FIG. 66.
Seedling radishes reaching for light.[ToList]
FIG. 67.
Elm leaves injured by the "imported elm-tree leaf beetle," a chewing inject.[ToList]
The work of the leaves of house plants is often interfered with by not giving them sufficient sunlight. Garden and field plants are sometimes planted so thick that they crowd each other and shut the light and air from each other, or weeds are allowed to grow and do the same thing, the result being that the leaves cannot do good work and the plant becomes weak and sickly. Weeds are destroyed by pulling them up and exposing their roots to the sun. This should be done before the weeds blossom, to prevent them from producing fresh seeds for a new crop of weeds. Some weeds have fleshy roots—for example, dock, thistle—in which food is stored; these roots go deep in the ground, and when the upper part of the plant is cut or broken off the root sends up new shoots to take the place of the old. Some have underground stems in which food is stored for the same purpose. The surest way to get rid of such weeds, in fact, of all weeds, is to prevent their leaves from growing and making starch and digesting food for them. This is accomplished by constantly cutting off the young shoots as soon as they appear above the soil, or by growing some crop that will smother them. The constant effort to make new growth will soon exhaust the supply of stored food and the weed will die.