How to Look After House Plants
Until just after the Second World War, palms,, aspidistras and a few seasonal flowering pot plants were the only plants available for interior decoration. Now, however, there exists a wide range of foliage pot plants grouped under the heading of house plants.
This change is due chiefly to the architects who designed post-war buildings on such simple and sometimes severe lines. The introduction of house plants in a wide variety of form and colour provided both a new type of decoration with which to relieve the architectural simplicity of the home, and also a new form of art in the arrangement of house plants. Thanks to improved lighting and heating, many varieties formerly known strictly as conservatory or hot-house plants will now thrive as house plants. The kinds that are easier to grow will last for several years.
CHOOSING HOUSE PLANTS
When choosing plants, consider first their shape, habit, texture and colouring in relation to the position they will occupy and in relation to each other. For a group of plants, choose a tall specimen to give height, a climbing variety, several bushy varieties, and the trailing variety to cascade over the edges of the container. Aim also for good contrasts of leaf shape and colour, choosing the fresh and subtle green-leaved varieties for single specimens in key positions. Use multiple wall-brackets rather than the type that holds a single plant, to allow scope for grouping and contrast.
The next consideration is the temperature of the room in which the plants are to live. If the night temperature falls to between 45 and 50° F. (7 and 10° C), choose only the tolerant kinds. If the minimum night temperature can be maintained at 50 to 60° F. (10 to 16° C), intermediate plants may be used, and at higher night temperatures the delicate varieties as well.
Humidity is linked with temperature. The amount of moisture in the air is relatively greater at lower temperatures. Modern heating provides good warmth but often dries the atmosphere. It is important, therefore, to keep all plants out of range of radiation from a source of dry heat, such as a gas or electric fire or a coal fire. Never place a plant directly above a source of dry heat such as a radiator or convector. All house plants prefer humidity, and the delicate ones must have it to grow and thrive. Naturally a home cannot be turned into a steaming jungle, but plants can be helped in many ways without interfering with personal comfort.
An easy way to provide humidity is occasionally to spray over the leaves with tepid water, using an old scent spray or something similar. Sponging the leaves, both above and below, with tepid water and a clean sponge is equally effective. Fresh air is not essential to house plants, but opening the windows on a mild, damp day will serve the dual purpose of raising humidity and dispersing harmful gas or oil fumes. Always avoid draughts.
Another means of providing humidity is to place a layer of small pebbles or shingle in the bottom of a shallow tray or saucer about l in. deep. Fill this with water to just below the surface of the pebbles and stand the plant in its pot on the pebbles. When the plant is watered, the surplus will drain through to the pebble base, later evaporating to create the humid “micro-climate” the plant needs. Take care that the plant does not stand with its feet in water.
The best method of providing and conserving humidity is to group the plants in a container, A metal-lined trough or pottery bowl makes a good container, or, for those who prefer something a little more unusual, a deep copper pan or antique container can be used. Fill the container with moist peat, and plunge the plants into the peat up to the rim of their pots. Keep the plants in their pots so that they may be fed and watered according to their individual requirements.
Keep the peat in the container moist. The moisture will then evaporate slowly, forming a humid “micro-climate” round the plants, which will tend to form an umbrella of leaves over the peat to prevent the moisture from evaporating too rapidly. To provide humidity for a single plant, find a container with a larger diameter than that of the pot and pack moist peat in the space between the two.
Light is an important factor regulating plant growth, and the closer natural conditions can be simulated, the greater will be the success in growing house plants. Many varieties originate from the floors of great tropical forests, where the sunlight is filtered through the canopy of branches and leaves overhead. Most house plants, therefore, prefer shade or semi-shade. In winter, the deciduous forest trees shed their leaves, and more, though less intense, light reaches the floor of the forest. In winter, therefore, when the days are short, house plants need all the light they can get, and during the day should be moved nearer to a window.
Generally speaking, the green-leaved plants prefer a shaded position, and many will tolerate quite dark corners. The coloured-leaved or variegated varieties require more light to preserve their leaf colour, but no house plant, with the exception of Sansevieria trifasciata laurentii (mother-in-law’s tongue), can withstand long periods of direct sunlight. A south-facing window is therefore not an ideal position for house plants, unless the sunlight is filtered by net curtaining or a Venetian blind. Conservatories or greenhouses containing house plants should be heavily shaded in spring and summer as a protection against strong sunlight; remove all shading, however, during the autumn and winter. Where the shading is of the type that is sprayed on to the glass outside, it should be renewed after heavy rainstorms.
A photographic light meter can be used as a means of checking the intensity of light reaching the leaves of house plants. On a Weston light meter, with bright summer sunlight outside giving a reading of 22, a reading of 12 to 14 in the greenhouse or home is ideal for most green-leaved varieties, 14 to 16 for the coloured-leaved and variegated varieties, and 9 to 10 for varieties that need heavy shade. These readings are intended only as a simple guide, and do not provide the high degree of accuracy that would be required by scientists.
Artificial light as yet plays little part in plant growth indoors, although experiments with special lighting bulbs are being carried out.
Correct watering is of supreme importance, and largely determines success or failure with house plants.
There are no cheap or readily available instruments for measuring the water content of thein the pot, and the practical methods used by gardeners and horticulturists should therefore be relied upon. With experience, one can quickly tell from the weight of the pot whether the soil is wet or dry, but a sharp rap on the side of the pot with the knuckles will confirm this. If the sound produced is a hollow ringing tone, the soil is dry; if it is only a dull thud, the soil is wet. This method can only be applied to clay pots. If the plant is in a plastic pot, the difference in weight between wet and dry is more apparent.
