Plants process light just as we use food. Whether from the sun or from artificial sources, green pigmentation (chlorophyll in African violet leaves) absorbs solar energy which allows the plant to either use it for growth or store it for future use. This is why fertilizers are not the true plant food; the only true food plants get is from sunlight.

The Facts of Light

The word “photosynthesis” means the manufacture of carbohydrates (sugar and starch) necessary for growth in plants. The light is used for energy; carbon dioxide and water derived from the air and the soil are the major building blocks. This process occurs only in the green parts of the plant, in specialized organs known as chloroplasts which are rich in chlorophyll making them green in colour.

Growing in Windows versus Growing in Light Gardens

Mona's Plant Window

Why even consider artificial light for growing African violets or any other houseplant for that matter?  Yes, the sun emits light at a relatively steady rate, but our plants don’t always get the benefits of this consistency. Most of us do not live in the tropics where light intensity and day length are different from our own. We experience sharp drops especially during the winter to the point where many plants simply do not get enough light for good growth. In summer our sun can get to extremes where there is more light than the plant can handle. Even cloud cover for days on end can prevent our well placed plants from getting the light they need. Insufficient window light pushes plant hobbyists to look for good quality, inexpensive substitutes for sunlight.

Plants grown in light gardens have the advantage of constant, equal light intensities and durations through the year and throughout the cycles of the plant. It is not necessary for them to deal with rapidly changing temperatures when the summer sun shines down on them or when our cold winter  air gets to them through a simple pane of glass. Even dry air is rarely a major problem since large numbers of plants are naturally grouped together in a light garden creating a humid microclimate which African violets adore. Light gardening also allows hobbyists to place plants where they want them to be rather than having to make sure there is a suitably oriented window nearby.

All this is not to say it is not possible to grow beautiful, symmetrical African violets with window light.  It has been done and is presently being done by many growers.

Choosing the Right Light

Artificial light is beneficial but what kind is best for our African violets? Let us study the three major kinds available to home growers: incandescent, High Intensity Discharge (HID) and fluorescent.

1. Incandescent Light

 Incandescent bulbs are the common light bulbs we use in our homes. These give off about 70% of their energy as heat. Plants grown under these can be easily scorched and also will dry out rapidly. The heat problem means that plants which need a fair amount of light for good growth and bloom, such as African violets, have to be placed so far from the bulb to avoid the negative effects of heat that they are no longer getting enough light intensity for healthy growth and flowering. Either too hot or not enough intensity: it’s a truly vicious circle!

Incandescent bulbs also tend to produce mostly red and far red light rays, a very poor balance which gives weak, floppy growth although it does stimulate flowering. In general, incandescent light is a poor choice for plants depending entirely on artificial light.

Incandescent bulbs can however be very helpful for plants which get some natural light but not enough for good flowering, such as those grown in a north window. These are typically plants which look fairly healthy but which bloom sparsely or not at all. Even an incandescent bulb placed quite a distance away from the plants will supply some extra light that is often enough to encourage the plant to bloom. Such supplemental lighting is often most useful during the winter months.

 2. High Intensity Discharge (HID)

HID lights, including halogen lamps, sodium lamps, mercury vapour lamps, etc. are currently very popular in large commercial installations such as greenhouses, office buildings, atriums and shopping centres where they are appreciated for the great intensity of light given off. In fact a single HID lamp can brilliantly light every nook and cranny of a fair-sized room. However, the current forms of HID plant lamps are extremely intense, much too hot and too glaring for home use. Undoubtedly useful HID lamps of weaker intensity will be used more and more in home growing in future years.