Cattleyas As House Plants

Indoor orchid growers are divided as to whether cattleyas should be grown in an orchid case or without one. Actually a more important problem is whether the plants will receive enough light. They will do better in a fairly dry situation with good light, than in a humid condition without good light. Most homes are more dry than a greenhouse, and, feeling this lack to be serious, many indoor growers keep their plants too wet, both as to water in the pot and humidity.

When we first obtained an orchid case we put some mature and nearly mature cattleyas in it, thinking that they would do better than a group which had already spent a successful year on a window sill. To our surprise, those in the case did not do as well as those that were unprotected. The growths were softer and more slender, and came blind, that is, failed to flower. Studies with a light meter showed that plants in the case received considerably less light than those on the window sill, partly because they were farther back from the window and partly because the light had to come through two thicknesses of glass. The plants in the case had had a higher relative humidity than those in the window, but without enough light to make a good supply of food (sugar), they were unable to make as strong a growth and produce flowers.

It would seem from this (and we have seen many other such examples) that, if a case is to be used, it must be given a location with exceptionally good light, or the light must be augmented in some way. Otherwise, cattleyas will do better to be directly in a window.

Light

Plants in a house cannot have the long hours of light possible in a greenhouse. Therefore, the aim is to give them at least several hours of direct light, with the sun actually shining on the plants. The only danger in direct light is burning. The leaves absorb the light and raise their internal temperature to slightly above the temperature of the surrounding air. This increase of leaf temperature becomes dangerous when it approaches 100° F., and burning can occur when the temperature pushes above that.

In hot weather the difference between air temperature and leaf temperature leaves only a slight margin, and the burning point may easily be reached. A leaf burn has at first a scorched look, brownish-yellow and almost blistered, later turning dark brown and then black, and finally drying.

The morning sun is not so likely to build up the temperature to the burning point as is the afternoon sun coming through a west window. In a south window the sun from fall through early spring is not likely to burn the leaves, since temperatures are lower.

In all instances, to tell whether the light is too strong, watch the plants themselves. Feel the leaves when the sun is shining on them. If they feel hot to your touch, draw a piece of cheese-cloth or some other thin, wide-mesh material, across the glass for just the short period when the sun is pouring in. This will break the light but still allow the plants to have a generous amount. If the leaves feel just gently warm, not hot, let them have the sun straight. The leaves will be a light shade of green with good light, a dark green with less light.

In a greenhouse, too strong light will bleach the leaves to a yellow-green or yellow, but we doubt that plants in a home will receive this much light. However, it is good to know how to interpret leaf color in terms of amount of light, and if your plants should be turning yellow with too strong light, then use the cheesecloth shading during the brightest hours.

Some orchid growers are fortunate enough to be able to move their plants from one window to another to take ad-vantage of the best light during different seasons. In one home we know of, the plants are kept in an east window through late spring, summer, and early fall, and when the sun swings to the south in the winter, they are moved to a south window. Thus they have some direct sun all year round and make excellent growth and flowers.

Temperature. In speaking of temperature (and of any other environmental condition) we have to realize that the ideal cannot always be attained. Yet it is of value to know what the ideal is, in order to come as close to it as possible. Cattleyas do their best when they can have a night temperature of between 55° and 60° F., which we call “intermediate” in range. These moderately cool night temperatures allow the best growth to be made.

Control Night Temperatures

Higher night temperatures tend to deplete the food reserves of the plant, using food that should be saved for flower formation. In a greenhouse, the night temperatures can be controlled for the benefit of the plants, but homes are built and managed for the comfort of their human occupants. In a greenhouse, the temperature drops as the sun goes down.

In a home the furnace is not turned down until the occupants go to bed. Also, in a home the temperature does not fall as rapidly as in a greenhouse, and the plants do not have as many cool hours as they do in a greenhouse. However, conditions in general are less rigorous in a home than in a greenhouse - for instance, there are not the extremes of temperature, nor the need for as free ventilation in the summer to offset the long hours of sun heat.

With the more equable environment of a home, the plants seem to be able to tolerate night temperature a bit above what is considered ideal. This does not mean that night temperature should be ignored, for cattleyas will grow and flower more successfully the closer you can come to the ideal conditions. But it does mean that if you cannot furnish a place for them where the temperature drops to 55° to 60° F. at night, come as close as you can, and try to keep the temperature under 65° F. at night.

Summer day temperatures are tolerated pretty well by cattleyas, with the cooler mornings and evenings to make up for the hotter hours. In addition to burning, mentioned above, another danger of high temperatures is increased evaporation of water from the leaves. Cattleyas cannot make up extreme water loss as rapidly as garden plants, because absorption by the roots is not fast enough. The leaves do not wilt when dry, but over a long period the leaves and pseudobulbs become thin and some what shriveled.

It does not pay to pour more water into the pot if the fiber is already damp, although the plants will need more frequent watering in hot weather. A light syringing with a mist sprayer when the leaves are warm from the sun will help to make up for loss of water through evaporation. Not only will the plants absorb some of this water, but evaporation from their surfaces will help to cool them. The plants can be syringed in this way several times a day in hot weather, as long as you are careful not to wet the fiber too much and contribute to overwatering of the pot.

Part 2 On Cattleyas as House Plants

by Rebecca Northen

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