Garden innovations - daylight bulbs

Plants require adequate light to perform photosynthesis, the process by which they make food from carbon dioxide and water. Sunlight, although it appears white to our eyes actually blends a broad spectrum of light waves from ultra-violet to infra-red, which we can't distinguish because our eyes are adapted for light only in certain areas of the spectrum. Basically speaking, most plants need blue green spectrum light for vegetative growth and red orange spectrum light for budding and flowering. Many florists and garden centres now have special bulbs that shine all night to ensure their plants don't close up, so the first customers of the day are presented with shrubs and pot-plants in full bloom.

While plants thrive outdoors in even weak sunshine, because it contains this wide spectrum of colour, standard household lighting tends to focus on the yellow light waves in the middle of the spectrum. This is because we like this colour, rather than for any other reason. There are several methods for balancing light to meet plant needs but the easiest is to invest in some special plant growing bulbs, normally called wide-spectrum or full-spectrum lights because of the range of waves they provide.

A cheaper, but less reliable way, is to try to create a balanced light spectrum with one cool white and one warm white fluorescent bulb. These bulbs are good because they provide light without heat, which means you can get the plants close to the lights without risking scorching the way you would with household bulbs.

However, if you're feeling mean, or adventurous, or both, you can try using normal household bulbs to increase the light spectrum. Many hobby gardeners have good success, especially in the winter months, by using one 'warm' bulb (often sold as 'kitchen and bath' or 'soft' lights in DIY stores) which tend to have more of the red and/or blue wavelengths and one 'cool' or standard bulb in a two bulb light fitting to provide a 'fuller spectrum' of light. You will need to rotate plants at least once a day under the bulbs for this to work.

Garden innovation daylight bulb photograph by katmere, used under a creative commons attribution licence.