Part 11

The smaller the glass-house the more difficult it is to manage, because it is likely to be more variable in temperature, moisture and other conditions. This is particularly true if the house is a small lean-to against the south side of a dwelling house, for it becomes very hot at midday and comparatively cold at night. In order to moderate the heat in these little houses, it is ordinarily advisable to use ground glass for the roof or to whitewash it. The house conservatory may be heated by a coal stove, but the best results are rarely to be attained in this case. A stove is likely to leak gas, and the temperature is more or less uneven. The best results are to be attained when the conservatory is heated by steam or hot water, piped in the modern fashion with wrought iron pipes, which go together with threads. If the conservatory is heated from the heater which supplies the dwelling house, it should have an extra amount of pipe; otherwise it will be necessary to keep the dwelling house too hot for comfort in order to maintain the conservatory at its proper temperature. It is always best, when practicable, to heat the conservatory with a separate apparatus. There are various small hot water and steam heaters, the size of coal stoves, which are excellent for the purpose. For a small conservatory, hot water is usually preferable to steam, since it is less likely to fluctuate. For large establishments, however, the steam is usually the better. For further discussions of related subjects, see _Hotbed_, _Window Garden_, _Potting_ and _Watering_.

GREVILLEA. A very graceful greenhouse plant, suitable for house culture. The plants grow freely from seed, and until they become too large are as decorative as ferns. Grevilleas are really trees, and are valuable in greenhouses and rooms only in their young state. They withstand much abuse. They are now very popular as jardiniere subjects. Seeds sown in spring will give handsome plants by the next winter.

GYPSOPHILA. BABY'S BREATH. _Gypsophila muralis_ is one of the dainty little plants called Baby's Breath. It is a low-growing annual forming compact mounds of green, thickly covered with little pink flowers. It is one of the most attractive border plants in cultivation. It is also a charming pot-plant. _G. paniculata_ is a hardy perennial having panicles of bluish white flowers. This is very graceful, and the flowers are fine for cutting and for use with sweet pea bouquets or with other choice flowers. The panicles are so lasting that they may be used in winter bouquets. The annuals may be planted 1 foot apart; the perennials 3 feet. Both are readily grown from seed, and bloom the first year.

HARDY. A relative term, used to denote a plant which endures the climate (particularly the winter climate) of a given place. Half-hardy plants are those which withstand some frost or uncongenial conditions, but will not endure the severity of the climate. Tender plants are those which are injured by light frosts.

HEDGES. Hedges are much less used in this country than in Europe, and for several reasons. Our climate is dry, and most Hedges do not thrive so well here as there; labor is high-priced, and the trimming is therefore likely to be neglected; our farms are so large that much fencing is required; timber and wire are cheaper than live Hedges. However, they are used with good effects about the home grounds. In order to secure a good Hedge, it is necessary to have a thoroughly well-prepared, deep soil, to set the plants close, and to shear them at least twice every year. For evergreen Hedges the most serviceable plant in general is the arborvitae. The plants may be set at distances of 1 to 2-1/2 feet apart. For choice Hedges about the grounds, particularly outside the northern states, some of the retinosporas are very useful. One of the most satisfactory of all coniferous plants for Hedges is the common hemlock, which stands shearing well and makes a very soft and pleasing mass. The plants may be set from 1 to 3 feet apart. Other plants which hold their leaves and are good for Hedges are the common box and the privets. Box Hedges are the best for very low borders about walks and flower beds. The dwarf variety can be kept down to a height of 6 inches to a foot for any number of years. The larger-growing varieties make excellent Hedges 3, 4 and 5 feet high. The ordinary privet or prim holds its leaves well into winter in the North. The so-called Californian privet holds its leaves rather longer and stands better along the seashore. In the southern states, nothing is better than _Citrus trifoliata_.

For Hedges of deciduous plants, the most common species are the buckthorn, the European thorn apple or crataegus, osage orange, and various kinds of roses.

Hedges should be trimmed the year after they are set, although they should not be trimmed very closely until they reach the desired or permanent height. Thereafter they should be sheared into the desired form in spring or fall. If the plants are allowed to grow for a year or two without trimming, they lose their lower leaves and become open and straggly. Osage orange and some other plants are plashed--that is, the plants are set at an angle rather than perpendicularly, and they are wired together in such a way that they make an impenetrable barrier just above the surface of the ground.

HELIANTHUS. See _Sunflower_.

HELICHRYSUM. These are perhaps the most popular of the Everlastings (which see), having large flowers of several colors. They grow readily from seed, blooming from July to October. Height 10 inches to 2 feet. Should be planted or thinned to stand 18 inches apart.

