Artifical Light and Plants in the Garden

To the keen gardener with an experimental turn of mind, electric light (provided the correct lamps are used) can be a very useful asset indeed.


This is used to provide high-intensity lighting to plants, seedlings and cuttings to supplement natural light during the winter, and produce vigorous, healthy plants during the early part of the year.

Commercial growers use 400-watt mercury vapour lamps for raising tomato and cucumber seedlings during the early months of the year, but the average gardener will find that fluorescent tubes are quite suitable for this purpose. They can be used singly, or in banks of two, three or four. A 5-ft., 80-watt reflectorized tube will effectively illuminate a bench area of 5 by 1-½ ft. when mounted 2 ft. above the bench. Under such a lamp all manner of seedlings and plants can be grown, and some plants, such as gloxinias and saint-paulias, are quite content to spend the whole of their lives under artificial light.

The lamps can be controlled by a time-switch and burn throughout the day, or they can be switched on at dusk and left burning to extend the day to 16 hours.


With these same lamps it is possible to grow a wide range of plants entirely by artificial light, where a temperature of 60° F. (15° C.) can be maintained. The area the lamp will effectively illuminate and the mounting heights are the same as for supplementary lighting. About 14 to 16 hours would be a suitable period of light each day, but this could be the subject of experimentation.


While there may be some doubts as to the desirability of replacement lighting, there is no doubt that bulb forcing by electric light is useful. In a cellar or shed, one or two ordinary 100-watt electric lamps can be used to force bulbs quickly and easily. Daffodils and tulips are the most suitable. The varieties that are normally forced should be boxed and plunged under peat or ashes in the normal way and brought in for forcing when the shoots are an inch or so high and there is evidence of vigorous root action. Daffodils and tulips should be given 12 hours light out of each 24, with one 100-watt lamp for every sq. yd. of bulbs mounted about 3 ft. above them. If daffodils and tulips are forced together, maintain a temperature of 60 to 65° F. (15 to 18° C). Do not over-water the tulips and never spray the buds or foliage from above.

For hyacinths the treatment is a little different as they require, with the exception of a few varieties, 10 days in the forcing shed in complete darkness at 75° F. (24° C). From then on, 12 hours artificial light can be given each day and the temperature lowered to 70° F. (21° C.)


The time of flowering of mid-season and late-flowering chrysanthemums can be delayed by maintaining a day length of over 14-1/2 hours from mid-August until early October.

These varieties are known as short-day plants and do not develop their buds until the length of the day drops below 14-1/2 hours—about mid-August.

Quite low intensity light is sufficient for this purpose and is applied by hanging 100-watt tungsten lamps over the plants out on the standing ground. The lamps are mounted at 6-ft. intervals 6 ft. above the rows, each line of lamps being sufficient for a 4-ft. bed.

The best response is obtained by switching the lamps on each night from midnight until 2 am by a time-switch.


In addition to these various applications there are several other uses of electricity, such as automatic watering and mist propagation, a method by which cuttings are automatically sprayed with a fine mist.

The combination of a number of these applications in a greenhouse or frame can make it completely automatic.

16. February 2012 by Dave Pinkney
Categories: Featured Articles, Garden Management, Gardening Calendar | Tags: , , , | Comments Off on Artifical Light and Plants in the Garden


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