Home Gardener's Propagation (UK Only). David Squire
Seed-trays (flats) and pots
Plastic seed-trays (flats) are essential when you sow half-hardy annual seeds in greenhouses. You will also need pots in a range of sizes – ones 7.5–8 cm (3–3½ in) in diameter are most often used, and both plastic and clay types are available. When seeds are sown in pots, shallow ones, such as Jiffy pots, are useful.
Seed-tray (flat)
Seed-tray with ‘cells’
Peat pot
Jiffy pots
Sieves
You will need a flat-based horticultural sieve, 15–20 cm (6–8 in) wide and 7.5–10 cm (3–4 in) deep, to evenly cover seeds with compost. Alternatively, use a culinary sieve.
Sieve
Dibber (dibble)
Small plastic dibbers (dibbles), 10–15 cm (4–6 in) long, are useful for transferring seedlings from where they germinated into wider spacings in seed-trays (flats) or into individual pots. Plastic types are easier to keep clean than wooden ones.
Dibber (dibble)
Greenhouses
Heated greenhouses are essential for raising half-hardy annuals (summer-flowering bedding plants) in spring. Several forms are available, including ‘even-span’, ‘lean-to’ and ‘miniature lean-to’, as well as partly glazed sheds. With all of them, good ventilation is essential, as well as adding warmth in late winter and spring. Remember that the larger the greenhouse is, the easier it will be to achieve a uniform and even temperature (but it will also be more expensive to heat).
Even-span: orientate the ridge east to west
Lean-to: position against a warm, sheltered wall
Mini-type: secure to a wall that is sheltered from wind
Glazed shed: orientate the glass towards the sun
Insulating greenhouses
To reduce heating costs in late winter and spring, when sowing seeds, attach plastic bubble-wrap glazing to the inside of metal or wood greenhouses. Leave space for the ventilator to open and close, and use drawing pins to hold the bubble glazing in place in wooden greenhouses, or special plastic fittings for use in aluminium greenhouses.
Heating a greenhouse
Paraffin (kerosene) heaters: These create warmth and give off moisture that will need to escape through ventilators. They are efficient, but if badly maintained and with a wick that is set too high will produce smoke.
Electric fan heaters: Most have built-in thermostats to ensure that the desired temperature is maintained. Waterproof cables and sockets are essential; avoid hot draughts on plants.
Tubular electric heaters: These are controlled by a thermostat. Ensure that the hot air can rise freely.
Electric fan heater
Propagators
Propagators enable seeds to germinate and cuttings to develop roots without heating the entire greenhouse.
Electric propagator: Clean and efficient, but ensure that it has been safely installed for use in a damp environment.
Unheated propagator with air vents at top
Garden frame
Cold frames are ideal for acclimatizing (‘hardening off’) young plants before you plant them in a garden in late spring or early summer. They are unheated and need to be ventilated during warm weather.
Glass jars
Bell jars are traditionally made of glass and put over newly sown seeds and young seedlings to encourage germination and early growth. You can also use glass jam-jars or plastic bottles with their tops cut off.
Bell jar
Plastic bags
When taking softwood cuttings (see pages 20–21), insert short pieces of split canes into the compost and draw a plastic bag over them; secure the bag around the pot with an elastic band.
Border soil
A sheltered corner with friable, well-drained soil creates an ideal nursery bed for plants. It can also be used for hardwood cuttings (see page 22).
Mist propagation units
Professional gardeners have used mist propagation units for many generations to encourage softwood cuttings to develop roots quickly. Small, amateur units are now available. You insert the cuttings in well-drained compost (slightly heated) and the unit regularly covers the leaves with a thin film of water. This keeps the leaves cool and full of moisture until roots develop. The cuttings should then be transferred to small pots.
Always have electrical equipment installed by an experienced and competent electrician.
TIMING
Choosing the right time to increase plants is vital for subsequent success. Seeds are mainly sown in greenhouses in late winter and spring, and outdoors in spring and early summer. Herbaceous perennials are best divided in spring. Softwood cuttings are usually taken in late spring and early summer (when soft shoots are available); half-ripe cuttings (also known as semi-hardwood cuttings) mainly in mid-summer; and hardwood cuttings from mature wood usually in late summer and early autumn, but they can be taken until late winter.