Greenhouse Gardening

Cold frames

A cold frame is handy if you grow a lot of frost-tender plants that need hardening off before you can plant them out in spring. You can't take frost-tender bedding plants out of a warm greenhouse and expect them to acclimatize to outdoor conditions overnight. Hardening off lets them get accustomed to moving air and fluctuating temperatures gradually.

Stand the plants out in the cold frame 4-5 weeks before you expect the last frost, open the lid every morning and shut it each night. If it's going to be cold overnight, cover the lid of the frame with hessian or several old newspapers for insulation. If you don't have a cold frame, the alternative is to move plants out of the greenhouse on fine days and move them back at night for 2-3 weeks before it's safe to plant them out. Choose a spell of settled, mild, still weather to plant out tender plants.

A cold frame is also a good place to propagate hardy annuals and perennials from seed, or strike semi-ripe cuttings taken later in summer. With its lid open, use it to grow on young plants, such as polyanthus, cyclamen or winter bedding, during summer; these are plants that need intensive care but at lower temperatures than they'd have under glass. Once you have a cold frame, you'll find it invaluable for all sorts of 'overflows' from the greenhouse.
Other handy propagating kit

If you only propagate plants occasionally, you can get by just using seed trays with rigid plastic lids — unheated propagators that keep seeds and cuttings humid and protect seedlings from draughts and pests. Alternatively, make your own propagating covers by cutting the bottom off plastic bottles and sitting them over the top of flowerpots — unscrew the cap for ventilation.

In the garden, you can root a lot of easy cuttings in summer in well-prepared ground in an odd corner of the garden underneath a plastic cloche — or plant out single cuttings and push a bottle- propagator into the ground over each one.
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