Hop pruning is the removal of the first shoots in the spring prior to training. The primary reasons for pruning include disease management (removal of systemically infected shoots) and to ensure uniform shoots with higher yield potential for subsequent training.
Training is the selection of the best bines from regrowth after pruning and consists of the physical placement of the bine on strings (Fig 1).
Figure 1: Hop plants trained for the season.
Pruning can be accomplished by mowing or cutting 3-4 weeks before you expect to train the plants (smaller acreages/plantings can be pruned using a grass trimmer with a blade attachment). When shoots re-emerge, they will be more even in vigour and age. Pruning also removes ‘bull shoots’ which have longer internodes. Longer internodes on shoots ultimately translate into less branching on mature plants which in turn produce lower yields.
In Ontario and eastern North America, it is best to schedule your pruning and training practices based on experience in your growing zone and the cultivars you are growing. This means keeping good records each year of environmental conditions, dates of shoot emergence for each cultivar and corresponding harvest dates and yields. However, using the average frost free days for Ontario can provide a general guide for timing your pruning and training activities.
On the Climate Zone Map of Ontario (Fig 2), locate your growing area and use the corresponding table Target Dates for Pruning and Training Hops in Ontario (Table 1) to estimate the earliest possible pruning and training dates for your hop yard.
Figure 2: Climate Zone Map of Ontario (1976-2005). Source: Weather Innovations Incorporated (Available: www.omafra.gov.on.ca/english/crops/facts/climzoneveg.htm).
Table 1: Target Dates for Pruning and Training Hops in Ontario
|Pruning (earliest)||2016 Training Date (earliest)|
|A||Last week of March/First week of April||April 25|
|B||Last week of March/First week of April||April 30|
|C||First week of April||May 3|
|D||Second week of April||May 11|
|E||Last week of April||May 17|
Considerations: the dates provided in the chart are considered the earliest dates for management based on average frost free dates in those locations. Seasonal environmental and field conditions will always dictate maturity of plants and may permit or prevent you from actually performing the activities on or around the dates listed in the table.
Cautions: although the dates shown are based on historical weather information in Ontario, late spring frost episodes that took place 2-4 weeks after the average last frost free date in 2013 and 2015 caused considerable damage to the trained hop crop.
When scheduling spring activities, consider pruning weaker cultivars first (many times these are aroma varieties) to allow maximum time for re-growth; however some vigorous cultivars like Cascade could also be pruned early. The difficulty is learning how to optimize the timing of your pruning activities to avoid disease windows while at the same time pruning as early as possible (without the risk of frost damage) to maximize time for vegetative growth of plants to optimize yields. Keeping good, site specific, records is key!