Insects and Insecticides: Insects are the pest of house plants. The worst of them are plant lice, mealy bugs, white and black flies, red spider, and the various scales. All are fought with pretty much the same weapons—namely, soap and water, smoke, and eternal vigilance. Greenhouses and hothouses are almost universally infested. Hence every new plant must be suspected. Do not set it among other plants clean and thrifty for at least a fortnight, and then only after a thorough bath. A plant badly infested had better be thrown away, and quickly. Flies white and black are hardest to fight; they fly away at a touch on the pot. Set the infested plant apart, with a stick standing higher than itself fast in earth, throw a thin cloth over, letting it reach the ground all around, then slip under it a lighted smudge, and set over cloth and plant either a box or a barrel, with paper pasted over the cracks. Let stand two hours, then plunge in a tepid bath, keeping on the cloth until well under water. This to hold in any flies left living. Splash well, drain, and while damp dust with either insect powder or finely crumbled tobacco, putting it on both sides of the leaves.
For plant lice spray thickly with strong tobacco water, leave an hour, then bathe, and dust with more tobacco. A little flowers of sulphur mixed in makes the treatment more effectual. Bathe in suds (carbolic soap, if possible) next day, and follow with a clear tepid shower.
Red spider is invisible until it appears as red blotches upon foliage. Water, and still more water, combined with smoking cures it. Shower infested plants heavily every day for a fortnight, smoke with tobacco twice a week, and keep well dusted with either tobacco or pyrethrum powder. Mealy bugs, which are white and woolly, as big as grains of wheat, should have a sulphur dusting after smoking and bathing. All the big scales, which are never very numerous unless plants are fatally neglected, should be hand-picked, then the plant well washed with whale-oil soapsuds dashed with carbolic acid. San José scale, which is almost invisible but feels like fine rough sand upon the under sides of leaves and over stalks, is so deadly and difficult any plant found infested should be burned at once, the pot broken, and the earth soaked with boiling water. Cures for it there are, but too difficult for amateurs, withal somewhat dangerous.
Buy tobacco dust, make tobacco water. Pour a gallon of boiling water upon a pound of tobacco stems, let stand a day, keeping warm, strain and use. Cut the spent stems fine and mix through potting soil. Enough tobacco water to color it mixed in makes a plunge bath more effective against insects. Make smudges thus: put a few slivers of wood or half a dozen matches crossed in a small flat tin, cover with either pyrethrum powder, tobacco dust, cut up stalks, unspent, or flowers of sulphur mixed with fine damp sawdust. Light, see that there is not too much blaze, and set beneath plants. Do not make smudges big enough to give out scalding heat; better two or three small ones if heavy smoke is required.
Red rust and brown scale, the special enemies of palms, need to be washed off with strong carbolic soapsuds and a soft brush before bathing and smoking.
Earth Worms: Lime water is the remedy for earth worms. Stick holes in the earth quite to the bottom, then pour on clear lime water (see section Renovators) till it stands on top. The worms will crawl up to escape it. Lime water is also good to sweeten sour earth. Give a half cup after the hot-water treatment. Dig up the earth in pots so as to keep a light, clean surface. Green scum, while not dangerous, does not make for plant health.
For Roaches, dip cut potatoes in arsenic mixed with sugar and lay cut side down on the pots and about them. Gather up every morning, dropping instantly into a vessel of boiling water—this to destroy such insects as remain alive. But never put out poison if there are children in the house.
Cuttings: Cuttings root best in clean sand, kept very wet and warm and under glass. Make the cuttings of new wood, neither soft nor fully ripe. Cut with at least two eyes—three are better—slant cuts, and set in sand slantwise, with one eye above the surface. Shift as soon as growth begins fully to thumb-pots, and keep the pots plunged in another box of sand. Make geranium cuttings, whether scented or flowering, of healthy stalks full of sap and vigor. June is the best time to make cuttings of lemon verbena, fuchsia, heliotrope, and roses. Tips of strong shoots from either fuchsia or heliotrope will root then almost for the chance. Chrysanthemums from cuttings of the flower stalk give much finer bloom than those from old roots.
Leaf cuttings are interesting. Tuberous begonias root thus readily. Roses are more difficult. Peg down the leaf on wet sand under glass, make tiny cuts in it, and keep very wet in sunshine. Roots will strike from the cuts after they have calloused.
Summing up, the needs of a house plant are the same as those of a human being—air, light, food, water, cleanliness, and love.