Run a grow light for 12 to 16 hours a day. Start at 14 and adjust according to how the plant responds.
Why So Much Longer Than Sunlight
Strawberries outdoors do well on 6 to 8 hours of direct sun. Even a good LED grow light is far weaker than the midday sun, so the plant needs more hours under it to collect the same total light over a day. Hours and brightness trade off against each other: a stronger light needs fewer hours, a weaker one needs more.
Do Not Run It All Night
Plants use the dark hours too. Leaving a light on around the clock gains little, wastes power and can stress the plant. Give strawberries at least 8 hours of darkness.
Use a Timer
A cheap plug-in timer keeps the schedule steady, which matters more than the exact number of hours. Set it once and leave it.
Adjusting by What You See
- Long, thin stalks and pale leaves: not enough light. Add hours or lower the lamp.
- Bleached patches or leaf edges curling up: too intense. Raise the lamp.
- Healthy leaves but no flowers: check temperature as well as light. Many varieties stop flowering when it is too warm.
Variety Matters
Day-neutral varieties flower at any day length, so they suit a fixed schedule under lights. June-bearing varieties need short days to form flower buds, and long hours under a lamp can stop them fruiting altogether.
Related guide: Light requirements for Kratky strawberries.
