Hops are at various vegetative stages across the province depending on cultivar and location.  Leaf stripping (removal of lower leaves and laterals primarily for disease management) is well underway.  General recommendations suggest removing up to 1.5 m of leaves from the bottom of the bine.  However, age of plant and height of plant should be taken into consideration when scheduling date and extent (height) of leaf stripping in order to reduce impact on yield and resin content of cones and carbohydrate reserves in roots.

Historical studies have shown that removing leaves from the bine is less harmful to the plant then removing leaves from the laterals, in terms of yield loss, however both practices will decrease overall yield potential.  Resin content (and specifically alpha acids) also decrease as more leaf area is removed from the plant.

Plants up to 3 years of age should be allowed to grow higher and produce more foliage before stripping commences in order to overcome detrimental effects of leaf removal. Plants over 3 years old can typically withstand stripping at an earlier date or when the plant is shorter by drawing on carbohydrate reserves in the roots until it produces more leaf area for photosynthate generation later in the season.

References:

• Kisgeci, J.  1977.  The role of different leaves in hop yield and quality production.  Savremena Poljoprivreda 25:41-49.
• Mahaffee, W.F., Pethybridge, S.J., and D.H. Gent (eds.).  2009.  Compendium of Hop Diseases and Pests. The American Phytopathological Society, St. Paul.
• Williams, I.H.  1962. The effect of stripping and cutting upon the carbohydrate status and yield of young hops.  Annual Report, Department of Hop Research, Wye College, p. 59-68.