All plants have a relative degree of susceptibility to frost which constitutes an important guide to starting them. Tender plants are those that are checked or stunted by an approach to frost and are injured by even the slightest frost. Usually they are natives of warm countries, and if they are perennials or biennials their roots must be dug up and brought indoors for the winter. These indoor hibernators include herbaceous perennials such as begonias, fleshy rooted plants such as cannas and dahlias, and shrubs such as lantanas and geraniums.
Annual plants which may be sown after freezing weather and which will stand frosts are hardy annuals. They should be planted as soon as the ground is sufficiently dry to work. The very hardy may be sown before the passage of freezing weather-in ground that may freeze by night but thaws by day.
Hardy perennials are those whose roots will survive an outdoor winter even though their tops will die to the ground each year.
Half-hardy plants may be sown in open ground a week or two before the expected date of the last frost or started under glass and transplanted to open ground while there is still a possibility of light frost. They do better in temperatures above the frost point, however.
Many tender plants must be started under glass, especially in northern latitudes, in order to have a long enough season in which to develop, for most of these natives of tropical and subtropical climates require a long growing season.
Frequently there is only an arbitrary distinction between the annual, biennial, and perennial. The snapdragon and the pansy are striking examples of plants that will bloom from seed in their first season, and yet the snapdragon is a perennial and the pansy a biennial. With both these flowers, however, a finer bloom results from plants newly grown each year.
Moreover, some plants that give their best results if raised each year from seed must be planted by midsummer at the latest in order to bloom the next year. If their life cycle is completed within the space of the next year and they die, they are called biennials. If they survive and grow the third season, they are perennials.
Since trees and shrubs, the woody-topped vegetation, are permanent adornments of the property and far outlast even the longestliving perennial, they are treated separately, for they are fixtures of the scene. In this chapter we deal largely with the comparatively transitory inhabitants of the garden, herbaceous plants we know as flowers.
Basic equipment for the garden
As the artist's studio needs its easels, the seamstress's room her sewing machine, the printer's shop its presses, the garden too requires certain basic equipment to function efficiently. This basic equipment should include hotbed, coldframe, pit, flats, and compost pile.
A hotbed is literally an incubator. Specifically for gardeners it is an enclosed bed of soil heated by fermenting manure. A coldframe is structurally similar to a hotbed, differing from it in that it employs no artificial means of beating. It is a device to protect plants from cold without forcing them to growth.
If the maximum of pleasure is to be obtained from a garden, it must produce a continuous pageant of flowers throughout the season. Since so many flowers will not produce an early bloom if the seed is sown in open ground, the gardener must resort to the use of coldframe or hotbed to lengthen the growing season.
As an example of the gain of growing time, in the latitude of Washington, D. C., the time for sowing seeds that require higher temperatures for germination may be advanced from May 1, the normal date for outdoor sowing, to March 1. Seeds sown in a gentle hotbed at this earlier date will advance the season of bloom by two weeks or more if the plants are handled properly.
Constructing the equipment
Gardeners who are handy with tools can make their own hotbeds, following the simple and explicit directions of the Department of Agriculture:
A temporary hotbed may be made by using fermenting stable manure from grain-fed horses, preferably that with a small quantity of straw or litter in it. The manure should be placed in a broad, flat heap and thoroughly compacted by tramping. A heap 8 or 9 feet wide and any multiple Of 3 feet in length, with the manure 14 to 16 inches deep, will give sufficient heat for the latitude of New York City and of Kansas City, Mo. Farther north, the heap should be made deeper and broader. Upon the surface of the manure heap a frame ... (should be placed affording) ample space for the development of the plants within. The backboard of this frame is usually 12 inches wide and the front 8 inches, and the two are connected by a tapered board 12 inches wide at one end, 8 inches wide at the other, and 6 feet in length. The back and front of the frame are made in multiples of 3 feet in length, with an inch added for each division space between sash, which is provided for by the use of a T-shaped piece let into the frame to stiffen it and serve as a guide for the sash. (Durable wood, such as redwood, cypress or red cedar, should be used) If severe weather is likely to occur during the time the hotbed is in use, the frame should be banked with manure to give additional beat and protection. After placing the frame upon the manure heap, about 3 inches of good garden loam should be scattered uniformly over the area enclosed by the frame. Place the sash in position immediately and allow the bed to heat up. Do not plant any seed in the bed until the temperature begins to subside, which will be in about three days after the sash are put in place. When the temperature has fallen to 85º or 90º F. planting may be safely begun.
