How to Choose a Grow Light for Indoor Plants

In a flat, light is usually the thing holding your plants back. A north-facing room, a building across the street or short winter days are enough to turn a fiddle-leaf fig pale or send basil stretching towards the glass. A grow light can make up the difference, as long as you choose the right one. Here's what to look at before you buy.

Signs your plants need more light

Plants turn light into energy through photosynthesis. Through a window pane, and two metres back from it, the amount of light a plant receives drops off sharply, even if the room looks bright to you. The signs of low light are easy to spot:

• long, thin stems leaning towards the window;
• new leaves that are smaller and paler than the old ones;
• variegated leaves turning plain green;
• growth that stalls completely all winter.

If that sounds like your plant, a grow light will make a real difference.

Full spectrum or red and blue?

Plants mainly use blue light, which encourages dense, compact foliage, and red light, which supports growth and flowering. Early grow lights gave off only those two colours, hence their famous purple glow.

Today, full-spectrum LEDs give off a white light that covers all of those wavelengths. For a living room or kitchen, that's the most pleasant choice: plants keep their true colours and the light doesn't look out of place. Red and blue mode is still handy for seedlings, or for plants tucked away in a corner where looks matter less.

Wattage and distance

For a few houseplants or a small kitchen herb garden, there's no need for a very powerful light: an LED of 15 to 30 W is plenty. What matters most is the distance between the light and the leaves:

• 20 to 40 cm for most foliage plants and herbs;
• 10 to 20 cm for seedlings, which need intense light to stay short and sturdy;
• a little higher for shade lovers such as pothos or ferns.

If the top leaves turn yellow or show bleached patches, move the light further away. If the stems keep stretching, bring it closer.

How many hours of light?

Plants need a period of light, but they also need a period of darkness. As a general rule:

• 8 to 10 hours for foliage plants that already get some natural light;
• 12 to 14 hours for herbs and other light-hungry plants;
• 14 to 16 hours for seedlings.

The timer is the most underrated feature of all. Switching a light on and off by hand is something you'll forget sooner or later, yet a steady routine is exactly what helps a plant thrive. That's why our full-spectrum clip-on LED grow light offers 4, 8 or 12-hour cycles that restart automatically every day.

Clip-on, hanging or all-in-one?

The right format depends on your setup:

• A clip-on light clips onto a shelf or desk. Its flexible arms point at one or two plants, making it the most versatile option.
• A hanging light or LED bar works better for a whole shelf of plants.
• An indoor herb garden with a built-in light is ideal if your goal is growing herbs: light, water and timer are all taken care of. Our LED hydroponic herb garden, for example, lights its six pods for 16 hours a day without you lifting a finger.

What about electricity?

LEDs are very efficient. A 20 W light running 12 hours a day uses about 0.24 kWh, or just over 7 kWh a month. That's very little compared with most household appliances, and nothing like the old bulb-based grow lamps.

Common mistakes to avoid

• Placing the light too far away: a metre above the leaves, its effect is very weak.
• Leaving it on day and night: most plants need darkness to grow properly.
• Forgetting to adjust watering: a plant getting more light grows more and drinks more.
• Changing the settings every day: give your plant one or two weeks to adapt before judging the results.

The bottom line

To choose the right grow light, go for an adjustable full-spectrum LED of 15 to 30 W with a built-in timer, and position it 20 to 40 cm above your plants. With those settings, even a dark flat can be home to a lush green corner all year round.