Light
The exposure of plants to Light is one of the chief conditions under which they succeed in making their growth. Growth made in the absence of sufficient solar Light consists of weak, elongated shoots that are unable to perform their proper functions. All vegetable life is in an active state throughout the spring and summer, when the amount of heat and Light is correspondingly great; as both diminish in autumn, growth declines, and many plants remain in a somewhat dormant state until the following year. The amount of Light available in winter needs utilising to the fullest extent for plant cultivation, by keeping the glass in all houses and pits frequently cleaned. Heavy blinds permanently fixed on houses, in summer, often prove injurious, by preventing an amount of Light from entering in cloudy weather that would be most beneficial to the occupants. Plants standing in a dark part of a house will be found to grow weak and drawn, compared with others in the same structure similarly situated except in regard to this important element. Light is most essential to all vegetation, on account of the chemical action it causes in the production of colouring matter in the leaves. It is purposely excluded from many vegetables, by closing their outside leaves together or covering the stems with soil, as the case may be, in order to blanch and render the centre or edible portion tender and available for use.