A cuke grown in full sun receives six or more hours of daily sun (more is better.) In other words, it has direct sunlight for a minimum of six hours nearly every day from planting to harvest. You can’t stop cloudy or rainy days, of course. But if it’s possible, plant cukes where trees and structures don’t block the sun.
Expert gardener’s tip: Where summer afternoon temperatures regularly exceed 85°F (29.4°C), planting cukes with full morning sun and no more than 3 hours of afternoon shade is acceptable.
Problems with Excessive Sun
Sun exposure maybe a problem for indoor-started cukes started when transplanted to the garden. They respond by dropping the “shade leaves” they developed to photosynthesize indoor light. To help them adjust, harden the cukes off before planting by exposing them to increasing amounts of sunlight each day.
How to Handle Dropping Leaves
If you’ve already planted indoor-stated cukes and they’ve dropped their leaves, don’t panic. They’ll grow replacements if you:
Water just enough to keep their soil moist to the touch. As the new leaves come in, gradually increase watering.
Fertilize the cukes at a reduced rate to keep the plants keep growing. Wait until the new leaves have come in to resume your regular fertilizer program.
Problems with Excessive Shade
As rapidly growing and fruiting vines, cucumbers struggle to get all the sun they can — even if it means growing taller or longer than normal to clear a shade-throwing obstacle. That extra growth comes at the expense of fruit production.
Cucumbers growing in too much shade are susceptible to powdery mildew infection. Affected leaves develop a powdery white coating before turning brown and falling. A serious case can wipe out your cuke harvest.
Maximizing Sun Exposure
If giving your cukes six hours of daily sun seems questionable, these measures may provide the answer :
Plant on a North-South Axis
When the long side of your cucumber row runs north and south, full sunlight will hit its entire length as the sun moves across the sky.
Trellis Your Cuke Vines
Cucumbers growing vertically on trellises reach more sunlight than those sprawling on the ground. Trellises also planting shorter bush cucumbers at the bases of the vertical vines. Using a north-south axis gives the trellised and bush cukes equal sun exposure bush throughout the day.
Expert gardener’s tip: If you’re gardening on a slope, make your rows run across it regardless of their axis. They might not maximize the sun exposure, but they’ll keep the soil in place during heavy rain.