Sunshine has several effects on vine growth:

• Indirect effect due to heat accumulation
• Direct effect (through phytochromes) on:
  • Bud viability
  • Floral initiation
  • Ripening
  • Cane maturation

Vitis vinifera is thought to require at least 1250 hours of sunshine to produce ripe fruit. Sunshine hours decrease as you get further away from the coast, particularly the south coast, and with increased height above sea level. The amount of sunshine will also be decreased if the vineyard is close to a large town or city (by up to 10 %!), or if it is shaded by buildings, trees, hills, etc.
Sunshine hours can be measured using a Campbell-Stokes recorder.

It is important to note that high sunshine and temperatures can lead to berry scorching (even in England!), particularly after leaf stripping or spray application.