Watering and Damping Down

A good plantsman, is one who knows how and when to use a watering-can. The watering-can itself is an important piece of equipment and is something well worth paying quite a lot for. Good balance is all-important, and the fine and coarse roses with which the can is fitted must be efficient, for any dribbling from the end of a rose can do considerable damage to seedlings.

Roses are only needed when watering seeds, cuttings and very young plants. Also newly potted plants, or the surface compost will be disturbed. Established plants should always be watered direct from the spout of the can, but this should be held close to the soil so that the water does not wash it out of the pot. Sufficient water should be given at each application to soak right through the compost and no more should be given until it begins to dry out.

When to Water

One way of checking the amount of moisture in a clay flower pot is to tap it with something hard such as a cotton reel on the end of a cane. If the pot gives out a clear ring the compost within is dry; if it sounds dull and heavy the compost is wet. With a little practice considerable accuracy can be attained in assessing the plants’ needs.

With plastic pots it is not so easy, as plastic does not give the same results as clay when tapped. One must therefore resort to lifting the pots and judging by their weight if the compost is wet or dry. Alternatively, an assessment can be made of the position by feel or by the colour of the surface compost. This is a more hit and miss method as the surface compost may not truly represent what is underneath.

The moisture needs of plants can vary, tremendously and individual plants will need more or less water according to the season and the stage of their development. With higher temperatures and sun heat the summer is a time when the greenhouse gardener must be particularly alert, for moisture losses on hot, sunny days can be extremely rapid. Spring and autumn are the intermediate seasons in this respect and winter, the time when least watering needs to be done, calls for attention of a different kind. Over-damp conditions then can lead to all kinds of complications with many plants.

It is a sobering thought that more plants are killed by over-watering than under-watering, particularly during the winter months. Certain plants, like fuchsias, poinsettias and gloxinias either need very little or none at all during the winter. On the other hand, if chrysanthemums are allowed to become too dry when the buds are forming this will cause a hard centre to form in the flowers, while if tomatoes on which the fruits are developing become too dry and are then watered. Fruit splitting will result. Vigilance is always necessary and the water requirements of all plants must be checked individually as often as experience proves necessary.

One point which should be specially emphasised is the need to water plants thoroughly a short time before repotting. A dry root ball is extremely difficult to soak after potting has been completed. And inability to correct this condition can have serious consequences.

Automatic Watering

This is the age of automation and one way in which the greenhouse gardener benefits is through automatic watering. This can be a boon to the busy gardener away from home for many hours each day, and for longer periods on occasions. The capillary bench. As it is called, makes use of the ability of plants to take up the moisture they need through capillary action. The pots are stood on a sand-covered bench which is kept permanently wet by means of perforated piping laid in the sand and connected to a header tank. As the plants only take up water to meet their needs they are in fact watered much more precisely than could ever be possible by use of a watering-can and personal judgement. An important point to note, though. Is that plants in clay pots must have wicks through their drainage holes to connect the compost in the pots with the sand base. Plants in plastic pots will take up water without this aid.


Moisture is needed in the air as well as in the soil, but the amount required varies with different plants. Succulents like a much drier atmosphere, for example. Than ferns or foliage plants. Atmospheric moisture can be supplied from evaporating trays, by watering paths and under staging and by syringing between the pots or even over the leaves of plants that like a lot of moisture. This so-called damping down creates in the artificial conditions of the greenhouse the growing atmosphere which is so essential. In summer it is often done in the early morning, at midday and towards evening, when closing down the greenhouse. In late spring and early summer I like to damp down and close the ventilators at the end of the afternoon and the combination of a rising temperature and atmospheric moisture creates just the kind of growing conditions I have referred to. This is especially necessary after pollinating peach trees and spraying tomatoes to help set the fruit. Damping down also keeps red spider at bay, another important factor.

01. March 2012 by admin
Categories: Featured, Greenhouse Gardening | Tags: , , , , , | Comments Off on Watering and Damping Down


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