A permanent hotbed may be so constructed as to be heated with fermenting manure or by radiating pipes from the dwelling or greenhouse beating plant (if you have a greenhouse).
For a permanent bed, in which manure is the supply of heat, a pit 2 to 2 1/2 feet in depth, according to the latitude in which the work is to be done, should be provided. The sides and ends may be supported by a lining of planks held in place by posts 4 feet apart, or, better still, a brick wall 9 inches thick . . . may be used. In either case, the pit lining should come flush with or above the surface of the soil. The site for the pit should be on naturally well-drained land, and a tile drain from the bottom of the excavation should be provided to prevent water from accumulating in the pit and stopping the fermentation of the manure during the period the hotbed is in use.
Standard hotbed sash are 3 by 6 feet in size, and the interior crosspieces for holding the sash are 1 inch wide. The pit, therefore, should be some multiple of 3 feet 1 inch in length less 1 inch, and the width should be the same as the length of the sash, 6 feet. The plank frame or brickwork of the pit may be extended above the surface of the ground sufficiently to allow for placing the sash immediately upon these permanent structures, or a frame such as is described in connection with the construction of a temporary hotbed ... may be used. In the fall the pit should be filled with leaves or straw and covered with loose boards or shutters to prevent it from becoming filled with snow and ice in the North, so that it may be ready for use early in March there, or in January or February farther south.
Now comes the most important part of the hotbed, the windowlike cover. Putting the glass into the sash which provides this cover will determine largely whether the hotbed succeeds or fails and the art of glazing might scare off the amateur carpenter from the undertaking, in which case the professional glazier takes up the chore. But for the handy gardener who wishes to do the entire job himself, the Agriculture Department's suggestions again are offered:
Hotbed sash should be constructed of white pine, cypress, or redwood, and the sash bars should run in one direction only and that lengthwise of the sash. The bars may be braced through the middle by a transverse bar placed through the long bars below the plane occupied by the glass. The two ends of the sash should be made of sound timber 3 inches wide at the top and 4 inches wide at the bottom, mortised to receive the ends of the sash bars and with a tenon at the ends to pass through the side pieces, which should be 2 1/2 inches wide.
The glass should be bedded in putty, i.e., the rabbet (groove) in the sash bar that is made to carry the glass should be filled with soft putty, and the glass, crowning side up, pressed firmly into the bed of putty and securely fastened with shoe nails or wire brads. Glazing points are not sufficiently secure. The first glass to be placed in any frame is the bottom light, i.e., the pane nearest to the front or lowest side of the hotbed when the sash is in place. The next light should be bedded in the same manner as the first and so placed as to lap about three-sixteenths of an inch over the top edge of the one first placed, like shingles on a roof. Brads should be driven below the lower corners of the second pane in order to prevent it from slipping down over the under one. The same method of procedure should be continued until the frame is filled with glass.
While a frame with two courses of glass will admit a little more light than one with three, the breakage is somewhat less with small glass and the cost of repairing correspondingly less, and for these reasons the three-course frame is more desirable. Nowadays many hotbed sash are made with a groove or slot into which. the glass may be slipped and fastened at the bottom by brads to prevent it from slipping out. Grooved sash have the commendable feature of being cheaply and quickly glazed, but as the glass cannot be lapped and as no putty is used, the sash are not watertight and do not furnish as good protection from the wind as those in which the glass is bedded in putty.
