How To Use Propagating Frames

Some seedlings and cuttings need a hotter or moister atmosphere than that of the greenhouse. To obtain this a propagating box or frame is used. In its simplest form this is a box of any convenient size and about 1 ft. in depth placed over the hot water pipes or heating apparatus at the warmest end of the house and covered with panes of glass. The box is half filled with sand or granulated peat in which pots containing the seeds or cuttings are plunged. The purpose of the fibre is to retain heat and moisture. More elaborate propagators and propagating frames contain their own heating or soil warming devices.

Seed Raising under Glass. It is not necessary to employ numerous composts for raising seeds of different plants. One good mixture will serve for all. That known as the John Innes Seed Compost (JIS for short) is as follows:propagating-frame

  • 2 parts by loose bulk of medium loam.
  • 1 part by loose bulk of good peat.
  • 1 part by loose bulk of coarse silver sand.

To each bushel of this mixture add:

14 oz. of superphosphate (16% phosphoric acid). oz. of ground limestone or chalk.

Pass all ingredients through a 1/4-in. mesh sieve. It is an advantage if loam is first sterilized by steam or electricity. An alternative to loam-based compost is peat-based or all-peat compost of which various brands are available.

Seeds may be sown in earthenware or plastic pans 2-3 in. deep and of any diameter, pots, usually 4 or 5 in. diameter, and in wooden boxes or plastic trays 11-2 in. deep. All must be well supplied with drainage holes or slits, and these must be covered with crocks (broken pots), and small rubble or sphagnum moss. Make soil firm (except for pure peat compost) but do not fill within 1 in. of the rim. Smooth surface with a planed block of wood and scatter seeds evenly. Cover with a sprinkling of finely sifted compost. A good guide is to cover seeds with twice their own depth of soil; very fine seeds,

such as those of begonia and gloxinia, are not covered at all, simply pressed into the surface. Cover seed pans with panes of glass and sheets of paper. Directly seedlings appear, remove paper. A day later tilt the glasses on pebbles or wooden tallies, and a day or so after that remove altogether. Most seeds will germinate more rapidly if placed in a propagating frame, but excessive temperatures are detrimental for some seedlings and may cause damping off. Seeds of most popular greenhouse plants germinate well in a temperature of from 60-70F.

Soil in which seeds are to be sown should be moist but not wet. It must not be allowed to become dry while seeds are germinating. Further water may be required and should be given by semi-immersion.

Pricking Off. Almost all seedlings must be pricked off, i.e. transplanted to other receptacles, as soon as they can be handled conveniently. Exceptions are mainly for bulbous-rooted plants, which may be sown extra thinly and allowed to grow on undisturbed for the first year.

Prick off into compost and receptacles similar to those used for sowing. Seedlings are lifted carefully with a sharpened stick, singled out (except with certain annuals) and dropped into dibber holes about 2 in. apart each way. A dibber the thickness of a stout lead pencil is used. Make soil firm round roots (but not for pure peat composts) and, finally, water freely through a fine rose. Seedlings should be shaded and given reduced ventilation for a few days until established. Subsequently, most kinds may be stood on staging or a shelf near the glass.

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