Many gardeners put their house plants outdoors for the summer. In most cases it's not a good idea, according to Charles A. Conover, director of the University of Florida's agricultural experiment station at Apopka, which devotes itself almost exclusively to research on the problems of foliage house plants.
Indoors the plants usually receive rather low light intensity, to which they are adjusted. They have shade leaves. Shade leaves are generally (but not always) larger than sun leaves, thinner in the cross section, and able to make maximum use of low light energy.
If placed in full sun for even a few days, they will be severely damaged because of cell death due to high temperatures.
Plants grown in full sun have sun leaves; when placed indoors under low light they are unable to photosynthesize the food needed because they are very inefficient under low light. If the light difference is too great, the plant usually dies before it can adapt to the new environment.
Of course, the plants can be adjusted gradually to a change in the environment, but that may take several weeks. Then when they go back indoors, another adjustment is necessary.
But if the plant is obviously in poor health, due to inadequate light, it will often help to put it on a shaded porch where it will get better light but no sunlight.
What light intensity can the plants tolerate when you put them outdoors? That depends on the level they were receiving indoors. A plant receiving 50 to 75 footcandles indoors can tolerate 1,000 footcandles outdoors; 75 to 150 indoors, 1,500 outdoors; and 150 to 500 indoors, 2,000 outdoors.
Actually, you can hardly ever place them in full sun, Conover says, and in most instances they need to be in moderate to heavy shade.
Outdoors with higher light intensity and higher respiration rates, the plants will need to be watered more often.
A plant under fluorescent light can be moved to an east window where it does not receive direct sun, Conover says; also a plant directly in front of a south window can be moved to a spot on the terrace where it receives only early-morning sun or partial shade all day. Q: Aphids (plant lice) did a lot of damage in my garden last summer. Is there any way to control them without spraying with poisonous chemicals ? A: Research has shown that a spray of soap and water (Ivory liquid dish-washing detergent is good, about 2 percent) provides fair control. Also, alumninum foil placed on the soil around plants repels them and thus delays the spread of aphid-borne plant diseases. The .0015" gauge is the most practical, but a thicker gauge, .004", can be used for two or three years. Q: Would it improve my tomato crop if I could put a hive of bees near them when they are in bloom ? A: There are three kinds of flowers -- male, female and perfect. Perfect flowers have both male and female organs. Tomatoes produce perfect flowers and only, and the bees would be of little help. Q: Our yard is mostly shaded by trees. We'd like to grow some flowers; are there any that would bloom without much sunlight ? A: While many flowers require at least four hours of sun for best blooms, there are some that will grow and bloom well in shaded areas. This includes bleeding heart, primrose, daylily, Japanese and Siberian iris, English daisy, pansy, wax begonia, coleus, flowering tobacco, impatiens and lobelia. Q: Mushrooms are appearing in our lawn; can they be eaten ? A: Poisonous species grow side by side with edible ones, and there is no simple test to distinguish one from the other. One person may eat a certain mushroom with no ill effects while another may have severe nausea and intestinal distress, according to specialists. They do not infect or cause disease on grass plants; they live on the organic matter buried in the soil, such as wood, stumps, etc. As these materials decay, the mushrooms (fungi) grow more readily. Q: My candytuft is 10 to 12 inches high and going to seed. Can I cut the stems back to ground level ? A: The best treatment is to cut them back to about six inches with hedge shears immediately after the flowers fade. If this is not done, too much energy is spent by the plant in seed production for good subsequent growth and flowering. Q: I was given some flowers at the office one Friday and took them home. They were beautiful. Saturday morning I cut the stems with scissors, and put them in cold water; on Sunday they had begun to fade. There had to be something wrong somewhere. Can you help me ? A: Cutting the stems was a good idea, but it should have been done as soon as you got home -- and with a knife, not scissors. Scissors pinch the stems, reducing their ability to absorb water. Use tepid water, not cold water, because flowers absorb warm water more easily. The cooler the room temperature, the longer the flowers will last. Q: My favorite English hawthorn gets spotted leaves every year and in a few weeks they dry up and drop off. Is there a way to prevent it ? A: English hawthorns may lose most of their leaves during the summer because of leaf blight. The disease overwinters on fallen leaves and in small crevices in the bark. The same disease also affects pear and apple trees. One of the best materials with which to spray is Acti-dione, sold as Actispray. Make three applications at 10-day intervals, the first in the spring immediately after leaves unfold. Directions on the label for mix and application should be followed closely.