Preparing plants for cold climates

Careful planning is required to ensure your plants are prepared for the cold weather. These tips will help you get started.

It is possible, in cooler regions, to get a head start on the main growing season by germinating vegetable or annual herb seeds indoors or under glass towards the end of winter. All that is required is warmth, light and an adequately sheltered area, such as a glassed-in porch or a sunny windowsill where trays of seeds and seedlings can be kept until the weather becomes warm enough for the plants to be transplanted out into the garden.

• Sow the seeds in a light potting or seed-raising mixture as directed on the seed packet. If using small pots or trays, enclosing these in a plastic bag will help to maintain a high level of humidity and assist in germination. The seed-raising mixture must be kept lightly moist at all times until germination is completed and then watered daily until the young plants are ready to be transplanted.
• It is possible to buy conveniently ready-made mini-greenhouses for germinating seedlings, which consist of a shallow planting tray and a clear plastic lid with a vent that fits neatly on top. This allows good temperature and moisture control; the vent is opened after germination to allow air circulation around young seedlings (too much humidity after germination can cause fungal problems).
• By germinating seeds in mid-winter, then potting them up in large containers when the seedlings have reached a height of 15 centimetres (six inches), it is possible to produce quite large and vigorous plants that can be transplanted in spring. The aim is to get them to the flowering stage as early as possible, and this necessitates a good quality potting mix with extra nutrients added, in the form of a slow-release fertilizer, to boost steady growth in the early stages. Extra care must be taken as these plants must be transplanted twice — from tray to pot, then from pot to garden.
• Transplanting can easily cause a setback or slowing of growth, so to make sure that this process is not traumatic it is best to transplant in the early evening, after the sun has left the garden. Make sure that the potting soil and the ground into which tomatoes are being planted is lightly moist, and protect the young plants from direct sunlight for the first week by covering them with some shade cloth during the middle of the day.
• In climates where temperatures drop dramatically in autumn, some crops may not have reached maturity and could be damaged with the onset of the colder weather. Individual plants can be protected at night or on cold days by using clear plastic sheeting stretched above them as a barrier. With pumpkins, for example, it is necessary to wait until the stems have withered before harvesting. A few warm, sunny days may do the trick, but if not, keep them covered as long as possible.
• Any unripe tomatoes can be harvested and either placed in a warm spot to ripen or processed into green tomato chutney or jam.