Edible August! Yes – growing in August is all about cutting, cooking and scoffing the homegrown goodies you’ve been growing this season… Runner beans, Marathon Calabarese, Oarsman Leek, Javelin and Archer Parsnips or Sun-GOLD tomatoes (sorry about the flimsy link to Olympic related vegetables).
The Importance of Ventilation When Growing in August
In “normal” summers, Polytunnels can get really hot when the sun comes out so good ventilation is the key. Our 16ft x 30ft Polytunnel has side ventilation and ventilation screen fitted to one side. Good ventilation and air flow are key to good productivity in a greenhouse, and at no time of year is this more important than in August, when temperatures are at their highest and plant diseases such as blight can be rife.
The side ventilation option available for polytunnels consists of a piece of timber clamped to the outside of the polytunnel frame around 3ft up from the ground, from which a ventilation net is hung. The ventilation netting is either trenched, or attached to the base rail. A ventilation screen on polythene is placed outside the netting, which can be lowered or raised from the timber rail as and when it is required. With such a system of side ventilation installed, polytunnel gardeners can have far more flexibility when it comes to airflow, providing more when it is needed in August and throughout the summer, yet still protecting plants from wind chill when more protection is needed.
Whether or not you have opted for side ventilation in your polytunnel, you can still take measures to allow for good air flow when growing in August. Doors are of course vitally important, and ventilation should have been a key consideration when you chose the doors for your polytunnel.
With the added benefit and versatility of sliding doors, a good draft blows through the Polytunnel keeping the temperature controlled. Whichever doors you have on your polytunnel, you should have gone for doors at both ends. When doors at both ends of a polytunnel are opened, this allows for door through-flow of air, which can help keep the structure cool.
If you find that the natural ventilation in an existing polytunnel is less effective than you might wish, you could consider retro-fitting extra doors or extra ventilation in the polytunnel sides at a later date.
When planting, take care not to try to cram in too much. Overcrowding your plants can lead to problems with air flow and ventilation which can make plants more prone to disease and more likely to succumb to various problems. In addition to providing for growth at the point of sowing or planting, practising good pruning and crop management can also allow for good airflow to and between your plants. Make sure that you prune perennial plants to keep them in check, and take other measures (such as stripping lower leaves off squash or tomato plants, for example) in order to maintain adequate airflow between your plants and keep everything healthy and happy.
On very warm days, you can also damp down floor and other surfaces with water. This helps with humidity and has a cooling effect! Damping down is the process of raising the humidity in the polytunnel by means of wetting pathways, staging and any seating areas or areas of hardstanding. (If you have an overhead sprinkler irrigation system, this may be especially easy to achieve.) This will improve conditions for your plants and can also help make conditions less favourable for pests like red spider mite, which like very dry conditions.
Keep Pests Away
Polytunnels are wonderful growing environments for plants but the protected conditions can at times encourage unwanted pests. It’s a good idea to grow pots of basil beside the tomatoes to help keep whitefly at bay and it works a treat! French Marigolds and nasturtiums also repel whitefly and keep greenfly away from other plants so it’s worth planting both to help in the battle to keep pests away from Polytunnel crops.
When growing in August, it is important to keep a close eye on your polytunnel, and to remain vigilant for any unwanted creepy crawlies. Remember, attracting a range of beneficial wildlife is crucial for pest management in a polytunnel – August is a time when pest predating wildlife is particularly useful, so make sure you do what you can to encourage these useful creatures into your space.
See the following links for more helpful Polytunnel growing guides.
Sean Barker is the MD of First Tunnels, and is enthusiastic about providing quality gardening supplies to gardeners across the UK