves; in 2001, sites for new flower buds to form microscopically plus photosynthesis to support direct growth of older fruiting sites; and in 2002, actual fruiting sites plus spur leaves to support those fruit. Thus, the current 2000 crop was determined to a large extent by the new growth that occurred in 1998 (and pruning decisions that were made then).

• Other ongoing research – Dormant heading cuts help balance the propensity for heavy crop loads in trees on Gisela® rootstocks by 1) possible removal of existing flower buds to affect this year’s crop, 2) stimulation of new shoots for eventual resource synthesis to affect this year’s crop, and/or 3) possible inhibition of flower bud formation on year-old wood, or flower bud abortion on older existing spurs, to affect the size of next year’s crop.

For more information, please refer to these recent Publications

(Available links generally refer to the abstract from the article. Access to full text of the article may require membership and/or subscription. GoodFruit Grower articles are available online for subscribers by registering at www.goodfruit.com)

• Gutzwiler, J. and G.A. Lang. 2001. Sweet cherry crop load and vigor management on Gisela^® rootstocks. Acta Horticulturae 557:321-325.

• Lang, G.A. 2001. Intensive sweet cherry orchard systems - rootstocks, vigor, precocity, productivity, and management. Compact Fruit Tree 34(1):23-26.

• Whiting, M.D. and G.A. Lang. 2001. Sweet cherry photosynthesis, crop load, and fruit quality relationships. Fruit Grower News 40(11):42-46.

• Lang, G.A. and D.R. Ophardt. 2000. Intensive crop regulation strategies in sweet cherries. Acta Horticulturae 514:227-234.

• Guimond, C.M, G.A. Lang, and P.K. Andrews. 1998. Timing and severity of summer pruning affects flower initiation and shoot regrowth in sweet cherry. HortScience 33:647-649.

• Lang, G.A. 1998. High density orchards and intensive crop regulation. Good Fruit Grower 49(16):45-47.

• Maib, K.M., P.K. Andrews, G.A. Lang, and K.D. Mullinix (eds). 1996. Tree Fruit Physiology: Growth and Development. Good Fruit Grower Press, Yakima. 165 pp.