Light and Location
Lesson 9 of 14
Without soil to slow it down, a Kratky plant grows as fast as its light allows. Light is often the difference between a full head of lettuce and a pale, stretched one.
How much light
Leafy greens and herbs need bright light for much of the day. A sunny south-facing window can work in the brighter months. In winter, or in a dim room, plants stretch toward the glass and grow thin and pale.
Grow lights
- A simple LED grow light, or a full-spectrum LED shop light, is enough for a few jars of greens.
- Keep the light close to the plants, following the maker's guidance, and raise it as they grow.
- Run it for a long day and use a plug-in timer so the hours stay consistent.
Keep the solution cool
Warm solution holds less oxygen, and roots in warm water are more likely to rot. Oklahoma State University Extension gives 72–75 °F as an optimal solution temperature. A dark jar in hot direct sun can get much warmer than that, so if you grow on a sunny sill, shade the container itself while the leaves get the light.
Signs the light is wrong
- Too little: long, floppy stems; pale leaves; plants leaning hard toward the window.
- Too hot: wilting in the afternoon even though roots reach the solution; warm jars.
Your task for this lesson
Choose the spot for your container and look at it at different times of day. If the light is weak or only lasts a few hours, plan for a grow light.
Sources
- Dunn, B. and Singh, H. Oklahoma State University Extension. Electrical Conductivity and pH Guide for Hydroponics (HLA-6722).