HOTBED. A Hotbed is a frame or box which has artificial heat and a transparent covering and in which plants are grown. It differs from a coldframe (which see) in the fact that it has artificial bottom heat.

This bottom heat is usually supplied by fermenting organic matter, chiefly horse manure, but hot air, hot water or steam conveyed in pipes, may be employed. It is covered with sash of which the normal or standard size is 3 feet wide and 6 feet long. These sashes are laid crosswise the box or frame. The standard size of frame is 6 feet wide and 12 feet long. A "frame," therefore, accommodates four sashes. However, the frame may be of any length desired. This frame is ordinarily made of boards, and the back of it is 3 or 4 inches higher than the front, so that the sashes slope to the sun. It is customary to have a space of 6 to 10 inches between the earth and the sash on the lower or front side. The manure which is used to heat the bed may be placed on top of the ground and the frame set on the pile, or it may be placed in a pit. If the land is warm and well drained, it is ordinarily better to have a pit from 1 to 2 feet deep and to set the frame over it. This is especially the case if it is desired to have a permanent Hotbed yard. The place in which the frames are set should be protected from the cold and prevailing winds by a rising slope, a high board fence, a building, hedge, or other obstruction. If the frame yard is near the main buildings, it will be much more accessible in rainy or snowy times, and the plants are likely to have better care. Water should also be handy.

[Illustration: Section of a Hotbed]

The time of starting a Hotbed will depend upon the kinds of plants to be grown, the amount of time which one wishes to gain, and something, also, on the quality of the manure. The hardier the plant the earlier it can be started. In the latitude of New York, from the first to the middle of March is the usual time for starting a Hotbed. In this bed are sown seeds of early flowers and such vegetables as cabbage, cauliflower, tomato, etc. In the raising of any plants in the Hotbed, it is very essential that they do not become "drawn" or "leggy." In order to prevent this, they must be given plenty of room, thorough ventilation on all pleasant days, and not too great heat. It is well to transplant them once or twice before they are finally set in the field, especially if they are started, in New York, as early as the first or middle of March.

When they are transplanted, they can be set in another Hotbed or in a coldframe; but it is important that the succeeding frames in which they are set should not be very much colder than the one in which they grew, else they may become stunted. It is well, however, to transplant them into a gradually cooler and freer atmosphere in order to harden them off, so that they may go into the open ground without danger. On every pleasant day, raise the sash at the upper end 1 or 2 inches, or if the sun shines brightly and the wind does not blow, give even more air; and eventually strip off the sashes entirely. It is very important that the plants are not kept too close and grown too soft. It is usually advisable to sow cabbage, lettuce and other hardy plants in different frames from tomatoes and other tender things, in order that the proper requirements may be given to each. At night the Hotbeds (at least early in the season) will need more protection than the glass sash. It was formerly the custom to use thick rye-straw mats to cover Hotbeds, but it is now a common practice to use the straw matting which can be bought of carpet dealers. This is rolled out on the sashes at night in one or two thicknesses; and if the weather is sharp, board shutters, the size of the sash, may be laid on top. As the manure heat begins to fail give more and more air, so that the plants may be able to shift for themselves when the bottom heat is finally exhausted.

Fresh horse manure is the material which is commonly used for the heating of Hotbeds. If it can be secured from livery stables, so that it is all of nearly or quite the same age, better results may be expected.

Manure from highly fed horses usually heats better than that from horses which receive little grain, or in which there is very much litter. Put the manure in a pile, preferably under cover, and as soon as it shows signs of heating, fork it over in order to mix the entire mass and to cause it to heat evenly. When it is steaming throughout the whole mass, it may be put in the bed. Assuming that the Hotbed has a pit beneath it, it is well to put in 2 or 3 inches of coarse litter in order to keep the manure off the cold ground. The manure is then put in and tramped down, in layers of 4 to 6 inches each. If the manure is of the right consistency, it will pack without becoming dense and soggy; that is, it will spring a little beneath the feet. If it has too much litter, it will fluff up under the feet and not pack well. From 18 to 24 or even 30 inches of manure is placed in the pit. On top, an inch of dry straw or light leaf-mold may be placed to serve as a distributor of the heat to the earth above. From 3 to 4 inches of rich, light earth is placed upon this, in which to sow the seed. The manure will ordinarily heat violently for a few days. Place a soil thermometer in it, and as soon as the temperature begins to fall below 90 the seeds of tomatoes and egg-plants may be sown; and when it begins to fall below 80, the seeds of cabbages, lettuce and cauliflower may be sown. If the frame is not placed over a pit and the manure is put on top of the ground, it will be necessary to allow the body of manure to project 1 or 2 feet in all directions in order to prevent the edges of the bed from freezing.

