Growing LIGHTING 101

In this extract from Leslie F Halleck’s book, Plant Parenting, find out how you can use artificial lights to get a head start with seedlings and cuttings

If you’re growing in a space with little to no natural light, then artificial grow lighting is mandatory for plant propagation and growth. Seedlings, in particular, will almost always require grow lights.

The time of year you propagate indoors will also influence your lighting needs. If you start your seeds or take cuttings indoors during the winter months, you will find the lack of light and briefer duration of light can really slow things down. Short winter day lengths, a lower angle of the sun and cloudy days all reduce the amount of natural light available to plants in your home.

Seedlings require intense amounts of light for specific durations and most windowsills simply are not bright enough, for a long enough duration, for healthy seedlings. Conversely, vegetative cuttings you are rooting in soil, water, or other growing media don’t require a lot of bright light – they only need the amount of light that they would receive in a bright windowsill. Cuttings can benefit from 24 hours of lower intensity light until they root.

So, the rule of thumb is that you will need grow lights for seedlings and bright ambient light for cuttings.

DURATION AND DISTANCE OF LIGHT

Once a seedling shoot emerges from beneath the soil, both the amount of bright light and the duration of light are important. After sprouting, seedlings will need 14 to 16 hours of bright light to grow strong and sturdy. This is not because all seedlings are ‘long-day plants’ (which is a reference to a photoperiodic requirement) as you might find them erroneously described in any number of online resources. It is simply because they need a lot of light and it takes that many hours of bright light to deliver what seedlings need.