Dehydration in Houseplants

Scorching on the leaves is caused by dehydration, due to underwatering or too much heat. Dehydration (lack of water) affects plants in different ways, but its effect is always traumatic.

Lack of sufficient water over a prolonged period can be fatal to plants. Keep an alert eye open for tell-tale danger signals and take prompt action to avoid disaster.

There are several degrees of dehydration, ranging from mild drooping to severe drying out. In some plants (begonias, Busy Lizzie, and Spider Plant) the first signs of drought can be a lightening of the whole appearance of the plant. The leaves, particularly, can pale in colour by several shades. Begonia and Busy Lizzie leaves are not permanently damaged at this stage, but unless they get watered immediately, they very soon will be.

With most plants, the first sign of dehydration is that the stems and leaves start to droop. Next, the leaves will hang loosely as if lacking in substance, as indeed they are, for it is water that keeps them turgid. Lastly, the stems keel over, the flowers wither and the flower buds fall off.

Some plants may appear to be completely unaffected by some small degree of dehydration. They apparently recover swiftly and completely when the potting mixture is throughly moistened. But this is deceptive, as the plant has usually been seriously debilitated.

Most plants that dry out at the roots, to the point where they droop, will have had damage done to the cellular structure of the leaves and stems. This shows as shrivelled leaf edges and leaf tips, brown or otherwise discoloured patches or shrivelled sections. The marks cannot be eliminated and will stay with the plant until the particular leaves or stems are shed. Severe cases will result in the total loss of whole sections of the plant or the complete plant. Ferns are especially vulnerable to dry conditions.

How to Avoid Dehydration

• Never allow a plant to get so dry at the roots that its leaves droop appreciably.
• Plants that have filled their pots with roots will dry out very quickly. When they are grown in a peat-based compost the mixture can also dry out quickly. It then shrinks, and a gap appears between the rootball and the inside walls of the pot. Any water applied tends to run straight through the gap.
• Overcome this problem by soaking the pot and rootball in a deep bowl or bucket of water for 15-20 minutes, until the compost has soaked up the required amount of water.
• A high level of humidity around the plant will mean that less water is lost by the plant through its transpiration. Stand the plants on generous-sized dishes or trays filled with pebbles which are kept moist. Mist spraying also helps a little.
• Avoid standing thin-leaved plants in hot, dry positions such as near radiators. Protect or shield the pots of plants grown in warm sunny windows from the direct rays of the sun. You can use a second, outer container and fill the gap between the two with moist peat.
• Cover the surface of the potting mixture with a layer of grit to reduce evaporation from the top of the compost.

How to Counteract the Effects of Dehydration

• If a plant droops or collapses, first water it, generously mist spray it and move it out of sunlight or away from artificial heat. This may solve the problem.
• If the rootball has contracted, soak the pot and rootball in a deep bowl or bucket filled with water for 1520 minutes.
• Damaged leaves or stems will not lose their marks. Cut brown or blackened leaf tips away with scissors and trim away any shrivelled or discoloured pieces to improve the appearance of the plant after you have revived it.