Shoot thinning is a canopy management practice that involves removing shoots in the grapevine canopy to reduce shoot density and help balance vegetative and reproductive growth.
Potential benefits of shoot thinning:
- Improved air circulation
- Improved sunlight penetration
- Reduction of disease pressure
- Increased spray penetration
*shoot thinning and positioning not only affects the current season’s growth, but it has an impact on the productivity in the following year as sunlight encourages the development of fruitfulness in the buds for next year’s crop
Timing
The ideal time for shoot thinning is when the shoots are between 6-12 inches long. Shoot thinning after the shoots reach 12 inches in length may be more difficult due to lignification of the shoot base; pruning shears should be used at this time to reduce injury to the vine.
How much to shoot thin
The preferred shoot density for different types of varieties is listed below:
Hybrids: 4-6 shoots per foot
Vinifera: 3-5 shoots per foot
Native or Labrusca: < 15 shoots per foot
Figure 1. Optimal shoot density (~4 shoots per linear foot of cordon) in Merlot; Photo by Cain Hickey
Tips for deciding which shoots to keep
Health: Shoots with a pencil-width diameter, good internode lengths that are otherwise healthy-looking are preferred over weak, diseased shoots
Positioning: In a spur-pruned vines, priority should be given to fruitful primary shoots from count nodes 1-2 on each spur
For more information:
Best Viticulture Practices: Shoot Thinning: https://ohiograpeweb.cfaes.ohio-state.edu/blog/may-21-2022-1031am/best-viticulture-practices-shoot-thinning
Canopy Management- Shoot Thinning and Positioning: https://extension.umd.edu/resource/canopy-management-shoot-thinning-and-positioning