The obvious effect of an underwatered plant is that it wilts and becomes limp and unsightly. However, there are other clues to look for.
Flowering plants are more quickly affected by dry compost than those grown just for their foliage. Therefore, always ensure that flowering plants are adequately watered, even when they bloom in winter. Watch out for flowers that wilt and fall off.
- Another sign of dry compost is wilting, yellow leaves. Dry, brittle leaves also mean the plant lacks moisture.
- When a plant wilts, droops, and looks unsightly it is a signal that the compost may be too dry. Take fast action to save it.
- Large plants, especially those growing in a relatively small pot —will quickly suffer from lack of water.
- Plants which need to be repotted will also quickly suffer from lack of water.
Reviving Underwatered Plants
If the plant is small enough to pick up, submerge the pot and root-ball in a bucket of water until bubbles stop rising. Put it where excess water can run away before replacing the plant in its usual place.
Large, floor-standing plants will have to be watered from the top. However, when the compost dries out it contracts and leaves a gap through which the water will pour out of the bottom of the pot. First, break up the surface compost without damaging the roots. Several waterings will be necessary, as the first will just cause the compost to expand.
If your plant has suffered badly from lack of water, remove any affected flowers and stand in slight shade until it recovers.
Giving plants the exact amount of water they require is one of the most difficult aspects of keeping house plants alive indoors, where they are living in artificial conditions.
If the compost is too wet, the roots stop functioning and the plant will wilt and eventually die. If the compost is allowed to become dry the plant will also wilt. Watering a dry plant will probably lead to its recovery, although when water is withheld over a long period there is a point at which however much water you give it, the plant will not recover.
A plant growing in a garden has plenty of soil around it to absorb water, which can also usually drain through to the lower depths of the soil. A house plant, however, has a relatively small amount of compost, which can easily fluctuate from being just moist to either being waterlogged or being absolutely bone dry.
Different watering needs of plants
Plants differ in their need for water. The Umbrella Plant (Cyperus altemifolius), for example, and its close relative Cyperus diffusus, do not mind having their roots continually in water and are best grown with their pots in a saucer kept full of water. However, other plants such as succulents need water only when the compost shows signs of drying out. Many plants, except those in flower, need less water in winter.
Overwatering
There are a number of symptoms of over-watering.
- The plant will start to wilt because the roots have become inactive and cannot absorb moisture. Even though there is plenty of moisture in the compost, the fine roots’ hairs have rotted away and the plant cannot use the water. The compost and pot may become covered with slime.
- The upper leaves may curl and turn yellow, and eventually fall. Flowers may become limp and mouldy, and soft stems may rot.
Reviving an overwatered plant
The first thing you must do of course is to stop watering the plant. If it is small, remove the pot so that the roots and soil-ball are exposed to the air and leave the soil-ball to dry out —but not so that the corn-post starts to crumble. Use newspaper or blotting paper to absorb excess water. Then replace the plant into its pot, after checking that the drainage hole is free and the pot is clean.
- Until the plant is growing strongly again, put it in a partially-shaded spot.
- The African Violet on the far left is healthy, but the roots of the other one have completely rotted away due to overwatering.
Watering Tips
Judging if compost is dry
- Dry compost weighs less; with small plants in small pots you can judge if the compost needs water by lifting up the pot.
- However, to do this you need to have quite a bit of experience with house plants and it is impractical with large plants.
- A finger can be pressed into the compost to judge if it is moist. However, continually pressing down the compost may cause it to compact, excluding air and encouraging waterlogging.
Clay pots
- Tapping a clay pot is a well-tried method of assessing if water is needed, but it is useless reservoir of water that can be drawn on to keep the potting compost moist over several weeks.
- The compost draws water from the reservoir constantly by capillary action, so that the plant does not dry out due to lack of available water.
- The philosophy behind this is that as the compost dries it shrinks, leaving a gap between the soil-ball and the pot. If a dry clay pot is tapped it rings.
