Optimal timing for basal leaf and lateral shoot removal

 Article written by Madeline Wimmer, UMN Extension Fruit Production Educator

Image: A grape shoot node anatomy includes the region with a developing bud (B), lateral shoot (Lat), leaf (L), and tendril (T). 

Basal (i.e., around the cluster zone) leaf and lateral shoot removal is a simple, low-input practice that removes leaves and lateral shoots from the lower nodes near developing clusters. This can enhance fruit quality by increasing air flow and direct sunlight exposure on developing fruit clusters and basal buds, which give way to shoots and clusters the following growing season. Basal leaf and lateral shoot removal also increases spray penetration for products like fungicides, etc.


The timing in which basal leaf removal is completed can make an impact. Leaf thinning has traditionally been done after fruits have set, with some research in Michigan looking at the benefits of pre-bloom thinning (see end of article for more information).


Research done in the Upper Midwest on post-bloom thinning has shown a positive impact on fruit quality when basal leaf removal is done pre-veraison around E-L stage 29. This is about two weeks post-fruit set when berries are peppercorn in size (1).


This specific stage of basal leaf removal has been shown to cause an increase in total phenolic content for red and white wine grapes, as well as improved wine color stability. Other research has shown decreased titratable acidity and a reduction in vegetative flavors with increased cluster exposure (2) . This is in part due to the increase in berry temperature that occurs with more sunlight exposure.

Best practices post fruit set

Basal leaf removal

• Basal leaf and lateral shoot removal involves removing 1-3 leaves per shoot in the cluster zone and taking out any lateral shoots growing from the first three node positions.

• The number of basal leaves removed depends on which direction a vineyard row side is oriented, how much canopy length each vine has, and the general vigor of the vines.  

• Grapevines planted in rows that run east to west have a north and south side facing canopy. In this situation it is often possible to remove more leaves on the canopy northside where less intense sun exposure occurs. 

• Vineyard rows that run north to south have canopies with east and west side exposure and can have a similar number of leaves removed from each canopy side.

Basal lateral shoot removal

• For high-vigor vineyards experiencing extensive basal lateral shoot growth, removal when lateral shoots are first emerging can be a quick way to address the issue. 

• For VSP vines grown with catchwires, lateral shoots can sometimes be tucked into the catchwire “basket”, but this can still limit airflow in already-dense canopies.

• Lateral shoots emerging above the fruiting zone can usually be retained. 

Pre-bloom leaf removal

Research done more recently in Michigan frames leaf removal as a “cornerstone of precision grape production” stating that higher fruit quality is essential for establishing a good reputation for wine, especially in regions with shorter growing seasons. Their research focused on early leaf removal, looking at pre-bloom selective removal (10-15 days before bloom) for the purpose of altering carbon (energy) allocations and hormonal signalling to reduce berry set and promote looser clusters.

Why would this be desirable? It changes how humid the conditions are between the berries and prevents water from being trapped, which can reduce the likelihood of infection of diseases like Botrytis and sour rot. This research additionally saw an increase in flavonoid biosynthesis (including compounds with antioxidant activity including anthocyanins), skin thickness, and improved color development with early leaf removal. Because it creates looser clusters with less fruit set, there is potential for some vineyards to reduce the need for cluster thinning when using this technique.

To learn more about how to leaf thin, check out this video with John Thull, UMN Horticultural Research Center Vineyard Manager:

Video: Leaf pulling VSP and HC

References:

1. Jacob Scharfetter, Beth Ann Workmaster, Amaya Atucha. Preveraison Leaf Removal Changes Fruit Zone Microclimate and Phenolics in Cold Climate Interspecific Hybrid Grapes Grown under Cool Climate Conditions. Am J Enol Vitic. 2019 70:297-307 ; DOI: 10.5344/ajev.2019.18052

2. Jean Riesterer-Loper, Beth Ann Workmaster, Amaya Atucha.Restricted accessImpact of Fruit Zone Sunlight Exposure on Ripening Profiles of Cold Climate Interspecific Hybrid Winegrapes. Am J Enol Vitic. 2019 70:286-296 ; DOI: 10.5344/ajev.2019.18080

3. Paolo Sabbatini, Michigan State University Extension, Department of Horticulture. Cutting to the core: Michigan State research leads a canopy innovation in cool-climate viticulture. 2025.