In starting plants in a Hotbed, one must not expect to gain as much time in the crop as he gains in the starting of the seeds: that is, if he starts the seeds two months ahead of the normal season, he will not gain two months in the ripening of the crop. Ordinarily, he cannot expect to gain much more than one-half the time, particularly if the plants are transplanted to the field from the Hotbed.

Some plants may be grown to maturity in the Hotbed, particularly lettuce and radishes. After Hotbeds have been emptied of their plants, the sashes may be stored away, and the frames, with their spent manure, used for the growing of an early summer crop of melons or cucumbers.

HOUSE PLANTS. See _Window-Garden_.

[Illustration: Hyacinth bean]

HYACINTH BEAN (_Dolichos Lablab_). A very rapid-growing twiner, bearing fragrant flowers of purple or white. It is a fine screen plant. Plant seeds when the ground is warm where the plants are to grow; or they may be started early in pots. Height 10 feet.

HYACINTHS are most popular winter- or spring-flowering bulbs. Hyacinths are hardy, but they are often used as window or greenhouse plants. They are easy to grow and very satisfactory. For winter flowering the bulbs should be procured early in the fall, potted in October in soil composed of loam, leaf-mold and sand. If ordinary flower pots are used, put in the bottom a few pieces of broken pots, charcoal or small stones for drainage; then fill the pot with dirt, so that when the bulb is planted the top will be on a level with the rim of the pot. Fill in around the bulb with soil, leaving just the tip of the bulb showing. These pots of bulbs should be placed in a cold pit, cellar or on the shady side of a building. In all cases, plunge the pot in some cool material (as cinders). Before the weather becomes cold enough to freeze a crust on the ground, the pots should have a protection of straw or leaves to keep the bulbs from severe freezing. In from six to eight weeks the bulbs should have made roots enough to grow the plant, and the pots may be placed in a cool room for a short time. When the plants have started into growth, they may be placed in a warmer situation. Watering should be carefully attended to from this time, and when the plant is in bloom the pot may be set in a saucer or other shallow dish containing water.

After flowering, the bulbs may be ripened by gradually withholding water until the leaves die. They may then be planted out in the border, where they will bloom each spring for a number of years, but will never prove satisfactory for forcing again. The open ground culture of Hyacinths is the same as for tulips, which see. See _Bulbs_.

_Water Culture of Hyacinths._--The Hyacinth is the most popular of the Dutch bulbs for growing in vases. The Narcissus may be grown in water, and do just as well, but it is not as pretty in glasses as the Hyacinth.

Glasses for Hyacinths may be had of florists who deal in supplies, and in various shapes and colors. The usual form is tall and narrow, with a cup-like mouth to receive the bulb. They are filled with water, so that it will just reach the base of the bulb when it has been placed in position in the cup above. The vessels of dark-colored glass are preferable to those of clear glass, as roots prefer darkness. When the glasses, or bowls as above mentioned, have been arranged, they are set away in a cool, dark place to form roots like potted bulbs. Results are usually secured earlier in water than in soil. To keep the water sweet, a few lumps of charcoal may be put in the glass. As the water evaporates, add fresh; add enough so that it runs over, and thereby renews that in the glass. Do not disturb the roots by taking out the bulb.

HYDRANGEA. One of the commonest lawn shrubs is _Hydrangea paniculata_.

The commonest fault in growing it is scattering the plants over the lawn, where they suffer in the competition with grass roots, and do not show off to advantage. It is far better to mass them in front of taller things. The Hydrangea blooms on wood of the season; therefore it should be pruned after bloom--in winter or early spring (see _Pruning_). Cut back heavily, in order to secure the strong new shoots upon which the flowers are borne.

HYSSOP. See _Sweet Herbs_.

ICE PLANT, or MESEMBRYANTHEMUM. Fine little plants for rockwork or edging. The majority of the species are greenhouse and window plants, but a few can be recommended for outdoor planting. A very sunny location, with gravelly soil, will give the best results, either in the open or in the house. Easily propagated by pieces of the plant laid on moist sand in a somewhat sunny place. The common Ice Plant of window-gardens is readily grown from seeds or slips. It is prized for its glandular-glistening thick foliage (whence the common name). The little flowers, which open in sunshine, are also interesting.

IMPATIENS SULTANI is a generally known conservatory plant, making a charming pot subject for warm greenhouse or a room. It is readily propagated from seed or cuttings, seed being preferable. Flowers bright pink-red. Of easy culture in a fairly moist atmosphere. Height about 18 inches.

