Propagation Tools and equipment FAQs

I would like to propagate from cuttings a few plants on my window sill, but do not want to go to the expense of a propagating unit. Can I get round this?

The main problem you need to solve is that nearly all cuttings need a humid atmosphere: in dry air their leaves soon shrivel and die because there is as yet no root system to replace the moisture lost through rapid evaporation. Place four canes in the pot of cuttings and drape a polythene bag over them, securing it to the pot with a rubber band. Place the pot in a bright spot, but out of direct sunlight, in a room where a temperature of about 18°C (65°F) is maintained. Rooting will take a few weeks: its occurrence will be indicated by new growth, so the cuttings should not be disturbed until this is visible.

I will need a heated propagator to start off my seedlings during the winter months. Proprietary models seem to be very expensive, so I wondered if it would be feasible to make my own. Could you tell me what materials I would require?

First you will need to make a box about 150 mm (6 in) deep. Line the base with approximately 50 mm (2 in) of sand. Lay on the sand an electric soil-warming cable (which needs to be thermostatically controlled) in loops about 75 mm (3 in) apart across the full length of the bottom of the box. Cover this with a further 50 mm (2 in) of sand. Complete your propagator by making a close-fitting plastic or glass lid to help maintain a warm, humid atmosphere. Alternatively, for a slightly greater outlay, you could buy a proprietary heating panel. Most types made for the amateur gardener will fit under a standard plastic seed tray, which is equipped with a clear-plastic cover.

I’m a keen gardener and would like to start propagating my own plants, especially from cuttings. Could you please advise me on the best sort of propagating knife to buy? There are many different types available.

It is important to choose a knife with a good-quality steel blade which can be sharpened to a keen edge. Poor quality steel (or that which is highly chromed) will soon become blunt and will wear down quickly when sharpened. For general propagation choose a medium-weight knife which opens easily and is comfortable to use. Go for one with a straight blade which is set well back into the handle, so that it will not become loose with wear. (Knives with a curved blade are best avoided as they are difficult both to use and to sharpen). If you buy a knife with a blade which is honed only on one side of the edge, check that it suits you, for it is either left- or right-handed. Keep your good knife for propagation only; use a cheap pen knife for cutting string.

My propagating knife needs sharpening quite often, and I have not yet been able to master this task. I have a carborundum stone, but all I seem to do is wear down the blade. Could you explain how I should use it?

Slightly moisten the carborundum stone with a little clean mineral oil and gently push the whole blade along the full length of the stone. If it is a two-sided blade, hold it at a very shallow angle and push it in a forward direction only. Do this several times, then repeat the operation on the other side of the blade. If it is a flat-ground blade, with only one sharp edge, lay it horizontally on the stone, exerting slight pressure towards the sharpened edge, and push it gently in a forward direction as before.

Is it all right to use garden soil for sowing seeds in pots? Plants I grow outside seem to germinate well.

Your garden soil will grow outdoor plants; but it is unsatisfactory if used in pots. This is mainly because it is not sterile and can harbour pests and diseases which will compete directly with the plants being grown. Neither will it contain all the essential nutrients at the right strength for pot-grown plants. Even light soils can drain badly in pots. Instead, use one of the proprietary seed composts. These are specially formulated for containers, are essentially pest and disease free, and include all the foodstuffs necessary to grow good plants from seed.

As an economy measure, can I use yoghurt cartons instead of clay or plastic pots?

Clean yoghurt cartons and the like make excellent pots. Remember, though, to pierce plenty of holes in the base of the cartons to allow for drainage.

I have read that mist propagation guarantees better results. What is it and can it be done in a small greenhouse?

Mist propagation is a system which keeps the plant material moist throughout the rooting period. Proprietary kits, which are widely available, consist essentially of a water-supply stand-pipe surmounted by a nozzle and an automatic on/off switch that is triggered by the humidity level within the propagator. When the switch is on, the nozzle emits a fine spray. Mist propagation creates a humid atmosphere that allows maximum light to reach the cuttings; combined with the extra warmth provided by the propagator’s heating unit, it creates an ideal environment for the young plants to root in. The propagators in which the mist units are installed are available in various sizes, most of which are compact enough to be used in a small greenhouse. If you are thinking of buying a mist unit, however, bear in mind that you will need to have both electricity and water supplies to the greenhouse.

I would like to use artificial lighting in my greenhouse to supplement poor daylight in winter. What type of lamps should I use?

Fluorescent tubes specially made for indoor gardening are available; these give out light in the red to blue wave-lengths that plants enjoy. If you prefer to use ordinary tubes, choose those described as ‘cool white’. For each 300 x 300 mm (12 x 12 in) of growing area allow 15-20 watts of light, and set the tubes 300-450 mm (12-18 in) above the plants.

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