Another method of checking is to observe the colour of the surface soil. When wet, it is black or dark in colour; when the soil dries out, it becomes a greyish-white.
The last method is by touch. By pressing the tips of the fingers into the top-soil one can learn whether it is wet and soggy, moist, or hard and dry, by the resistance offered by the. The two extremes of wet and dry soil should always be avoided, the ideal being an intermediate, evenly-moist condition.
The amount of water required by house plants changes with the season, and even between one home and another. During the period of vigorous growth in spring and summer, house plants require plenty of water, and the soil should not be allowed to dry out too much between waterings. In autumn, when growth slows down, watering should be reduced and care should be taken not to over-water. Throughout the winter, particularly during cold weather, the greatest care should be taken, as the plants have almost ceased to grow. In this semi-dormant period, allow the soil almost to dry out between waterings, and then give only sufficient water to maintain life, moistening the soil without making it wet. The golden rule at all times, particularly in winter, is never water when the soil is wet. Make a practice of watering early in the day, and drain off all surplus water before replacing the pot in position. Soft water is always preferable but not essential.
In winter, water the intermediate and delicate varieties with tepid water (at room temperature: about 70° F. or 21° C). This treatment will benefit the easy varieties also. Cosseting house plants in winter, which usually means over-watering, often has fatal results. Neglecting them will do far less harm.
Where the room temperature drops sharply at night during cold weather, always remove a plant that is moist or wet to a warmer position. Plants left on window sills, between the curtains and the window, are in great danger of being damaged or killed by frost. Always bring them into the room at night.
Drooping of the leaves is usually a sign of excessive dryness. Never follow a period of dryness with heavy watering, as this can cause the loss of the lower leaves, but return gradually to normal watering.
Black or brown wet patches on the leaves or stem are often a sign of over-watering in winter. If the lower part of the stem is affected fatal results may follow. If the leaves are affected, keep the plant almost dry for a while. Some leaves will certainly fall, but the life of the plant may be saved.
Before going away for any lengthy period in spring or summer, water all house plants thoroughly. Insert two small stakes in each pot, slightly taller than the plant, one at each side of the pot. Slip a polythene bag over the stakes and secure it to the pot with a rubber band. Place the plants in a position where they will not be exposed to strong sunlight. Moisture will then evaporate from the leaves, condense on the walls of the polythene bag and run down to the bottom of the bag, where it will be absorbed by the pot again.
The plants will be in an ideal atmosphere, with humidity and a simple self-watering device, which could be described as a miniature greenhouse.
Feeding is beneficial during the period of active growth from spring through summer to early autumn. In late autumn and winter, discontinue feeding altogether.
There are many good brands of house plant fertilizer available from florists or horticultural nurserymen. Always follow the maker’s instructions, for exceeding the stated dosage will only harm the plants. The small bottles of liquid fertilizer are perhaps the most convenient to use in the home. A few drops in water, according to the manufacturer’s instructions, will ensure adequate feeding when watering.
A trap into which many inexperienced house plant enthusiasts fall is that of attributing the unhealthy appearance of a plant to starvation. Try to determine first whether the symptoms are due to damage by cold, over-watering, or excessive dryness. If these possibilities can be excluded, and if the roots are healthy and undamaged, then feed the plant, but remember that feeding a sick plant will make it worse.
Pale green leaves usually indicate the need for feeding, particularly if the plant is pot-bound (the pot being full of roots).
Frequent repotting of house plants is quite unnecessary, and generally plants can stay in the same pots for 12 to 18 months. Most kinds will thrive in pots that appear too small for them, and plants that have filled their pots with roots will live on happily if they are fed regularly.
Late spring or early summer is the right time for repotting, as the roots then have time to become established in the new soil before the cold weather sets in.
Top-heaviness should be the main indication for repotting, but before repotting, inspect the ball of soil. This can be done by spreading the fingers of one hand on either side of the stem between the lower leaves and the top of the pot. Invert the pot, and tap the rim sharply two or three times. The soil ball will then fall out into the hand.
If the roots are obviously overcrowded or tangled round the outside of the soil ball, repotting into a one-size larger pot will be necessary. Cover the drainage hole of the larger pot with crocks, put some potting compost in the bottom, stand the soil ball in the centre, then fill up with potting compost and firm down.
If repotting is unnecessary, drop the ball back into the same pot and tap the base sharply once or twice. The plant should then be firmly in place, but if it is not, firm the soil with both thumbs.
As a general potting mixture a John Innes compost with the addition of one-third part by volume of peat or leaf mould is recommended. This is a good standard compost available from most florists and horticultural nurserymen, but any peaty compost will suffice as long as it has an open texture.
A good-potting compost, suitable for most house plants, can be made from: 2 parts turfy loam, 1-1/2 parts leaf mould, 1 part washed sharp sand, 1/4 part farmyard manure, 1/2 part peat. (All parts by volume.)
The reaction should be slightly acid with a pH of 5-1/2 to 6. Add superphosphate at the rate per bushel recommended by the suppliers.
The potting mixture and the pot ball of the plant should be just moist. Water sparingly for a few weeks to encourage the roots to grow into the new soil.
Never repot a sick plant whose roots have been damaged by cold or bad watering, as this is the surest way to kill it.