At this time of year, your polytunnel may well still be in full summer production. But before long the produce of the summer such as the tomatoes, cucumbers, runner beans, courgettes etc. will begin to peter out and will be replaced with the winter planting. By now, you may well have already sown seeds to be placed in the polytunnel later. If you have – well done – these late season and overwintering crops can see you through the coldest months and perhaps even through the 'hungry gap' that lies beyond.
You may have already filled some gaps that have opened up in your polytunnel with over wintering crops such as winter cabbages, purple sprouting broccoli, kale, Asian greens or late season carrots. If you were sensible, you will have taken the opportunity as you switched out the crops to add some compost top dressing to the area, to replenish the stocks of nutrients in the soil and make sure that plants remain happy and healthy over the coming months.
Any gaps that open up as we move from summer into Autumn should be top dressed with compost (ideally a good quality one that you have created yourself using your own kitchen and garden waste). This will help to ensure that the soil is replenished and the yield from your polytunnel is not reduced as nutrients are depleted. This is just one of the important 'housekeeping' jobs in a polytunnel as we move into autumn.
Another of the jobs to think about as we move into autumn is cutting back any dead or diseased foliage as quickly as possible and making sure that all debris is removed. Plant debris left lying around the polytunnel can worsen any pest or disease problems and so it is important to keep things orderly in order to prevent plants from being weakened as the colder weather approaches.
Think about adding extra thermal mass to your polytunnel, to help keep cold temperatures at bay for as long as possible and also consider other ways to protect tender plants from the cooling weather over the next few months. Ready the horticultural fleece or bubble wrap to protect plants from the autumn chill and make sure you are ready for the first frost – which can often creep up on you if you are not prepared for it.
As the sprawling summer plants begin to be removed as we move into autumn, clear and clean paths to ensure good hygiene for plants over the winter months, when problems are often more likely to arise for plants already strained somewhat by colder temperatures.
We are not quite into autumn yet, though, and may still have some warm spells ahead. Remember to water well and ensure adequate ventilation to make sure you make the most of the last of the warm weather crops.