Sour cherries require careful pruning to maintain their compact crowns and ensure consistent fertility. The best time to prune sour cherry trees is immediately after harvesting in the summer. This guide explains the differences in growth habits among sour cherry varieties and provides step-by-step instructions for effective pruning.
Understanding Growth Types in Sour Cherries
Sour cherries differ significantly from sweet cherries in growth and fruiting behavior. While sweet cherries produce blossoms on older wood, most sour cherry varieties bear fruit primarily on one-year-old wood—branches that grew during the previous year. Older long shoots often become barren and produce only short new growth with minimal bud production.
Some sour cherry varieties, like the popular ‘Schattenmorelle,’ belong to the “Morello type” (Prunus cerasus var. acida). These trees require heavier pruning due to their tendency to produce sparse bouquet shoots—short fruiting wood with multiple flower buds. Other varieties, like ‘Koröser Weichsel’ and ‘Heimanns Rubinweichsel,’ fall under the “Sweet Weichsel type,” which demands lighter pruning as they fruit well on older wood and develop dense bouquet shoots.
Key Pruning Guidelines for Sour Cherries
1. Pruning Morello-Type Sour Cherries
To maintain productivity in Morello-type sour cherries:
- Timing: Prune immediately after harvest. Early pruning encourages vigorous new fruiting shoots for the following year.
- Method: Remove about three-quarters of the long fruiting shoots, cutting them back to about a quarter of their original length. Ideally, prune just above a young side shoot to stimulate balanced growth.
- Additional Tips: Regularly thin out older, barren branches to improve light penetration and airflow within the crown. This reduces the risk of fungal diseases, such as Monilia tip blight. Always cut infected branches back to healthy wood.
2. Pruning Sweet Weichsel-Type Sour Cherries
For Sweet Weichsel cherries:
- Timing: Prune after harvest, focusing on removing weak or inward-growing shoots to maintain an airy crown.
- Method: Rejuvenate older fruiting wood (more than three years old) by cutting it back to a younger shoot.
- Considerations: These trees require less aggressive pruning as they fruit well on short, bud-rich bouquet shoots.
3. Handling Hybrid and Intermediate Varieties
Some sour cherries exhibit mixed growth characteristics. Varieties like ‘Ludwigs Frühe’ and ‘Schwäbische Weichsel’ don’t produce extensive long shoots but also lack dense bouquet shoots. For these:
- Thin the canopy to balance light and airflow.
- Prune individual branches to promote the development of new shoots and maintain a compact, productive crown.
Additional Tips for Successful Pruning
- Tools: Keep your pruning shears sharp to make clean cuts and prevent damage to the tree. Regular maintenance of your tools ensures precision and reduces the risk of disease spread.
- Disease Prevention: When pruning, remove all visibly diseased or damaged wood. For fungal infections like Monilia, cut back at least a hand’s breadth into healthy wood.
- Shaping: For a well-structured crown, remove excess or crossing branches and focus on creating a balanced canopy that allows sunlight to reach all parts of the tree.
Conclusion
Pruning sour cherry trees is an essential task for maintaining their health, productivity, and aesthetic appeal. By understanding the growth characteristics of your specific variety and applying the appropriate pruning techniques, you can enjoy bountiful harvests year after year. Whether you’re managing a robust Morello cherry or a graceful Sweet Weichsel, timely and skillful pruning will reward you with a thriving tree and delicious fruit.
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