Plants can tolerate deficiencies in light and feeding for a while, but if you deprive them of water they will die. How long this takes depends both on the plant and on the growing conditions. For example, a succulent that stores moisture within its tissue will last much longer than a young seedling, which has no reserves on which to draw. And a plant that is kept in a humid environment, such as a steamy bathroom, will survive much longer between waterings than one that is kept in an arid, centrally heated living room.
The water taken up by the plant is used to transport chemicals around within the cells, moving nutrients up from the roots, and sugars and starches down from the leaves. It keeps the plant turgid (firm to the touch and able to support its own weight), the cells full and rigid, and allows the chemical reactions that keep the plant alive, such as photosynthesis. Without adequate water, chemical reactions stop and the cells start to deflate, resulting in a flaccid (pale and floppy) plant. Nutrients and sugars no longer pass through the plant, causing the structure to collapse as moisture is lost through transpiration and not replaced.
Each plant can tolerate wilting to a certain point and still make a full recovery, although some permanent cell-death may show as brown ends to the leaves. This permanent wilting point varies from plant to plant, as does the amount of water needed on a daily basis. The only sure way to maintain adequate levels of water is to get to know your plant’s individual needs.
Such plants as rosette-forming bromeliads need watering into their central cup, rather than the pot, because they absorb moisture through their leaves as well as their roots. Plants with hairy leaves should be watered from below, because water spilled On the surface of the leaves can become trapped by the hairs, resulting in scorch marks where it is magnified by the light. Acid-loving plants, such as azaleas, benefit from being watered with rainwater (which is generally soft), especially in areas where tap water is “hard.” For most plants, a little water done frequently is far better than periodic di -owning followed by drought.
During a short vacation, plants can survive without special treatment, as long as they are thoroughly watered beforehand and moved to a cool position. For a longer period, however, it will be necessary to make contingency plans.
There are a number of ways in which plants can still be watered, even during a vacation period, when no one is available to care for them. Wicks and capillary matting both work by allowing plants to absorb as much water as they need from a reservoir. However, these methods will not work if the matting dries out and the capillary column is broken.
Each presoaked wick is placed into a pot by pushing it through the base or by removing the plant from the pot, placing the wick at the side and replacing the plant — the more growing medium the wick is in contact with, the better. Presoaked capillary matting can cope with a greater number of plants. This is placed partially into a plugged sink containing 4—6 in. (10—15 cm) water, and partially on the draining-board. The pots are then placed directly onto the matting, which will remain moist as long as there is water in the sink.
Note that this system relies on contact between the soil mix and the matting, and that it will not work if the pots have a layer of crockery shards in the bottom. A less controlled method of keeping plants moist is by grouping them together on a tray of moist pebbles. The roots stay moist as long as the water level in the tray does not drop too far. However, it is important that the level is not too high initially, or the roots may rot.
Achieving the correct watering levels is often a matter of trial and error, because every plant is different, and each will change throughout its life, and at different times of the year.
There are: various indicators to help the beginner decide when to apply more water (see page 84), but these are no substitutes for practice and observation. By the time the plant wilts, it may be too late to save it, so check it regularly. Lift up the pot (the lighter it is, the drier the potting soil), feel the soil to test dryness. For clay pots, look at the outside — the wetter the soil, the darker the pot.
How much water to apply
Different plants need different levels of watering in order to derive. The terms “thoroughly moist,” “moist,” “slightly dry” or “just moist enough to prevent the soil drying out” are used to indicate how much water each plant needs. To keep the plant thoroughly moist, apply enough water to keep the soil completely moist all the time, though never actually wet.
Do not allow even the surface to dry out. Check every day. To keep it moist, apply water to moisten the soil completely, but allow the top ½ – 1 in. (1—2 cm) to dry out before rewatering. Check every 2—3 days. To keep it slightly dry, moisten the soil completely, but allow the top half of the soil to dry out before rewatering.
Check once a week. The plant might only need to be kept moist enough to prevent the soil drying our during the rest period. Check once a week and give only enough water to keep the potting soil barely moist. Once growth starts again in spring, increase the amount immediately.
Experience is the key to successful watering but in the meantime, recognizing and dealing with problems quickly will help ensure a good recovery.
Underwatering symptoms include: wilted, limp leaves; flowers that fade and fall quickly; a slow rate of growth; falling lower leaves; and leaves showing brown edges If a plant has been underwatered, fill the saucer with water repeatedly, until no more is being absorbed, and then pour away the excess. Never allow your plants to stand in water for long periods of time, since you will deprive the roots of air and, eventually, kill them.
Overwatering symptoms include: soft or rotten patches on leaves; flowers turning moldy; old anc young leaves being shed together; leaves curling, wilting, and turning yellow; leaves with brown tips and the plant having a moldy smell.