Roy's Propagation Tips

A Greenhouse provides gardening pleasure all year-round, raising seedlings, rooting cuttings, caring for houseplants and extending the season for growing fruit and vegetables. When conditions are unfavourable outdoors, you can escape into  the artificial climate of the greenhouse and get on with some timely propagation or repotting houseplants, etc., of course, always making sure you have adequate cups of tea,  it can be thirsty work.

The protected environment enables you to sow seed early, bringing on half hardy plants ready for outdoor planting when the weather is right. However, greenhouses require adequate ventilation at all times of the year, to prevent problems with fungal diseases.

Tomatoes, cucumbers, melons and strawberries can be started off earlier than would be possible outside for an early harvest and extended cropping period.

Raising plants from seed saves money and is easy. A wider variety of seeds are available from seed catalogues with many, not available in the shops. Seed catalogues are also an excellent form of information. Alternatively, save your own seed in a cool dry place. You should note, F1 hybrids will not come true from saved seed. If you are not too fussy about the varieties, you can save a fortune by collecting the free packets of seeds from your favourite garden magazines, which are in abundance late winter, early spring.

Given the right conditions, most seeds are straightforward and will grow quickly after sowing. Most require a temperature of 20-30C (68-86F) for successful germination. An electric propagator will maintain the required temperature thereby improving germination. For a larger area, soil warming cables with a thermostat can provide a cost effective alternative.

Check dates on the packet, don't waste your time using old seed, particularly if the packet has been opened as seeds quickly loose their viability once exposed to the atmosphere. You should always follow the instructions on the packet and note that seeds germinated early, will need sufficient warmth to keep them growing.

You will need good quality seed-sowing compost and you may prefer to follow Geoff Hamilton’s example and avoid peat based composts. My experience is that the more open, "warmer" composts such as peat or coir give better results with most seeds, than the traditional John Innes which is excellent for potting and growing on.

Fill the pots with compost and level off the surface, gently firming down so that the compost is roughly 1/2" below the side of the pot. I find the bottom of a similar pot or tray works well for this or if you sow a lot of seeds make yourself a tool from a shaped piece of plywood with an appropriate handle.

For fine seed, water the compost with a fine rose before sowing or allow to stand in a shallow tray of water until thoroughly moist, but not saturated. Larger seed can be watered after sowing.

Sow seed evenly and THINLY over the surface, large seeds can be sown individually into the compost.

Most seeds need covering, use a thin layer of compost, Vermiculite or Perlite to the depth indicated.

Not forgetting to label, cover with polythene, or newspaper and a single pane of glass. Protect from strong, direct sunlight, but keep the compost moist.

Check for signs of growth daily. At the first signs of germination, remove the covers, Always protect young seedlings from direct sunlight for the first few days.

Large seeds can be sown directly into cell trays, divided into small, individual compartments which need no pricking out. In my opinion these are well worth the extra cost, to save this labour of love at such a busy time of year, particularly if the trays can be reused for economy.

To avoid 'damping off,' hygiene is essential. Composts must be sterilised and pots should either be new or previously scrubbed clean.

As costs come down and the range available expands more gardeners are buying plugs of pre-germinated seeds to cut the early stages of propagation. However, the disadvantage of plugs is the still limited varieties available and if you want something different or unusual, seed or a combination of seed and plugs, is still the best method.

Pricking out

As soon as your new seedlings have grown big enough to handle, they are ready for pricking out.

Fill appropriate seed trays or small pots with good quality potting compost. Level and firm gently and make evenly spaced holes, I use a "dibalot" which is the size of a half seed tray and neatly makes all the holes at once saving a lot of time.

Using an old pencil (or treat yourself to a small dibber costing only a few pence) carefully tease seedlings out of their compost. Always handle them by their seed leaf - never by their main stems. Plant them carefully into the holes, trying not to disturb the root if possible.

Firm the compost around each plant, but do not tamp it down too hard. Seedlings should be planted no deeper than they were growing originally. Using a fine rose, water carefully, making sure the water is at room temperature. Again, for the first day or two, protect the young seedlings from strong sunlight.

As the young plants outgrow their space in a seed tray, they may be planted out, or transferred to a larger pot.

First, half fill your pot with compost. Teasing out the young plant, holding it gently in position in the centre of the pot. Add more compost, then firm in very gently. Make sure, the plant is at the same depth in its new compost as it was before. Water thoroughly.

Space is likely to be at a premium at this time of year. A tiny pot of seedlings pricked out, will fill two or three seed trays, so try not to grow more of each variety than you need. Excess seedlings can always be exchanged with fellow gardeners for other varieties or better still plan ahead together and each sow certain varieties and share the results.

Planting Out

Always ensure plants are fully "hardened off" before planting out. If you have a cold frame gradually transfer plants from the greenhouse to the frame. Open up the covers during the day and close to protect the plants at night.

This way the plants will gradually acclimatise to the cooler conditions outside the greenhouse. Do not plant out until all danger of frost has passed in your area. My uncle (the nurseryman) always refused to sell bedding plants until all danger of frost had passed. He used to say that half his business, came from the garden centre buyers who planted out too early and came to him for replacements when their plants were killed off by the "unexpected" frost.

There is nothing so satisfying, than sitting on the garden bench, with your favourite drink, knowing that what you see planted in your garden, you have grown yourself, entirely from seed.