Houseplants In the Home
Naturally this question is not meant literally, but if we want to grow plants successfully then we must give some thought to providing the conditions that will satisfy their basic needs and keep them happy.
Plants grown indoors require approximately the same conditions as in their native environment. It is important that they be provided with a suitable growing compost, temperature, amount of light, and moisture (both in the compost and the 8 atmosphere). It is comparatively easy to provide the proper compost and regulate its moisture, but it is far more difficult to regulate the other factors which often require fairly complex equipment. Most amateurs who grow house plants are not able or do not wish, for instance, to install special fluorescent lighting or automatic misting equipment. Similar difficulties are posed by the problem of stabilising temperature fluctuations or heating the home to the temperature required for growing plants from lowland tropical regions.
One solution is a flower case with its own built-in lighting and heating, where one can grow even the most delicate and tender plants. If there is enough space it is often possible to provide congenial conditions for cold-loving plants by turning off the heating in one of the rooms. Otherwise take things as they are and select plants that will adapt to the given conditions.
One important thing that should not be forgotten, however, is that no factor acts independently of the others; all are interrelated. If, for instance, the light factor changes then it is necessary to adapt the temperature and watering accordingly. In general it may be said that there is a direct correlation between light and heat: if the intensity of light increases most plants require higher temperatures. Atmospheric moisture is often correlated with light indirectly. Here, too, temperature plays an important role. If the thermometer in a room with a temperature of n°C and relative humidity of 100 per cent registers a rise of 10°C (18°F), the relative humidity will decrease to a mere 55 per cent and vice versa, a 10° drop in temperature will cause the relative humidity to increase by approximately 50 per cent. From this it is easy to understand how plants with entirely different requirements can grow in the same locality in the wild. Picture a giant tree in the tropical rainforest: sunning itself at the top of the crown is a bromeliad and nestling at the foot of the trunk is a clump of ferns. In full sun the air at the top of the tree is often overheated and the humidity is very low; such a spot is occupied by bromeliads which are well adapted to dry conditions. The ground at the foot of the forest giant is naturally shaded, the temperature lower, and the relative humidity therefore higher. Thus, ferns can be cultivated in a shaded spot and sprayed over several times a day even at high temperatures whereas bromeliads would soon be destroyed by such conditions. In order to grow house plants successfully it is necessary to know not only their place of origin and the climatic conditions in which they grow in the wild, but also the type of situation they occupy in the wild.
Naturally there are exceptions to every rule and this is true also of plants. For instance, some species which flourish in mangrove swamps bordering river banks and tidal basins in the tropics (members of the genera Avicennia and Rhizophora) grow in full sun at high temperatures but are also happy in marshes or on flooded banks, in other words in an environment with a high relative humidity.
Let us return to the conditions of our homes. These are generally classed according to temperature into three categories: cool, semi-warm, and warm, characterized roughly by winter temperatures of 10 to 15°C (50 to 59°F), 14 to 20°C (57 to 68°F), and 15 to 25 or 30°C (59 to 77 or 86°F) respectively. Very cold homes are now becoming a thing of the past. Conditions for growing cold-loving plants are to be found only in conservatories, the hallways of some houses and foyers. Here it is possible to put to good use plants such as azalea,
Distribution of light in a room with a) windows facing south b) windows facing SW and NW c) windows facing NW and NE 9 bouvardia, cissus, clianthus,, , hedera, mikania, pelargonium and of the orchids Encyclia citrina, Coelogyne cristata and certain cymbidiums and odontoglos-sums. Most bulbs and tubers also do well in this sort of situation.
These temperate plants can be grown in warmer conditions as well. In warm homes one can grow practically all species of subtropical and tropical plants as long as their other requirements are met. In very warm conditions when the temperature rises above the desired level the room should be aired more frequently. Most plants, however, tolerate fairly marked temperature fluctuations for a brief period.
Another important factor for growing plants is light. Sunlight is necessary for the process known as photosynthesis to take place. During this process inorganic substances are transformed with the aid of radiant energy into organic substances that form the body of the plant.
The intensity of light is measured in lux, either by means of luxmeters or photographic light meters with a luxmeter scale. Lux is a unit of illumination equal to the illumination of a surface uniformly one meter distant from a point source of one candle. The intensity of sunlight in nature ranges from 0 to 100,000 lux, the first figure representing full darkness and the other full sunlight falling upon the earth at noon on a clear day.
