We look foward to May as the first month of summer but actually it marks the end of spring. In fact May can be a complete disaster month, bringing damaging frost, cold wind and heavy rain or hail. So be prepared to take steps to protect plants if it is necessary.
Sprouting broccoli, cabbage, spinach, rhubarb, spring onion, early sown lettuce, beetroot, radish and peas. Cut asparagus regularly to maintain the supply. Start removing the side shoots on tomatoes. Use up the last of the leeks. Clear away any old or finished crops, dig over the soil and prepare the site ready for the next crop.
Sowing and Planting
Sow dwarf and climbing french beans, runner beans, sweet corn, outdoor cucumbers, courgettes, pumpkins, squashes in pots or trays under glass. All these can be planted out next month.
Continue making successional sowings directly in the soil of lettuce, radish, spinach, turnips, ( switch to kohl rabi when the weather becomes hot) beetroot for summer use and also maincrop beetroot to put into store at end of the summer. Meanwhile the leeks, brussel sprouts and french beans sown last month under glass, can be planted out. This is also your last opportunity to sow peas and parsnip this year.
Thin out the seedlings of beetroot, carrots, lettuce, onions, parsnips, turnips whilst they are still very small. Always water along the row to settle the disturbed seedlings back in, once the job is completed. Put up poles for runner and climbing french beans. Support peas and broad beans before they become too tall. Start to earth up potatoes especially if a frost is forecast. Put some straw, if you can get it, underneath the developing strawberry fruit to keep them off the soil and try to avoid watering overhead to reduce any problems with mildew.
Pest and Diseases
Look out for blackfly on broad beans, greenfly on peas, lettuce, cabbage root fly, carrot fly, thrip damage on brassicas especially when the plants are small. Spray the affected plants with soapy water (diluted washing up liquid) or squash the flies with your thumb and finger. You can buy insecticides if you prefer, including a fatty acid soap on plants.