As summer slips gently into autumn and the days begin to become shorter and noticeably colder, there are a few jobs to be done around the greenhouse to start getting things ready for the coming winter.
Autumn is a good time for a little routine greenhouse maintenance – cleaning and repairing the structure inside and out, thoroughly disinfecting staging and equipment and making sure that the heating system is in good order before the temperature really plummets. This can be done even as early in the season as late August or the first week in September, especially if you have a lot of tender plants to protect – British weather being what it is, you can never be sure when the first frost will come, so it is as well to be prepared!
It is also a good idea to use this opportunity to clean out gutters and inspect them for leaks, either replacing or repairing as appropriate – leaky guttering can often cause the wood in timber-framed greenhouses to rot and it does little to enhance aluminium ones either. It is worthwhile keeping a regular eye on gutters and downspouts throughout autumn, especially if there are trees in the vicinity, since they can block up with leaves very quickly at this time of year.
As autumn progresses and light levels drop, any shading put up in the summer to protect delicate leaves from scorching should now be removed and if your greenhouse is on an exposed site or you keep particularly tender plants, it might be time to think about insulation.
Before the nights turn too cold, young or frost-sensitive plants obviously need to be brought in and it is a good plan to check them over at this point for any signs of pests and disease to avoid introducing any problems into the greenhouse. With the greenhouse now often at its most crowded, a careful watch needs to be kept for the first signs of any ill-health – mildews and moulds being a particular potential nuisance at this point in the gardener’s calendar.
As the inside temperature becomes cooler, it is important that any watering is done carefully to avoid making perfect conditions for grey mould (Botrytis) which attacks a wide range of plants and thrives in cool, damp surroundings – so aim for a slightly dry atmosphere. Prompt treatment can often help, but any plant which has gone too far will – sadly – need to be discarded and burnt to prevent the trouble spreading.
Even though the summer has only just passed, autumn is a good time to already be thinking about getting prepared for the next growing season. A wide range of different plants can be propagated from cuttings and over-wintered in the greenhouse to give them a head start in the New Year, including a number of tender perennial plants, shrubs, herbs, carnations, fuchsias and pelargoniums.
Sown in early September, annuals too can be grown on in the greenhouse – provided they get enough light – to provide a really colourful early display in the spring. Again, there is no shortage of suitable candidates, including calendulas, carnations, cornflowers, nemesias, godetias, phlox and schizanthus. Early vegetables can also be sown and bulbs potted up in October to give a welcome splash of colour as the winter draws to an end.
There is always something a little sad about putting the garden to bed as autumn slowly begins to yield to winter – but at least a greenhouse not only lets you protect your choice tender plants from the worst of the cold, but also get ahead of the game for the coming spring. With all your autumn maintenance and cleaning done, you should have just about enough time to pour over all those seed catalogues before you need to start sowing!