It is difficult to determine exactly how much light is necessary for photosynthesis to begin. Also the amount differs according to whether the given plants are sun-lovers or shade-lovers. Photosynthesis usually takes place at a light intensity of as little as 100 to 1,000 lux. As the light intensity increases so does the rate of photosynthesis, up to approximately 10,000 lux. This data, of course, only serves as a guideline, for photosynthesis, just like any other process in living matter, depends on many other factors, particularly temperature.
Both maximum and minimum light intensity are harmful to plants if they are long-term, though we come across exceptions in both instances. Growing in the continual shade of the tropical rainforests require only minimal radiation for their life processes (often they are very sensitive to marked temperature fluctuations and lowering of the atmospheric moisture). In such forests the solar radiation in the treetops is close to the upper limit but the dense canopy reduces the amount of light that reaches the ground to a mere 1 per cent of full sunlight. Many bromeliads, growing as epiphytes in the uppermost reaches of such a forest, are adapted to these maximum values and need them for good growth the same as cacti, echeverias or sedums growing on sun-drenched rocks. With a little experience one can guess a plant’s light requirements by its appearance. Species with delicate, pale green or often blue-tinged foliage generally require shade. Plants whose leaves are thick-skinned and coloured red, violet or silvery can be put in full sun without hesitation. The general rule of thumb is that full sun is needed by most cultivated plants with decorative blossoms, succulents and stiff-leaved bromeliads. Permanently shaded situations are suitable for ferns with soft foliage and most selaginellas, also for certain species of fig, such as Ficus villosa, some members of the ginger family and of the genus Costus and for almost all species of plants in the seedling and juvenile stages. This again is determined by natural conditions, for most plants germinate and pass their early stages of development in the dense shade of other herbaceous plants, shrubs and trees.
How much light enters your home, and where is the best place to put plants? As an example, let us take a room 4 m 10 (13 ft) long with a large window taking up most of the space in the centre of one wall. Least suitable are the corners on either side of the window which are more deeply shaded than any other part of the room. Through the middle of the window to a distance of about 1.5 m (5 ft) the amount of full sunlight is 40 to 60 per cent. At a distance of about 2.5 m (8 ft) it is 20 to 40 per cent, whereas farther from the window it drops to a mere 15 per cent. The corners that are far from the window are not suitable places for plants because the amount of light penetrating there is only about 5 per cent of full sunlight. Much depends also, of course, on the aspect. Windows facing south, south-east and south-west provide the most light (60 to 80 per cent); where windows face north-west or north-east the amount of light penetrating the room rapidly decreases the farther the distance from the window. Plants requiring direct sunlight, in other words most flowering species, cannot be placed by north or north-west windows.
Almost all plants tolerate diffused light. Such conditions are readily recognized by moving the hand or some other object between the plant and the window; this should cast a distinct shadow on the foliage. However, the plant will call attention to its needs by itself. If it leans towards the light, has smaller, paler leaves and longer internodes (sections of stem between the leaves) then it should be put in a spot with more light.
Last of all, a few words about atmospheric andmoisture should be added. Soil moisture is regulated by watering. Some plants need to have their roots kept continually damp, the roots do not tolerate drying-out and the soil must be moist all the time. In the case of other plants the soil is allowed to dry out slightly before each thorough watering. A separate case altogether is hydroponics — the soilless cultivation of plants in clear nutrient solutions, anchored in inert material, such as siliceous gravel, sand or granules of various kinds. This website does not deal with the subject, but lists special literature where those who are interested can find more information. It should be noted, however, that most house plants do very well in such solutions and even species that are otherwise difficult to grow can be cultivated by this method.
How much and how often a plant should be watered depends on the plant’s origin, that is the amount of rainfall in its native habitat during the various months of the year, and on the temperature of the room. Water should be supplied in smaller quantities at lower temperatures and vice versa. This, however, is not a standing rule. Even in winter, when most plants need only limited watering,placed on the window-sill above a radiator must be watered daily, otherwise the soil will rapidly dry out and the plant wilt.
The atmospheric moisture in the modern household is usually low. This can be offset by means of various humidifiers, generally suspended on radiators, and sometimes also by syringing the plants directly with water. Many different types of syringes and misting equipment are available to choose from. Misting should be limited in winter and totally withheld in the case of plants from tropical or subtropical regions where the winters are dry. If several house plants are being grown then better moisture conditions will result by grouping them together on a table or in a large container where the evaporation from the soil surface will be greater. In the case of some tropical subjects from moist, humid regions it is impossible to provide the degree of moisture they need in the home and either we must do without them or grow them in closed plant-cases. There are comparatively few such instances; one, however, is the attractive pitcher plant (Nepenthes), which will grow but not form pitchers in dry surroundings.