What To Plant In Your Polytunnel or Greenhouse in May

By Jorge Luis Zapico

With May, you will see an explosion in growth in your polytunnel or greenhouse. As the weather really begins to warm up, plenty of plants will put on some serious growth. This month is all about making sure that the plants you have under cover do not get out of control. One of the key things this month is making sure that your plants are not too crowded and that you take care of their main needs. Watering will need to be stepped up, you will need to use plant feeds to ensure optimum health and maintain healthy air flow to reduce the incidence of disease and pests. Insects will play a big role, even inside your polytunnel or greenhouse this month. The key is to make sure you attract enough of the predatory and beneficial insects that the pests do not get out of control.


This is the month when most growers will really begin to see the fruits of their labours. If you sowed diligently in previous months, you should have plenty of salad crops, spring onions, onions, chard, cabbages, pak choi and other Chinese vegetables. Baby carrots, peas, mange tout and broad beans may well be ready for harvesting by now and towards the end of the month you may even see the first of your indoor-grown strawberries ripening.


This is a transition month in the polytunnel or greenhouse. As you begin to harvest your earliest crops of the year, you will be making space for your summer crops, which you will be able to put into the polytunnel this month across most of the UK. Your polytunnel or greenhouse will fill up with tomatoes, peppers sweet and hot, courgettes, summer squash and cucumbers as the weather gets warm enough for them to handle.


This will free up some of the space on your windowsills indoors and allow you to get on with sowing more crops for succession planting and a few more heat-liking plants. If you plant them in a block pattern for pollination, sweetcorn can do well in a polytunnel. Sow seeds singly in toilet roll tubes. French beans, more tender than other beans, can also be sown from this month.


Though this is an exciting time and it can be great to see new crops taking their places, do not forget to continue to succession sow lettuces, radishes and other salad crops so that you will have a continuous supply throughout the year. Keep on top of weeding and whenever gaps open up, be sure to add nutrients in the form of surface dressing mulches. Look out for pests and open doors on all sunny days to make sure there is adequate ventilation as the weather warms. Do not be tempted to overfill your polytunnel or greenhouse, but do try to make most efficient use of the space you have.

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