SIMPLEST form of garden frame is a wooden box without a lid, a sheet of glass covering the top. This is useful for raising seedlings, striking cuttings, and for covering a plant that needs winter protection. Owing to its small size its uses are limited. For ordinary purposes, involving the use of more ground space, the orthodox frame is to be recommended. This consists of a stout wooden construction with one or more movable lights (a light being the glass and its framework, ).
As the object of a frame is to afford protection against inclement weather and to trap the warmth of the sun, it should be of stout construction, completely waterproof and free from draughts. Also, the light (or lights) should slope down to the front so that rainwater readily runs from the glass.
The best site for a frame is one sheltered by wall or fence from the north wind, the frame being backed against the shelter, with the glass sloping to the south. If the available space is limited, the frame may have to be so close to the wall or fence that it is not possible for the light to be pushed right back when the contents of the frame need attention. That difficulty may be overcome by joining the underside of the light to the back of the frame by a pair of stout butt hinges. To get at the interior of the frame the light is raised and hooked back to the wall or fence: the hook and chain being sufficiently strong to prevent any possibility of accident.
It is, of course, more convenient when the light slides back; and for general purposes two single-light frames are more valuable than a two-light frame. Seedlings and cuttings need to be hardened-off from the close atmosphere of the frame to open-air conditions, and the transition must be gradual. With two single-light frames the hardening-off process will be easy. The young plants are transferred from the frame in which they received very little ventilation to the second frame where air can be given in increasing amounts, while backward plants not yet ready for hardening-off remain for a further period in the first frame. The space made available in the first frame may then be used to raise more seedlings or to strike more cuttings. A spare glazed window sash of the right kind makes a very useful light. It is not so useful if it consists of a number of small panes with wooden bars running across; these impede the escape of rain, as does the lower part of the window sash. Without transverse bars, a window sash comes nearer to requirements, its only drawback being the bottom part of the frame- work. But this disadvantage may be overcome, to some extent, if the sash is placed on the frame so that its ‘weather’ face points upwards. It is waste of time trying to adapt to this purpose a window sash that has outlived its best days. There must be no looseness at the joints, or it will twist when handled and the glass will be broken; although something may be done to strengthen the sash by screwing metal angle-pieces at the corners. There must be no suspicion of decay in the woodwork, for the light must withstand rain from without and the action of moist atmosphere within.
As the sizes of window sashes vary, it is important when selecting the sashes that the garden frame should be constructed to match the dimensions of the sash. If a new light is to be constructed a useful size is 4ft. Long by 3ft. Wide, overall measurement, made of sound deal 3 in. wide and iin. Thick, with the corners mortised and each secured with a dowel. See also Figs. 1 and 2.
Rebates to carry the glass (and putty) are contrived by screwing to the sides and top end of the new light, strips of wood a1 in. wide by½ in. thick. The bottom end has no rebate, the glass resting flush (or almost flush) upon it so that there is no obstacle to the escape of rainwater.
A length of ordinary sash bar divides the light down the centre, the ends being cut to fit the top and bottom rails, where they are secured by screws.
Ordinary window or picture-frame glass may be used satisfactorily for the glazing of the sash, but as the light will be moved frequently any jarring movement must be avoided. The panes of glass should be puttied-in, SO that they overlap: about ½ in. of the bottom end of an upper pane projecting over the next lower pane. This is to prevent any possibility of rain dripping through, for plants hate drip. And though a moist atmosphere in the frame may be desirable in summer, to accelerate growth, the atmosphere must be dry in winter. Moist interior conditions in summer are induced by syringing.
To retain the panes of glass in position against the slope of the frame and to increase the holding power of the putty, insert brads in the sides of the light at the bottom of each pane, so that these latter are supported before the top putty is pressed on. A light should consist of as few pieces of glass as possible, consistent with safety, because grime is apt to collect at the overlap, thus obscuring daylight.
When the frame light has been glazed, the woodwork should be given two coats of paint; white is generally used, well worked in on both sides. A light of the dimensions given will fit a frame 3$ffc long by 3ft. Wide; it can be lain. Deep at the front, and i8in. Deep at the back. The difference between length of frame and length of light allows of overhang of the latter at back and front, a further safeguard against entry of water. Some advocate the gouging out of a½ in. deep channel or groove from side to side of the underside of the bottom end of the light, so that water shall not seep back into the frame. Rut if there is sufficient overhang, and a forward slope (of the angle indicated), the groove will not be essential. Seasoned timber 6in. Wide, not less than 1 in. thick, and preferably tongued and grooved, is used in constructing the frame. Corner uprights, 2 in. square, are cut to length as shown; and to each pair (a short and a long upright) the sides are screwed or nailed; then the front and the back are similarly attached. Across the centre of each side is then screwed a batten 3 in. wide, 1 in. thick, the tops of these, and the tops of the corner pieces, being sawn flush with the top edge of the framework.
To both sides, guides for the sliding light are screwed strips 3in. Wide, 1 in. thick. These are to project so that their top edges fall level with the top faces of the light when this is in the closed position. Without these guides the light is apt to slide to left or right when being moved. Construction completed, the frame is given two coats of paint (green is the generally accepted colour) inside and out, working well into the corners. Fumes of the paint must be given time to dissipate before the frame is put to use.
To safeguard the lower part of the timber from decay through contact with the soil, the frame may be placed on a permanent border of bricks or flat tiles, lodged end-to-end. Either encroaches very little on the area of soil within the frame, and their provision should add years to the serviceability of the frame. There should be no spaces or cracks between the members of this slight foundation for wind to penetrate. Naturally, the site will be levelled before laying down the tiles or bricks, and the soil on which they are to rest will be made quite firm. With bricks, it is advisable to sink them half their depth, to prevent shifting.
Construction of a two-light frame is on similar lines, the width being increased to 6ft. With the addition of a centre-piece running from back to front. This centre-piece divides and supports the inner edges of the two lights. It is made of two pieces of in. or 1 in. timber, as, screwed together. The lower piece is sunk in the frame at back and front, its top edge flush with the frame, and there screwed or nailed. A groove ½ in. wide and deep is made in the lower piece, on either side of the piece against which the lights will slide. The grooves run full length, their purpose being to carry away any rainwater that may trickle in between the lights. It will be noted that the two-light frame is further strengthened by two battens, screwed to the inside at front and back the tops of these should be cut to take the ends of the central dividing piece. A three-light frame will be 9ft. By 4ft., depth remaining as before; two dividing pieces, with corresponding battens, are provided.
For easier handling of the lights when these have to be pulled back, metal handles may be screwed to the rear of each. When complete ventilation is to be given to the frame, or full access is required, the light should be pulled right back; the wind will not shift it in that position, as it is quite likely to do if the light is precariously balanced or rested on the ground at a sharp angle.
For propping up the light a few inches, a block of wood or an inverted flower pot is placed between the front edge of the light and the frame; or a stout stake will do. Whichever is used, the support should be given to both sides of the light; otherwise strain is thrown on the side without support and the frame of the light may become distorted.
Pieces of putty which may fall away or become loose should be renewed, and an annual repainting, particularly of the wood parts adjacent to the ground, will postpone the day when signs of decay become evident in the woodwork. Cracked panes of glass must be changed before the broken pieces drop on the seedlings, and to keep the frame weather-tight. Clean the glass -panes at regular intervals.