1. Routine Treatment of House Plants

Many species of plants, which were formerly regarded as hot-house subjects, have in recent years become popular for indoor decoration. Although some of them are native to the tropics, they may be acclimatised and can be grown indoors in temperate countries with confidence.

The beginner in the cultivation of house-plants should, however, proceed with caution. Some plants are more capable of with­standing a dry, hot atmosphere than others, and these should be chosen first, in order that experience may be gained in plant culture.

Generally, plants which have thick, leathery foliage respond best to room conditions. The reason for their ability to withstand the unfavourable conditions of living rooms is that the leaves are tough in texture and in some species they are so constructed that transpiration is reduced to a minimum. Transpiration, the loss of moisture by the leaves, may be slowed down in these plants by devices such as sunken stomata (breathing pores) and thick cuticle (outer skin). The Christmas cactus (Schlumbergera), Sansevieria and Hoya are typical examples of such plants. Other plants, such as the maidenhair fern, Coleus, Cyclamen and Fuchsia, have thin leaves which give off moisture very rapidly and are not so easy to cultivate in rooms. These plants grow best in a moist atmosphere, but this is not easily provided in rooms, and attempts made to maintain a moist atmosphere are detrimental to the furnishings of the rooms.

It Pays to Acclimatise the Plants

Whenever possible, the plants should be obtained after artificial heat is no longer required. They are then not subjected to fumes from the fire and can be given plenty of fresh air, which will harden the developing foliage and prepare the plants for the unfavourable conditions of the dry atmosphere of heated rooms.

Many people, however, receive Christmas gift plants, such as Primula obconica, Azalea, Erica (heath) and Begonia Gloirc de Lorraine. The beauty of these, however, is usually very short­lived, because the plants have been raised in a moist atmosphere and are, therefore, too tender to withstand the hot, dry conditions of living-rooms.

Cool atmosphere needed

To keep house plants in a fresh condition, they must be set in as cool a place as possible. An unheated room is best, provided the tem­perature does not fall below 45° F. During very cold nights the plants may be brought into a warm room, but kept well away from any heating ap­paratus, and removed to the unheated rooms as soon as the temperature rises sufficiently in the day. Permanent large plants, which cannot be moved about easily, can be protected during cold spells by covering them "with several thicknesses of newspaper. When outside conditions are pleasantly warm —that is, when you find it Fig. i. Sponging the leaves of Aspidistra congenial to be out of doors with a weak solution of insecticide yourself—the plants may be placed outside and syringed with clear water to cleanse and freshen them, as it is important that the pores of the leaves should not be clogged by dust particles. At the same time, the soil should be well moistened and the leaves sponged (broad-leaved plants such as Aspidistra; Fig. i). The plants are then returned to the living-rooms. During light, warm showers it is always beneficial to set the plants in the open (except those in flower) for short periods.

The Problem of Watering

It is not easy to decide how often plants should be watered. The amount of water which a plant can use depends on the rate at which it is absorbed.

It is evident that a plant in active growth uses more water than when it is dormant or semi-dormant, and plants which have completely filled their pots with roots require more frequent watering than those which are not well established.

The time of the year must also be taken into consideration. During the growing season, from April until October, the majority of pot plants use up more water than they do in the rest of the year. There are, however, exceptions, such as forced bulbs of hyacinths and Narcissus, as well as late-flowering Chrysanthemums, Cyclamen and species of Erica.

Testing the Moisture Content of the Compost

Pot plants should be watered when the compost is moderately dry and should then be given sufficient water to soak right down to the drainage hole. Frequent dribbles are useless, because the water does not reach the compost at the bottom of the pots where the majority of the feeding roots are situated.

The problem for the beginner is to know when the compost is dry enough to need watering. The best test is to tap the pots about half-way down with a wooden hammer or the knuckles of the hand. If a light hollow sound is emitted, water is needed, but when a dull noise is heard, water is not required. The exception to this rule is when the compost has not been packed firmly into the pots, in which case the pots when tapped will sound hollow at all times. Rain water is always best for the purpose, but tap water is not usually detrimental. It should be of the same temperature as that of the room in which the plants are growing.

Signs of Overwatering

Except for some semi-aquatic plants, such as Cyperus alternifolius, it is quite easy to overwater, with disastrous results.

Many plants, especially those with soft active shoots and leaves, such as species of Primula, become chlorotic at the tips, turning a sickly yellow colour. As soon as this is noticed, watering must cease, and the soil should be pricked over with a pointed stick, to aerate it. No more water should be given until the compost becomes quite dry.

Compost which has been overwatered quickly becomes covered with a surface of moss or algae; this coating must be removed to aerate the compost. Species of Azalea and Erica (heath), however, must not be given tap water, as this causes the shoots to become chlorotic (turn yellow). Instead, rain water should always be used.

The Watering Routine

When house-plants are grown in pots, they must be inspected daily to determine their need for water, because the soil in the pots of some plants will dry out every day, whereas other pots may remain moist for several days.

The pots may be set in saucers or bowls to catch the drainage water. Glazed containers are the best if the plants are to stand on polished tables. Unglazed containers will allow the moisture to seep through and cause damage to the woodwork or other materials of which the tables, shelves or ledges are constructed.

Plants standing in saucers set in hanging baskets are very ornamental but it must be remembered that they need to be taken down daily for watering and for emptying the saucers; this may take up a considerable amount of time if many plants are grown.

Feeding the Plants

Plants which are well rooted and growing freely need the greatest feeding. In most cases, this extra nourishment is required during May to August; but plants such as forced bulbs of Narcissus, tulips and hyacinths benefit from watering with liquid manure or fertilisers from the time the flower buds begin to swell. The easiest method of providing the extra nourishment is to use 'Plantoid' tablets, according to instructions supplied with the product. 'Liquinure', a liquid fertiliser, is also to be recommended.

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