Usually the risk of frost has passed by now, and with longer days there comes more sunshine and time to be in your allotment. If the weather is dry, then water your seed drills well before sowing any seeds – this way the young plants will develop a good root system.
Beetroot, broad beans, cabbage, cauliflower, early peas, lettuce, rhubarb, spring onions, radish, spinach can all start to be harvested now. Lift the earliest potatoes towards the end of the month and continue earthing up the rows of your other varieties.
June is the end of the asparagus season, so stop cutting and give the plants a top dressing of general fertiliser to help build up the crowns for next year. Start to harvest the first of your soft fruits.
Successional sowings of beetroot, kohl rabi, lettuce and winter cabbage seeds can all be done now – follow the instructions on the back of your seed packets, but it is worth starting them off in trays indoors and then transferring them outside after a couple of weeks. Sow every 2 - 4 weeks for a continual supply of produce.
Brussels sprouts, cabbages, cauliflowers, celeriac, courgettes, outdoor cucumbers, French and runner beans, leeks, pumpkins, squashes, sweet corn, outdoor tomatoes can all be planted out into their final position now. As with all young plants water in carefully and protect from birds with netting
Watch out for aphids (black fly on broad beans and greenfly on various crops) and thrips on brassicas – spray the plant 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 to spray on the plants.
Carrot fly is a particular problem between May and September – when female flies lay their eggs. There are varieties of carrots on the market that have been bred to be more resistant to carrot fly (e.g. Fly Away and Resitafly) but none are 100% proof. To deter low-flying female flies, cover plants with horticultural fleece or place two foot high barriers around the plants (plastic bottle cloches work well). A biological control (pathogenic nematodes) can be bought from mail-order companies (known as Nemasys Grow Your Own), to help control the young larvae or you can opt for chemical control in the guise of Westland Plant Rescue Fruit & Vegetable Bug Killer (Lambda cyhalothrin).
Cabbage root fly attacks the roots of brassicas. Female flies lay the eggs on the surface of the soil next to the stem of the plant. When transplanting out young plants, place a piece of carpet (or cardboard or fleece) around the base of the plant to create a collar, this will stop the flies from laying their eggs on the soil. Again the biological control (pathogenic nematodes) can be used to deal with any larvae.
Advice courtesy of The National Allotment Society