INSECTS. For horticultural purposes, Insects might be grouped into three general classes: borers, or those which live inside the plant tissue; chewing Insects which live on the outside of the plant; and the sucking Insects.

As a general statement, it may be said that the digging out of borers is the only complete remedy. Sometimes an application of something to the body of the tree may keep them out, but it is always uncertain; and it usually involves more work than to dig them out. All trees which are subject to borers (especially apples, peaches and pears) should be examined at least twice every year. See _Borers_.

[Illustration: Moth of one of the borers]

[Illustration: A beetle borer]

The general run of chewing or biting Insects may be killed by the arsenical poisons. Such Insects are the common types of worms and beetles which feed on foliage. The leading poison which is now used for this purpose is Paris green (which see). Hellebore and pyrethrum are useful when it is not advisable to use arsenical poisons.

The sucking Insects include all the kinds of plant lice, the squash bug and all the scale Insects. These are dispatched by some material which kills by external application, especially material which has kerosene or petroleum in it. The common material heretofore used for this purpose is kerosene and soap emulsion; but it is now believed that the emulsion of kerosene and water is fully as efficient, and since machines have been perfected for automatically mixing it, it is a much more practicable remedy. See _Kerosene Emulsion_.

[Illustration: Weevil--a chewing insect]

In the fighting of all Insects, success depends upon taking them in time. If something is known of the life history of the Insect, very much will be gained, for the operator may be on hand as soon as the Insect is expected to appear.

_Insects on House Plants._--The most troublesome or common Insects with which the amateur is likely to meet in the window-garden or conservatory are the red spider, mite, mealy bug, aphis, and scale.

The red spider is a very minute Insect with a reddish body. Its presence may be suspected whenever plants are growing in a warm and dry place.

Usually it first appears on the under side of leaves, but it multiplies rapidly, and will soon not be so choice of position. It sucks the juices of the leaves, and they soon indicate the injury by a dull appearance, and also, in many cases, by small whitish or paler areas on the upper surfaces. The mite is of similar habits and size, but is of a pale color, with black on its back. It appears under the same conditions as the red spider. These pests are small, but are very serious if allowed to multiply unchecked. They should be looked after as soon as their presence is detected.

The remedy is to arrange for keeping the air about the plants more moist, and giving drenchings of the foliage with clear or soapy water.

The latter is most effective. The soap used may be simply the common washing soap, or that sold at drug stores known as whale-oil soap. In fighting them, care must be used not to keep the soil soaked with water, or it will check the plants in vigor and only add to the strength of the enemy. Even florists sometimes get into just such a predicament.

Flagging and extreme variations in dryness and humidity of the air, checking the vigor of plants, favor the appearance and presence of the red spider quite as much as extreme and continued dryness of the air.

The aphids or plant lice are readily discernable when they appear on plants, as they are sure to do under nearly all conditions. They are small, have elongated, succulent bodies, move about slowly and awkwardly, on rather long, hairlike legs, and are most commonly of a pale green color, though often brown or reddish, and sometimes of other shades. Fumigation of the plants in a closed box with burning tobacco stems will kill them. Latterly florists evaporate a liquid extract of tobacco (which is sold by dealers in florists' supplies) by dropping a hot iron into a pan of it. A tea made by soaking tobacco stems in water for a few hours, and applied with a syringe, is effective, and a safe remedy in inexperienced hands. A tablespoonful of tobacco sheep-dip, or extract of tobacco, to a couple of gallons of water, also makes an effective syringing or dipping solution. As mentioned above, we should use care, especially in the winter time, when the soil often dries out slowly, to avoid soaking it when already wet or sufficiently moist.

[Illustration: One of the kind which sucks its food]

Mealy bug has a small, flat, tortoise-shaped body, from about one-sixteenth to one-eighth of an inch long. The Insects collect in masses in the axils of the leaves. They are covered with a white mealy or cottony substance, and are readily recognized, although persons unfamiliar with their appearance have sometimes mistaken them for bits of down or cotton lodged upon the foliage or in the axils of the leaves.

The young are small, and likely to escape observation unless one looks closely. They are flat, of a creamy or pinkish tint, and lie close to the surface of the leaves, especially on the under surface. Coleus and bouvardias are among the plants upon which mealy bugs are most often found. Owing to the oily nature of their covering, it is difficult to wet their bodies with any ordinary liquid that may be applied for the purpose of destroying them. Fir-tree oil is one of the most effective remedies for them. This liquid is rather expensive, but for a small collection a gallon can will last for a long time. It is also effective against other Insects. For mealy bugs, two tablespoonfuls of the oil to one pint of water will make an effective dipping or spraying solution.

