16:13 - 07 September 2010
Many greenhouse crops are coming to an end this month, but late sown tomatoes, peppers and other fruiting crops may continue well into the autumn until the first frosts permeate through the greenhouse glass. There’s still plenty to do in the greenhouse, including continuing to the harvest but it is also time to be thinking about preparing for low temperatures, lower light levels and to finish tidying up.
Keep an eye on the internal temperature of the greenhouse, if you haven’t got one, invest in a good maximum and minimum thermometer to keep an eye on nighttime temperatures.
Ventilation is important at this time of year, but it is vital to protect your plants from cold snaps. Shut any windows that aren’t automatic and only open them on hot and sunny days. Allow automatic vents to regulate the temperature unless it is particularly warm.
Bring any tender plants that have been sunning themselves on the patio into the greenhouse. Stand them on a polystyrene trays or wood which will insulate them from below against cold in the ground.
Check that greenhouse heaters are working before you need to press them into action. Ensure your power supply is working and that you have stores of fuel for paraffin and gas heaters.
Clean away dead plants and remove any dead and dying plant material.
Treat all pots and planters inside the greenhouse against vine weevil. Choose the biological control based on nematodes and apply to the compost in all your pots.
Continue to regularly harvest all greenhouse produce; some plants will keep on making new foliage and fruit for several more weeks, providing you with tasty fruit and vegetables.
Cut off the stems of tomatoes at root level and hang the plants complete with fruit upside down in the greenhouse. This will encourage the fruit to ripen. Hang a banana skin among the stems to speed ripening.
Finish drying onions and garlic bulbs in the greenhouse and then hang them up in a cool, dry dark place for easy access when you want to use them in cooking. Keep an eye out for rots and problems and be sure to use any bulbs showing signs of damage. Remove any that are diseased and dispose of them.
Keep an eye on greenhouse grapes that may be showing signs of mildew, especially in very warm weather. Spray them with water daily if possible and if the problem is bad, prune out affected growth. Keep the air flow within and around the plant as good as possible, remove overcrowded leaves and thin heavy bunches of grapes by removing every third grape. Harvest any that are ripe.
Continue sowing hardy winter salad crops such as land cress and oriental greens.
Sow hardy annuals such as sweet peas, cornflowers, poppies and others now for an earlier crop of flowers next season.
Pots of spring flowering bulbs can be forced in the greenhouse to create earlier displays and also flowers for cutting out of season.
Sow hardy biennials such as Wallflowers, Foxgloves and Sweet William into small pots of quality seed compost. Keep them in a frost-free greenhouse or cold frame to germinate and grow on. Although they will not flower this year, they will produce strong healthy blooms next spring and summer.
Take semi ripe cuttings from shrubs and roses. Choose stems that have started to ripen but are not woody and tough. Good plants to propagate at this time include Hebes, Rosemary, Weigela, Hydrangea, Pieris, Buddleia and Pyracantha. Cover with a plastic bag tied around the pot and place into a cold frame or frost-free greenhouse.
Take stem cuttings of climbers such as Ornamental vines, Summer Jasmine. Climbing Hydrangea and Kiwi (Actinidia). Root them in pots of quality cuttings compost, and place them in a sheltered cold frame or frost-free greenhouse.
Take stem and tip cuttings of established fuchsias and geraniums so that you have plenty of plants for next season. Keep them in a frost-free greenhouse to overwinter and water sparingly.
