Correct Amount of Water And Humidity For Plants

Water plants – don’t drown them!

Water is essential to plants, they cannot live without it. With few exceptions they cannot live in it either! More plants die from drowning than any other cause. This most commonly occurs when people stick to rigid rules about watering and at, say 9.0 am give each plant its daily half pint, whether it wants it or not.

water-lilly[4]Plants with thick, fleshy leaves hold more water and need less frequent watering than thinner leaved varieties. Thinner leaves have much greater surface areas, their evaporation loss is higher, and the plants need more regular attention. Another important factor is the season. In winter, growth slows and may even stop. The plant is less active and the demand for water is reduced. The situation is reversed when growth begins again. As growth becomes more vigorous, more water is required. As temperature and light are increased, so growth is stimulated, and the plants again need more water.

It should be clear that the nearest a plant can get to being a regular ‘Daily Pinta’ drinker is to be a water lily. Having decided the factors which govern the demand for water, it is now necessary to say something about the type of water. There are, in fact, a number of kinds, but we are concerned with two – tap water and soft rainwater.

Rainwater (chemically neutral) is virtually pure. Even when collected in a butt from the roof it will contain only odd impurities that are unlikely to adversely affect the plant. It is usually warmer than tap water. Its lime content is either zero or insignificant. You can easily ‘go wrong’ with tap water, never with rainwater.

Tap water (normally alkaline) always contains chemicals ; chlorine, for example, is used to purify it. Considerable quantities of calcium (lime) are frequently present because tap water is collected in reservoirs from watersheds, which in many places are of limestone. Nowadays, fluoride is often added, too.

Lime is not a plant food; its function is to interact with other material in the soil. By doing so it sets free nutrients which would not otherwise be soluble, and makes them available to the plant roots. This suits a large group of plants which accept the alkalinity of the soil created by the lime. Such plants are known as ‘lime tolerant’.

However, almost all indoor plants prefer an acid soil which must therefore be lime-free. The constant use of tap water containing lime results in a build-up of lime in the soil and makes it inhospitable to indoor plants. Such plants will respond by turning yellow, looking sick and finally dying.

When rainwater is not available, the answer is to boil tap water and then leave it to cool before using it on your indoor plants. Most of the lime content will be deposited in the kettle in the form of fur.

For those interested in technical terms, the alkaline-acid conditions of compost, etc., are regularly referred to as the pH Factor, and the following is given as a guide.

  • PH 6.5 Slightly acid
  • pH 7 Neutral
  • pH 7.5 Slightly alkaline

Watering is the key

No area of indoor plant care demands the ability to ‘plant-think’ more than the question of when to water. Never go by the clock, but think in terms of maintaining the right soil condition. Each day, take whatever action is necessary to provide the right amount of water for each individual plant. The right soil condition for each plant is described under their individual entry.

  • To give water when the plants need it means that you must regularly test the soil first by pressing your thumb on its surface.
  • Wet Soil feels soggy and lifeless; the thumb makes a mark which tends to linger and particles of soil will adhere to the thumb.
  • Moist Soil will feel springy and the thumb mark will probably disappear as it would if you pressed a sponge. Particles of soil will adhere to the thumb.
  • Dry Soil feels dry and firm, often hard. It will not give to thumb pressure and few, if any, particles will adhere to your thumb.

correct wateringThe Watering Technique

First check the soil and decide whether to water!

For watering, use a can of comfortable size with a long, narrow spout which will slip easily under the leaves of the plant and reach the soil at the base of the stems. Fill the space between the soil and the rim of the pot. The water will drain through the soil into the saucer in which the pot is standing.

Empty it; do not leave this residue in the saucer.

Only two popular indoor plants like the water to be left in the saucer, they are Cyperus (Umbrella Plant) and Helxine (Mind Your Own Business).