HELIOTROPE. A universal favorite house or border plant, growing readily from cuttings or seeds, and producing quantities of fragrant violet, purple or white flowers. One of the best methods of cultivation is to set a strong plant in the border and peg the new growths to the ground, where they will root and form a perfect mat, flowering profusely during the fall months until frost. They will endure the temperature of a living room well if the room is not too dry. Red spider is a natural enemy of the Heliotrope, and when once it obtains a foothold is a very difficult pest to manage, but frequent syringing with water will keep it in check. A light, rich soil and an abundance of heat are their requirements. Height 1 to 3 feet. Propagated by cuttings or layers.

HELLEBORE (White Hellebore) is often used for the killing of currant-worms and other insects (see _Currant_). It is not so poisonous as the arsenites, and therefore is to be preferred when it is necessary to apply a poison to nearly ripe fruit. It is usually applied in a spray with water, at the rate of 1/3 ounce to the gallon. It is harmless to foliage.

HELLEBORUS, or CHRISTMAS ROSE, may be had in flower at the holidays if grown in a frame and protected. The usual time for it to flower in the open border is in March or early April. It will continue to bloom for many years if grown in a shady place. Roots may be divided as an increase is wanted. It may also be grown from seeds; and seedlings may be expected to bloom a year from the spring in which they are sown. Height 6 to 10 inches.

HEMEROCALLIS, or YELLOW DAY LILY. The advice given under Funkia will apply to this.

HERBS are plants which die to the ground in winter. They may be annual, biennial, or perennial. For a list of annual Herbs suitable for the flower garden, see the articles on _Annuals_ and _Bedding_. A border or free mass of perennial Herbs is one of the charms of any place. It is informal, easy of care, and self-sustaining. The large part of the mass should be composed of common and hardy things--wild or from gardens--and incidental features may be made of the choicer and rarer exotics. In most cases, plants look better when judiciously mixed than when planted one kind in a bed. See _Border_.

HIBISCUS. Annuals and perennials, some of them shrubs, with showy, hollyhock-like flowers. The annual Hibiscuses are very satisfactory. They grow quickly and flower freely. The flowers are usually white or yellow, of large size, and appear from July on. The herbaceous perennial kinds are amongst the best of hardy border plants, blooming in late summer and fall. The commonest of these is _Hibiscus Moscheutos_. Give rich, moist soil.

The greenhouse species are old favorites. They may be used in outdoor bedding through the summer, lifted in the fall and cut back. Keep rather dry and dormant during winter. Propagated by cuttings.

HIPPEASTRUM. Consult _Amaryllis_.

HOES should be of several patterns if the most efficient work is to be done in the garden. The ordinary Hoe is adapted only to the rougher and coarser Hoe-work, such as digging and fitting the ground. For much of the subsequent tillage, some of the narrow-blade and pointed Hoes are excellent. For cutting off weeds, the push Hoe or scarifier is excellent.

HOLLYHOCK. These old garden favorites have been neglected of late years, primarily because the Hollyhock rust has been so prevalent, destroying the plants or making the unsightly. The double varieties seem to suffer the most; and for that reason, and from the fact that the less formal type is in favor, the single varieties are now the most generally grown. Their culture is very simple. The seed is usually sown in July or August, and the plants set where wanted the following spring. They will bloom the same year in which they are transplanted--the year following the seed-sowing. New plants should be set every two years, as the old crowns are apt to rot or die after the first flowering. For rust, spray early with Bordeaux mixture or ammoniacal carbonate of copper.

HOP, ORNAMENTAL. _Humulus Japonicus_, or the annual HOP, is one of the best rapid-growing screen vines in cultivation. It makes a dense canopy of attractive foliage. The leaves are finely cut, and in one variety variegated with white. This variegated variety is a fine vine for a porch or front screen, always attracting attention to its markings. This Hop is propagated by seed sown in boxes in March. When once established, it will seed itself and start as soon as the soil becomes warm. Set plants 4 to 8 feet apart. Height 8 to 20 feet.

HORSERADISH. As a kitchen garden vegetable, this is usually planted in some out-of-the-way spot and a piece of the root dug as often as needed, the fragments of roots being left in the soil to grow for further use. This method results in having nothing but tough, stringy roots, very unlike the product of a properly planted and well cared for bed. The best roots are those planted in the spring at the time of setting early cabbage, and dug as late the same fall as the weather will permit. It becomes, therefore, an annual crop. The roots for planting are small pieces, from 4 to 6 inches long, obtained when trimming the roots dug in the fall. These pieces may be packed in sand and stored until wanted the following spring. In planting, the roots should be set with the upper end 3 inches below the surface of the ground, using a dibber or sharp-pointed stick in making the holes. The crop may be planted between rows of early-sown beets, lettuce or other crop, and given full possession of the ground when these crops are harvested. Where the ground is inclined to be stiff or the subsoil is near the surface, the roots may be set in a slanting position. In fact, many gardeners practice this method of planting, thinking that the roots make a better growth and are more uniform in size.

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.

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 deg. the seeds of tomatoes and egg-plants may be sown; and when it begins to fall below 80 deg., 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_.

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_.

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.