To maximise the effectiveness of light interception by vine canopies

• Present a large canopy surface to the sun
• Encourage early development of that canopy in the spring
• Avoid inter-row shading by having a maximum ratio of canopy height to alley width of 1:1

To reduce canopy shading, particularly in the cluster/renewal zone

• In highly shaded leaves, the rate of respiration outstrips that of photosynthesis, so the leaf consumes rather than produces energy
• Shade reduces the viability and success of floral initiation in dormant buds, thus causing an imbalance between leaf area and fruit weight leading to Smart’s vegetative cycle.
• Shaded flowers have lower rates of successful fertilisation and fruit set
• Shaded berries keep cooler and so do not ripen as well in cool climates
• Shaded fruit have lower quality flavours and colours, as some of the biochemical reactions that produce these are stimulated by sunlight
• Shaded fruit and leaves have far greater risks of contracting fungal diseases, especially powdery mildew and grey rot

To produce a uniform microclimate for fruit

A uniform microclimate leads to more synchronised ripening, which leads to a greater chance of picking at the optimum period.

To achieve an appropriate distribution of the products of photosynthesis

• Too much fruit and not enough leaves (over-cropping) will generate poor quality fruit and reduce vine vigour
• Too many leaves and not enough fruit will cause over-vigorous growth, which will also produce poor quality fruit.

To arrange the locations of individual organs in restricted zones in space

• This facilitates mechanisation, particularly in pruning, pesticide application and harvesting

The first step in canopy management is diagnosis