Neon light has lots of blue colours.

Photo: Grøn Kommunikation
Written by Lars Lund 
Edited by Louise Curley

Plants need light in order to grow, but there aren’t always sufficient amounts of sunlight available, for example during the short days of winter or when growing indoors. This can be a problem, particularly in late winter and early spring when gardeners need to sow indoors the seeds of some plants, such as tomatoes, chillies and aubergines. Even though in February the days are getting longer, there are still only 9–10 hours of daylight compared to 18 hours in midsummer, and the intensity of the light is much weaker as the sun is still low in the sky and cloudy days are more common.  

A lack of enough light results in spindly seedlings that grow tall and leggy as they stretch towards the light. These plants will grow with weakened stems, and they’re less likely to be able to fend off pests and diseases, especially the fungal disease known as damping off.

The spectrum of light is made up of the colours of the rainbow, but plants absorb mainly blue and red light. Blue and red light stimulates growth, with red light also used for flower production. Normal household light bulbs don’t provide the type of light plants need, but it is possible to buy special horticultural lighting which can be used to give plants grown indoors a boost.

LED grow lights contain the right spectrum of light for plant growth, and they’re energy efficient, which is good news as you’ll need to leave them on for between 12–16 hours each day. They’re also completely recyclable and don’t contain toxic chemicals like other types of bulbs.

There’s a whole range of products depending on your available space and how many plants you’ll need to light, including planters and propagation units that come with integrated lighting to ones that look like a desk lamp. Companies that specialise in equipment for hydroponic growing are a good place to look for more advice, but as indoor growing becomes increasingly popular brands such as Elho and Parus are designing grow light products suitable for small scale growing at home.