Bringing light to where plants need it most

Indoors, light is almost always what limits growth. Far from a window, or in winter when days get shorter, herbs stretch, turn pale and produce little. A well-set grow light changes that, and a multi-level shelf multiplies the growing surface without taking up more floor space.

For a home shelf, a white LED strip of 20 to 40 real watts is enough to light seedlings, microgreens or herbs. Go by the power actually drawn, not an 'equivalent' wattage, hang the lamp 20 to 30 cm above the seedlings, and set 14 to 16 hours for herbs. A light, humidity and temperature sensor helps you fine-tune these settings without guessing.

All the benchmarks are gathered in the guide grow lights indoors. To sow under a lamp at the right time, follow the indoor sowing calendar.

Light comes first

A few metres from a window, light intensity drops sharply, even if the room looks bright to the eye. The signs of a lack of light are easy to spot: elongated stems, pale, widely spaced leaves, plants leaning towards the window.

Choosing grow lighting

• Spectrum: a white LED, full-spectrum or warm, suits herbs and leafy greens and stays pleasant in a living space, unlike pink-violet lights.
• Distance: follow the manufacturer's recommendations and raise the lamp as the plants grow.
• Duration: most herbs enjoy 12 to 16 hours of light a day. A timer guarantees consistency and preserves a period of darkness.

Growing vertically

Multi-level shelves and grow towers multiply the available surface without taking up more floor space. Check that each level has its own lighting and that the height between shelves suits the plants you're aiming for: shallow for microgreens, more generous for salad leaves or basil. Glass wall planters suit undemanding plants placed near a window.

Measuring for better watering

A humidity, light and temperature sensor helps you understand what's happening at the base of the plants. In particular, it prevents overwatering, a common mistake indoors.

Going further

The guide hydroponics or soil compares the two methods, and Indoor hydroponics, no jargon explains how to grow with no soil.