This section is from the book "Window Gardening", by S. T. Maynard. Also available from Amazon: Window gardening.
When the soil becomes dry, which may be known by the appearance of the surface of the soil and the sides of the pot, water should be applied until it begins to run into the saucer. No more water should be given until the soil again becomes dry, or nearly so,which will depend upon the dryness of the atmosphere, the amount of soil in the pots, and the foliage upon the plant, when water should be used as before, the true principle being to keep the soil as nearly as possible in the same condition as for the best growth in the out-door garden. More plants are injured by overwatering than by underwatering; yet they should not be allowed to get so dry as to wilt. When plants are growing rapidly, they should be watered more freely than when at rest.
Helping Mother. From the painting by Jan Verhas.
Pots should be washed as often as mould or fungus growth appears, to allow evaporation and a free access of air.
 
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