ELECTRIC PROPAGATOR

Evening Star, Issue 21689, 7 April 1934, Page 23

ELECTRIC PROPAGATOR

Although there are several electric heaters on the market for heating cold frames, the need of the amateur with a cold greenhouse—namely, an electric propagator with sufficient capacity to supply his needs at reasonable figure, both in running costs and initial outlay, is still far from beiug a practical possibility (writes a contributor to ‘Popular Gardening,’ London). I have experimented with this kind of propagator lor a number of years, and evolved a type which has been in use for the last two seasons. It costs only five shillings to make, and provides ample space. It will give a maximum temperature rise of ladeg Fahrenheit, and a minimum of Bdeg Fahrenheit from the external temperature, with a consumption of 80 watts (five units per week). This costs 2Jd per week at Jd per unit. The two main points which had to be considered were ventilation and hardening off the plants. The sides are made of 6in toilgued and grooved floor boarding, the tongue at the top, and corner posts are made from IJiii square battens, with one corner of each batten radiused off. These posts project lin below the sides, leaving a lin gap all round.

The hinged top is built up from 1 iin by lin battens and thin laths, and supports - a glass pane. The laths fit over the tongue on the. sides, thus forming a double bntfle, to prevent air escaping front the topi This, at tifst sight, looks as though ventilation will be hampered, but this is explained below. The heating arrangement consists of two 200-volt carbon filament bulbs, such as were used twenty years ago, each consuming about flO watts, and costing a few pence. These are arranged in series sp that each bulb receives only half the supply' voltage, when tlie total power consumption will be found to be approximately 80 watts.

These bulbs only glow an change colour, so that less than i per cent. ofL the energy goes in light, while tile remainder is spent in heat. The life of the-bulbs is practically- indefinite with ordinary treatment, and the top half should be ■ covered with tinfoil, glued oh, to stop radiation through the top of the propagator. The bulbs are held hy ordinary’ bayonet holders, carried by . a piece of zinc screwed to the side of the propagator. Ventilation is automatic. Cold, dry air is drawn from the space below the bulbs, heated and circulated round the top of the pots. As the pots contain damp soil, the air becomes damp and falls, passing out of the air gap below the sides, more hot air taking its place. Practice has been found to substantiate this theory, for I have not had a single case of damping off. The seeds or cuttings are first started in close proximity to the bulbs, and gradually moved outwards to the farthest point before placing them in the cold greennouse, other pots taking their place next to the heating felfement. Staging may be made to bring 3in pots nearer the glass if required, although converted seed boxes provide excellent improvised staging. Thfe advantages of electricity over oil for this purpose are that it is clean, needs no attention, and there are no fumes.

The propagator is portable, and after it lias done its work may be lifted from the staging to make way for the usual plants during summer. The whole structure should be give!) two or three coats of good paint before being used.