Water is the source of life for every plant. Of course, everyone who keeps plants knows this, but the eternal question remains: how often and how much? It would be nice if we could give a general answer to this question, but there simply isn’t one. Here, too, different plants have varying water requirements that are, moreover, dependent on the season and on the location. Plants lose a lot of their moisture through transpiration during the summer, and this need to be taken into account when watering.
It is best to water your plants early in the morning, as this will sustain them against the heat of the day. If the soil of some specimens feels dry again by evening, then go ahead and give them a second watering; spraying the leaves of foliage plants can also have a refreshing affect. It is better for cacti to be dry again before evening, but during particularly warm days they can be included in the early morning watering round, over their crown.
Overwintering plants should be never be watered if the soil still moist and dark in color. And plants that spend the winter in a cool, frost-free room need very little water (one a week will generally suffice), while flowering plants in a heated room should be watered every day. Tropical plants should also be checked daily, but do not water too liberally; if the surface is dry, examine the under surface by pushing your finger into the soil. Cacti, with the exception of the leaf cacti, can do without water entirely between November and March (at a temperature of 10 degree Celsius maximum), and plant that drop all their foliage in the autumn can also remain dry during the winter. These include Achimenes, Sinningia, Rechsteineria and Hippeastrum (10-12 degree Celsius).
Most Plants dislike wet feet, so any water that drains through the soil into the saucer (or into the ornamental outer container) after watering should be removed after 30 minutes. This water cools down too sharply, and cold water is never good for the roots of the houseplant, not even in the summer.
It is therefore important always to have water at room temperature to hand. Make a habit of refilling the watering can as soon as it is empty and leave it standing in the same, fairly warm place,then you can be sure that the water will always be at the right temperature. As far as your watering can is concerned, apart from aesthetic considerations as to its shape and color, choose one with a good long spout that can reach under the foliage direct to the soil without spilling.
Authors: A. C. Muller-Idzerda, Elisabeth de Lestrieux, Jonneke Krans