Some plants dislike water in their crowns or on their corms – Gloxinia and Cyclamen are typical examples. It is better to water them from below. To do this, immerse the pots in water to soil level; leave them to soak until the top of the soil feels moist to thumb pressure. This can usually be seen as well – the soil glistens slightly. When they reach this stage, stand the pots somewhere to drain out, and then return them to their growing positions.

If top watering is unavoidable, do so with great care and do not wet the crowns of the plants.

Watering Difficultieswatering problems

(1) Water runs straight through because soil has dried out and shrunk : remedy this by immersing the pot in bucket or trough with water to soil level. Leave to soak until soil surface glistens. Gently loosen surface soil with an old table fork.

(2) Water not soaking into the soil but remaining on top in a pool: the remedy for this is to prick the surface of the soil with a fork so that it is friable and broken up and then immerse the pot in water as directed in (1) above.

Good Watering

  • The water permeates the soil, any excess draining into the plant saucer to be emptied away.
  • If you are in any doubt as to whether your plant needs water or not – wait another day. Remember, more plants die from over-watering than any other reason.
  • In winter, in unheated or cool rooms, water in the morning. Don’t use cold water, make sure it is tepid or lukewarm.
  • In summer, never water if the plant is in full sunlight. If you do, and the leaves are splashed, the droplets can act like tiny lenses and burn the leaves.

Correct Humidity Levels For House Plants

To most house plants, moist air is more vital than warm air; they have a desperate need for humidity. Many of them had their origins in the rain forests or other lush growing areas of the world, where good supplies of light, warmth and food led to vigorous growth. This, in turn, resulted in larger leaves or many smaller ones increasing the total leaf areas in order to keep pace with the requirements of food to sustain growth.

creating humidity for plants

These environments were made lush by plentiful rainfall. The vigorous growth would soon have run into an evaporation problem but for the high rainfall. Although high temperatures cause evaporation of moisture from the soil, moist warm air is retained near the ground by the tree canopy overhead – hence `steaming jungle’.

Our indoor plants are often scaled-down models of these jungle plants, and their humidity needs are scaled down too, as is their light-warmth-water balance. But they have evolved with humidity as a vital factor of the life balance and must have it in similar proportions to the other factors in the balance.

There are some indoor plants which do not need humidity. Cacti are the obvious example, originating as they do from the arid areas of the world. The need for survival has obliged them to find means of countering the hostile conditions forced upon them by climatic changes. They developed thick, water-retaining combined leaves and stems. In many cases they grew round or oval to present the smallest surface area possible. A sphere contains the maximum volume in the minimum surface area and cacti have learned to minimise evaporation by conforming to this shape as closely as they can. They grab all the water they can obtain and give off as little as possible. Creating humidity

Central heating can be a boon to the indoor plant enthusiast since it ensures good control over temperature. Regrettably, central heating also dries the air in the room so that some means of providing humidity for the plants must be found. Since it is both impractical and undesirable to increase the humidity of the whole room to the degree required, a Mini-Climate must be created in the air surrounding the plants. This can be achieved fairly easily.

1. Moist Air Bath

Half fill a large plant saucer with pebbles. Push into them a smaller saucer in an inverted position to give the pot steady support. Add water to a level slightly below the base of the plant pot. Replace evaporation loss as necessary.

2. Moist Air Bath For plants in a trough or stand

Fill space between container and the pot with peat. Keep this peat packing thoroughly moist at all times.

3. The Steam Bath

Place a brick, or block of wood, in a large basin and pour in enough boiling water to reach just below the level of the top of the brick.


Indoors this is best done with a hand sprayer that produces a very fine spray, almost a mist, which will prevent any droplets from collecting on leaves and damaging them. It should be done in the morning so that the plants will be dry by nightfall.

A small pump-up (pneumatic) pressure spray does the job very well. The fine spray can easily be directed under the foliage as well as over the top. It is also possible with one of these to spray in situ such plants as Monstera, etc., without soaking the walls. The same type of pressure spray may also be used for pesticides.

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