How often should I water? This question would with out doubt be the most asked question by the new or novice grower. The easy answer is of course water your plants only when they need it, but how does one go about determining when they need it?
Plants need water for the process of photosynthesis. They need water when they are in active growth and they need water when they are transpiring heavily. From this it could possibly be said that for plants under shade-house conditions it is almost impossible to over-water in summer and conversely it is almost impossible to under water in winter. This is assuming of course that the plants have adequate drainage. Generally during the very hot summer months when the air is extremely dry most growers find it necessary to water twice a day. In winter once a week or even once a fortnight may be sufficient. It is something of a paradox that the further we are away from the equator the more watering is required. This is due to the fact that the humidity is much lower in the temperate regions and must be compensated for by using more moisture retaining material and more frequent watering.
This then leaves autumn and spring as the seasons that give most trouble. In spring a good indicator of watering needs is the condition of the root tips. If you can see green tips on the ends of the roots then the plant is commencing active growth, so it is time to begin regular watering. If the roots are not active the plant will not be able to, no will it require much water. In such cases water can not only rot roots and set the plant back but the excess water may encourage fungal disease.
In autumn as the days shorten and the nights grow longer most plants move slowly into dormancy. Decreasing the frequency depends not only on the season but also the potting medium or type of mount, the size of the container and the plants? position in the shade-house relative to sunlight and air movement. A fine potting medium will retain more moisture than a course mix, a cork mount will dry quicker than a treefern mount, a plant suspended near the roof will need more water than those in a cooler position.
Experienced growers are usually able to tell by their nose when a shade-house has sufficient humidity. A humid shade-house has a particular smell about it, what the old books referred to a "a buoyant atmosphere". There is no substitute for experience in this. Until your nose develops this sense of smell you should be particularly attentive when visiting the shade-houses of other growers and take note of the smell and feel of the atmosphere within the house.
Some further points to bear in mind are that no two shade-houses are identical and what works for one grower will not necessarily work for another. Different combinations of temperature, light and humidity produce a wide range of differing requirements. Don't follow other people's advice slavishly and don't be afraid to experiment.