Lighting for Kratky Strawberries
Light drives flowering and fruit. Strawberries need a lot of it, and a shortage of light is the most common reason an indoor plant grows leaves but no berries.
Sunlight
Outdoors, or in a very bright window, strawberries want 6 to 8 hours of direct sun a day. A south-facing window is the usual best choice in the northern hemisphere. Behind glass, light falls off quickly with distance, so keep the plant right at the window.
Grow Lights
Indoors away from a window, use a full-spectrum LED grow light.
- Hours: run the light 12 to 16 hours a day. Grow lights are much weaker than the sun, so the plant needs longer under them.
- Timer: put the light on a timer so the schedule stays consistent.
- Distance: follow the maker's guidance for hanging height, then adjust by watching the plant. Raise the light if leaves bleach or curl. Lower it if the plant stretches.
Day Length and Variety
Day-neutral varieties flower regardless of day length, which makes them the easy choice under lights. June-bearing varieties form their flower buds in short, cool days and are much harder to manage indoors.
Temperature
Strawberries grow and set fruit best between about 60 and 80°F (15 to 27°C). Many varieties slow or stop flowering in sustained heat. Lights add warmth, so check the temperature at leaf level, not just in the room.
Signs of Too Little Light
- Long, thin leaf stalks reaching toward the light
- Pale or small leaves
- Few flowers, or none
- Slow growth even though nutrients and pH are right
More Kratky Strawberry Guides
This guide is one of a set covering each part of growing strawberries with the Kratky method, from choosing a container to solving problems.
