On a shelf or in a grow cabinet
Growing on a shelf or in a grow cabinet
A shelf in a cupboard, a bookshelf, or a metre-wide grow cabinet: the moment you control the light yourself, you stop depending on which way your window faces or what month it is. This is the only space in this guide where January is as productive as June.
At a glance
- Light
- Grow light, 12 to 16 hours a day on a timer
- Pots
- Shallow 15 cm troughs fit best under a lamp
- Season
- All year, independent of outdoors
- Watch out for
- Heat from the lamp and too little air movement
- Level
- Easy, after a one-off setup
Choosing the lamp
An ordinary full-spectrum LED grow light is enough for herbs and leafy crops. The purple lamps you see everywhere work too, but make your plants' colour impossible to judge — under white light you see immediately when something yellows.
Count on twenty to thirty watts per metre of shelf for leaves and herbs. Growing fruiting crops under light pushes that towards a hundred watts and quickly becomes a different project.
Hang the lamp fifteen to thirty centimetres above the plants and raise it as they grow. Too far and seedlings stretch long and floppy; too close scorches the leaves.
How many hours of light
Twelve to fourteen hours a day is standard for herbs and lettuce, sixteen for fast leaf growth. Put the lamp on a timer and leave it: irregular days produce irregular growth.
More is not better. Plants need darkness to respire and move sugars around; eighteen hours or more gives weaker plants and a bigger electricity bill.
Heat, air and water
A lamp warms the shelf. In a closed cabinet the temperature easily passes thirty degrees, where lettuce bolts and herbs wilt. Leave a gap open or add a small fan.
That same fan solves the second problem: still air. Movement makes stems sturdier and keeps mould off damp compost.
More evaporates under a lamp than you would expect. Check every other day with a finger; shallow troughs dry faster than deep pots.
What grows best here
Herbs and leafy crops are the obvious choice: they need little light, stay low, and you harvest continuously rather than once. Mint, basil, loose-leaf lettuce and spinach keep a one-metre shelf productive for months.
Microgreens are the other winner. Ten days from seed to harvest, no depth required, and the yield per centimetre beats any mature plant.
These do well under a lamp
- Growing mint in a potThe plant you have to hold back rather than encourage. Just keep it separate.
- Growing basil on a windowsillThe herb everyone buys and everyone kills. Here is how to keep it alive.
- Growing loose-leaf lettuce in a pot or troughSow once, harvest for six weeks. The best return on a small trough.
Frequently asked questions
How many hours should a grow light be on?
Twelve to fourteen hours a day for herbs and lettuce, up to sixteen for fast leaf growth. Use a timer and keep the rhythm constant. Beyond eighteen hours it backfires: plants need a dark period too.
How far above the plants should the lamp hang?
Fifteen to thirty centimetres, depending on wattage. If seedlings stretch tall and thin, the lamp is too far away; if leaves bleach or scorch, it is too close.
Can I grow tomatoes under a grow light?
You can, but it needs far more light than leaves — towards a hundred watts per square metre — plus height and hand pollination. For a first grow shelf, herbs, lettuce and microgreens are much more rewarding.
Updated on 2026-08-25
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