Trunk length

Increasing trunk length has the following effects:

• Decreasing ground frost risk
• Decreasing the beneficial effects of convected heat from the soil. Chaptal (1943) found that the average difference between maximum temperatures at 20 cm and 2 m above the soil was 1.6°C
• Easing of manual operations. The optimum height for workers is 1.1 – 1.4m
• Easing of weed control and mechanical harvesting
• Increased starch storage, leading to more regular yields and increase in sugar levels
• Decreased risk of downy mildew and grey rot
• Decreased vigour due to increased resistance to sap flow
• Increased drought sensitivity

Canopy shape

Features of an ideal canopy (for cool climates):

• Maximum exposed leaf area
• Homogeneous canopy density at 15 shoots/metre
• Homogeneous canopy thickness of 1 leaf or less
• 60% or more fruit exposed
• 10 – 20 node shoot length
• Renewal & fruiting zones well aerated and exposed to the sun
• Shoots droop after veraison
• Trellising is cheap to install and maintain
• Plants establish themselves quickly, and husbandry costs are low
• Machinery designed for its upkeep is available.