Cabbages, cauliflowers, sprouts, and broccoli
May is probably the last month for sowing Brussels sprouts if you want them ready by the end of the year. The same goes for cauliflowers and cabbages (except for next spring’s early varieties). Sow them all indoors or out, depending on the weather. Some can be sown in a temporary seedbed and transplanted later in the year when space becomes available. You can keep sowing sprouting broccoli and calabrese until July.
Cauliflower seedlings raised in a length of guttering
Courgettes, pumpkins, and other squashes
Sow seeds indoors to guarantee that they germinate successfully. Plant out seedlings next month.
Florence fennel and kohl rabi
Sow some of each outdoors this month – fennel only when the soil is really warm enough for seeds to germinate. Reserve a few seeds for a second or even third batch later in the summer.
Leaf vegetables
Continue to sow kale, spinach, Swiss chard, and Oriental leaves such as mizuna, mibuna, chop suey greens, chinese broccoli, and mustard greens. They can all be sown outdoors now, although prepare to cover them on cold nights.
Oriental chop suey greens sown as a cut-and-come-again salad crop
Peas
Continue to sow maincrop peas, mangetouts, and snap peas outdoors, protecting seedlings with cloches or nets if necessary.
Melons
It may be warm enough this month to sow seeds outdoors in a cold frame or under a cloche. If not, sow indoors and position where it is warm, such as on a sunny windowsill or in a heated greenhouse.
Sweetcorn
Sow sweetcorn directly outside now. Always sow in blocks rather than rows for successful pollination. Protect young seedlings from frosts and also from attack by slugs and snails with cloches made from upturned plastic drinks bottles.
Chillies, peppers, and cucumbers
To be safe, continue to sow chillies and peppers indoors. Outdoors, even in May, seeds may not germinate. Cucumbers, however, can probably be sown outdoors under a cloche or in a cold frame.
Sowing sweet pepper seeds in a cell tray
Endive and chicory
It’s still best to sow endive and both sugarloaf and radicchio forms of chicory indoors in the warmth; they can be hardened off and planted out in June or July. However, Belgian or Witloof chicory can be sown directly outside now.
French and runner beans
Continue sowing seeds indoors if the weather is still cold or unpredictable; outdoors if the soil has warmed up and there are no longer any frosts. If necessary, protect young seedlings with cloches or plastic bottles.
Sow beans direct outdoors only when the weather has warmed up
Herbs
Succession sow further small batches of seed such as basil, coriander, chervil, dill, lovage, parsley, and sorrel. Young plants that are tender or half-hardy, such as basil, may still need protecting with cloches or covers.
Root vegetables
Carrots, beetroot, swedes, and turnips can now safely be sown outdoors. Beetroot, whose seeds can be notoriously hit-and-miss to germinate, may need covering with cloches if the spring is poor and the soil is still cold and wet.
Lettuces and other salad crops
Sow more lettuce, rocket, land cress, summer purslane, corn salad, and other salad leaves outdoors this month to ensure a steady supply. Sow under cover if the weather is still cold.
Sow outdoors under cover
Beetroot
Cucumbers
French beans
Runner beans
Sweetcorn
Sow outdoors
Beetroot
Brussels sprouts
Cabbages (summer, autumn, winter, and red)
Calabrese
Carrots
Cauliflower
Chicory (Belgian)
Florence fennel
French beans
Kale
Kohl rabi
Lettuce
Oriental leaves
Peas
Radishes
Rocket
Runner beans
Salad leaves
Spring onions
Sprouting broccoli
Swede
Swiss chard/ Spinach beet
Turnips
Sow indoors
Cabbages (summer, autumn, winter, and red)
Cauliflower (summer and autumn)
Chicory (sugarloaf and radicchio)
Chillies and peppers
Courgettes and summer squash
Endive
French beans
Kale
Marrows
Pumpkins and winter squash
Runner beans
Sprouting broccoli