Greenhouse light

From Gardening Wiki

Greenhouse Light

In order to appreciate the importance of maximum light in a greenhouse we must realize that about 95 per cent of the substances contained in the plant is derived from the atmosphere. Through the action of light on the green matter located principally in the leaves, these substances, combined with water, are manufactured into plant food. This process takes place in the daytime under the influence of light. The foods thus manufactured are used during the night, for contrary to general belief, plants make most growth at night.

Thus it can be seen that maximum light conditions tend toward large food manufacture and a consequent healthy growth. The light assists in the development of supportive tissues which enable the plant to resist attacks of various diseases.

Lack of proper light in greenhouses causes the plants to possess little or no resistance to disease, and this is especially true during the winter months. Roses, tomatoes and cucumbers,for example, require more light during this time than many ordinary houses are able to furnish.

An excess of light such as is experienced during the summer months is also detrimental to plant health in greenhouses and so shading the glass becomes necessary. Furthermore there are numerous conservatory plants such as palms which require less light. Too much light affects the transpiration of these plants and causes them to wilt badly.

Factors which will increase the amount of light in a greenhouse should be encouraged.

Among these are : Large glass with small lap; reduction of size and number of the sash bars, purlins, posts to minimum size; solidly framed houses so breakage of glass will be reduced; the proper roof pitch, practical to build and yet allowing a large percentage of light rays through the glass, as well as clear quickly of condensation, snow and ice; location of the houses so they receive the light from morning until night; and large houses so that the shade-casting members are farther from the glass, thus diffusing the shadows cast on the plants.