Soft or rain-water should be used, and tin, wooden, or earthenware vessels. Galvanized iron vessels are to be avoided. Apply forcibly with a syringe or atomizer, preferably in the evening. If effective, the mealy bug will turn buff-color. For other Insects, except for the scale, mentioned below, the solution will not need to be more than half or a fourth so strong. Where there are only a few mealy bugs, the plant may be gone over with a soft brush and the Insects crushed.

[Illustration: The codlin-moth]

Scales are most commonly of a brown or whitish color, flat or tortoise-shaped, and easily seen. They adhere closely by the under surface of their bodies to the stems, branches, and foliage of woody plants. The mature Insect is stationary, and its body at length becomes a shell containing hundreds of eggs. These hatch, and the young emerge from the shell, crawl about and settle, to develop into the familiar form. A strong solution of fir-tree oil, like that used for mealy bugs, is a good remedy. A strong solution of whale-oil soap, made by adding an ounce or more of the soap to three gallons of water, even more if necessary, is also useful in combating them. After dipping or syringing the plants they may be allowed to stand over night, when they should be rinsed off with clear water. Applications may need repeating every three or four days until the Insects are gotten rid of. It is difficult, for a time, to tell when they are dead. If killed, the bodies will fall off easily, and in the case of the soft-shelled species shrivel up somewhat after a time. Kerosene and water emulsion (see _Kerosene_) will kill them.

INSECTICIDE. A substance which will kill insects. Insecticides are of two general classes--those that kill by contact (see _Kerosene_), and those that poison the insect (see _Paris Green_ and _Hellebore_).

IRIS. Many handsome perennials, of which the Blue Flag is familiar to every old-fashioned garden. Most Irises thrive best in a rather moist soil, and some of them may be colonized in the water in margins of ponds. Gardeners usually divide them into two sections--the tuberous-rooted or rhizomatous, and the bulbous. A third division--the fibrous-rooted--is sometimes made. The common and most serviceable species belong to the tuberous-rooted section. Here belongs the beautiful and varied Japanese Iris, _Iris laevigata_ (or _I. Kaempferi_), which is among the most deserving of all hardy perennials. Most of these Irises need no special care. They are propagated by division of the rootstocks. Plant the pieces 1 foot apart if a mass effect is desired.

When the plants begin to fail, dig them up, divide the roots, discard the old parts and grow a new stock, as before. _I. Susiana_, of this section, is one of the oddest of Irises, but it is not quite hardy in the North. Of the bulbous section, most species are not hardy in the North. The bulbs should be taken up and replanted every two or three years. The Persian and Spanish Irises belong here. The bulbs give rise to but a single stem.

KALE. A low-growing, spreading plant belonging to the cabbage family and extensively used for winter and spring greens. The same culture as given to late cabbage is suitable. At the approach of severe freezing weather a slight protection is given in the North. The leaves remain green through the winter and may be gathered from under the snow at a time when material for greens is scarce. Some of the Kales are very ornamental because of their blue and purple curled foliage. The Scotch Curled is the most popular variety. Kales are extensively grown at Norfolk, Va., and southward, and shipped north in winter. Let the plants stand 18 to 30 inches apart. Young cabbage plants are sometimes used as Kale. See _Collards_. Borecole is a kind of Kale. Sea Kale is a wholly different vegetable (which see).

KEROSENE is fatal to insects. It is likely to injure plants if applied full strength, although if applied in full sunlight (so that evaporation takes place rapidly) it may do no harm. It is safest to apply it in dilution. Of late, there are pumps which mix or emulsify Kerosene and water in definite proportions, and this mixture (in the proportion of ? or Kerosene) is fatal to insects and usually harmless to plants.

The standard Kerosene emulsion is with soap, but the perfection of mechanical devices for emulsifying it with water is probably destined to supplant the soap emulsion.

_Kerosene Emulsion._--Hard soap, pound; boiling soft water, 1 gallon; Kerosene, 2 gallons. Dissolve the soap in the water, add the Kerosene, and churn with a pump for 5 to 10 minutes. Dilute 10 to 25 times before applying. Use strong emulsion, diluted four times in winter, for all scale insects. For insects which suck, as plant-lice, mealy bugs, red spider, thrips, bark-lice or scale. Cabbage-worms, currant-worms, and all insects which have soft bodies can also be successfully treated.

KOHLRABI. This vegetable looks like a leafy turnip growing above ground.