Leaf removal
Leaf removal is a viticultural practice involving the deliberate removal of leaves from the grapevine canopy, most commonly in the fruiting zone around the grape clusters. It is used to modify the vine’s canopy microclimate in order to influence fruit exposure, disease pressure and grape composition, and is a central tool in modern canopy management.[1]
Purpose and principles
The primary objective of leaf removal is to improve light penetration and air circulation around the grape clusters. By reducing shading and humidity, the practice can lower the risk of fungal diseases and alter the balance between vegetative growth and fruit development.[2]
Leaf removal affects the vine’s microclimate rather than its overall vigour, making it distinct from more severe canopy interventions such as shoot thinning or hedging.
Timing of leaf removal
The effects of leaf removal depend strongly on timing. Early leaf removal, carried out before or shortly after flowering, can reduce fruit set and berry size, leading to lower yields and looser clusters.[3] Later leaf removal, typically around veraison, has less influence on yield but still improves cluster exposure and disease control.
Poorly timed or excessive leaf removal may increase the risk of sunburn, particularly in warm climates or during heatwaves.
Effects on grape composition
Increased exposure to sunlight resulting from leaf removal can enhance the accumulation of colour compounds and influence phenolic maturity in red grape varieties. It may also affect the degradation of methoxypyrazines, reducing herbaceous aromas in varieties such as Cabernet Sauvignon.[4]
In white varieties, leaf removal can modify aroma development and acidity retention, though outcomes vary widely depending on climate and site conditions.
Disease management
Leaf removal is widely used as a non-chemical strategy for controlling diseases such as powdery mildew and botrytis. Improved airflow and faster drying of clusters reduce the environmental conditions favourable to fungal growth.[5]
In regions with high disease pressure, leaf removal is often combined with other canopy practices as part of an integrated vineyard management strategy.
Methods and extent
Leaf removal may be performed manually or mechanically. Manual removal allows precise control over the number and position of leaves removed, while mechanical systems are more efficient in large-scale vineyards but offer less selectivity.[6]
The extent of removal varies by region and grape variety, ranging from partial removal on the morning-sun side of the row to more extensive exposure in cool or humid climates.
Risks and limitations
While leaf removal can deliver significant benefits, excessive exposure may lead to berry sunburn, reduced aroma intensity or imbalances in sugar and acid development. These risks are particularly acute in warm climates and under drought conditions.[7]
Effective leaf removal therefore requires site-specific adjustment based on climate, variety and seasonal conditions.
See also
References
- ↑ Jancis Robinson, Oxford Companion to Wine, Oxford University Press, 17 Sept. 2015. ISBN 9780198705383.
- ↑ Smart & Robinson, Sunlight into Wine, Winetitles, 1991, ISBN 978-1875130033.
- ↑ Markus Keller, The Science of Grapevines: Anatomy and Physiology, Academic Press Inc, 19 Jan. 2015. ISBN 9780124199873.
- ↑ PhD Jackson, Ronald S., Wine Science: Principles and Applications, Academic Press Inc, 14 April 2020. ISBN 9780128161180.
- ↑ OIV, “Canopy and leaf management”.
- ↑ UC Davis, “Leaf removal timing and effects”.
- ↑ AWRI, “Leaf removal and disease control”.