January 21: Clean your greenhouse; start sowing seeds; try root cuttings
The weather may not be perfect for going out into the garden, but there is plenty to do inside. Clean, clean and clean some more, as most plants are still dormant and the greenhouse is as empty as it ever is likely to be, so now is a good time to wash the inside of the greenhouse. Use a disinfectant such as Jeyes fluid to clean not only the glass and frame of your greenhouse but the soil too. This will help reduce the number of pests and diseases that are able to over-winter.
•When the greenhouse is clean you can start sowing seeds. Now is good to start onions, leeks and cabbages, and summer flowers such as lobelia and sweet peas. These need to be sown in clean pots and trays, give them a good wash with a suitable disinfectant to reduce the chances of fungal diseases. You will need to start the onions off in a heated greenhouse, at a temperature of 16C. You must maintain a steady temperature, as germination is slow. Sow the seeds in clean seed trays, or try cell trays filled with good seed compost. Once the seedlings are large enough to handle, prick them out very carefully into individual peat or paper pots. Transplanting is the trickiest part of growing early onions as it can make them prone to bolting later on. Once the seedlings are potted up, gradually reduce the temperature to 10C, and then harden them off the plants in a cold frame or cloche for a few days. Plant out in April in rows 30-40cm apart, spacing the plants 5- 7cm apart in the row. Plant them shallowly with a trowel, as deep planting tends to keep the bulbs small.
•Another method of propagation you can try now is root cuttings. Root cuttings are easy and a very cheap – but the number of plants that are successful from the method is limited. The ideal plants for root cuttings are Japanese anemones, Oriental poppies, Verbascum, Acanthus and horseradish. You will need to dig the plant up and wash the soil off the roots, and select roots that are around pencil thick. Cut them into lengths of 5cm with a flat top and slanting bottom, ensuring the cuttings are kept the correct way up. Insert in a seed and potting type compost that is open and free draining, and put a layer of grit over the top of the compost to improve drainage around the cuttings. Water them well and then put in a frost-free cold frame, or – better – a heated propagator. The rooted cuttings can be potted on individually when they are well established in late spring. The parent plant can be planted again as long as it still has roots. Plants with finer roots can also be propagated in this way, such as phlox, nepeta, and primulas.Prepare in the same way but lay root cuttings flat on the surface of the compost in trays and cover lightly with compos t.
•Start early potatoes chitting now ready to plant in March. Early potatoes are appearing now in garden centres or by mail order. As well as advancing the date they will be harvested, chitting them will also increase the yield. To start them off lay the tubers in a tray with the rose end uppermost that is the end with the most buds on it. Put them in a light, cool frost-free place (a spare bedroom or utility room is ideal). After two or three weeks shoots will start to appear. Thin these to two or three shoots per tuber.