Using the hotbed
During cold northern nights extra protection, such as straw mats, strips of burlap and old carpet, or board shutters will be required. The heat from the direct rays of the sun which is generated inside a good hotbed is intense, and on bright days, even when the outer temperature is near freezing, the sash must be raised slightly to let the hot air out and save the young plants from injury.
Water the hotbed in the morning only, and only on bright days. To water a bed the sash naturally must be opened, allowing the accumulated hot air to escape; and the water itself lowers the soil temperature. Thus night watering in cold weather greatly increases the danger of frost, and the combination of dampening the leaves and confining them at night creates conditions favorable to the development of mildew and damping-off fungi.
Building and using coldframes
The simplest kind of coldframe is built similar to the temporary hotbed and is placed on sheltered, well-drained ground. Through the glass covers the sun's rays, on bright days, warm the air inside the frames, and by covering them at night with shutters or straw mats the heat of the interior is retained to bring the plants safely through rough weather. As an extra caution against cold you may bank the frames with earth.
The principal element of successful use of the coldframe is proper ventilation. Since the main use of the coldframe in the winter is to keep the plants healthy without forcing growth, and in the spring to protect them against occasional cold before the time for openground planting, the temperature must be guarded carefully lest it reach a level that spurs rapid growth.
In sunny weather lift the sash just enough to let in air which keeps the temperature low about the leaves of the plants. On some bright days, even in the heart of winter, you will have to take off the sash completely around noon to preserve a correct temperature. But be very careful in ventilating the coldframe, and watering the plants it houses, that you do not cut down the temperature inside late in the afternoon, when there is no continued sunlight to recompensate for it, or you may cause frost injury to your plants.
It can be seen that the coldframe is a highly useful and necessary adjunct to the garden. It will enable you to make many of your annuals grow perennially, or give your flowers a much longer period of bloom if they are sown in the fall and carried through the winter in a coldframe, but only the really hardy plants will endure the winter safely in such a protection.
A pit is simply a more elaborate and efficient coldframe, requiring an excavation which should be 2 or 4 feet deep and lined with plank or brick walls, as in the permanent hotbed. It provides more protection than an ordinary coldframe because it is dug into the soil, which has warmth. The pit is most useful in latitudes in which the freeze of the soil does not go more than 10 or 15 inches deep. Seedlings in trays or flats may be carried through the winter in pits as safely as in frames. Precautions in ventilating and watering the coldframe maintain for the pit as well.
Flats are among the most useful items of a garden's equipment. They are simply wooden trays, with built up sides, for sowing seeds, and may readily be made at home. If you have a few boards you can knock one together easily, or you can saw one off the top or bottom of a small wooden packing case in which your grocer or druggist has received a shipment of canned goods or soap. Cut some holes in the bottom, just large enough to permit draining but not so big that the soil piles through.
Of course coldframes, hotbeds, glazed sash, flats, and coldframe mats all can be bought, ready-made from garden supply firms.
One thing every good gardener should have at hand is a good compost pile. Compost in gardening is simply a compound for fertilizing land. It is a decayed mixture of soil and organic matter, such as manure and any available plant remains-leaves, lawn clippings, weeds, leaf mold, peat. It provides a fine, rich soil of wellrotted fertilizer available at all times for growing plants.
Do not be alarmed by the suggestion that a compost pile will create an unsightly object on your grounds. It may be stored in a wooden bin, surrounded by evergreens, and will be little noticed. A bin 6 feet square will house a compost pile ample for any average garden. Stack in manure, then leaves, cover it with sods or turf. The rains will wet it down and help it decay. Spading or turning the heap occasionally also will hasten the decay, but as a rule it is sufficient merely to pile the ingredients together.
It is wise to open vent holes through the top of the pile, simply by jamming a rake handle down into it at several places, to release possible excess heat caused by fermentation. The release of the heat through the vents prevents. possible burning of the organic substance in the process of rotting.
In taking soil from the compost pile, do not shovel it off the top but slice it from top to bottom of the heap. Keep the pile clear of grasses or weeds which have gone to seed. There is no point in helping weeds to grow. They do it on their own quite competently.