Sow Sweetcorn in pots in the greenhouse this month, they will produce strong plants ready to plant out in June.
Courgettes, Marrows and outdoor Cucumbers can be sown in situ from the middle of the month provided the weather is warm enough, if it is still a bit cold start them off in the greenhouse or on your kitchen windowsill, or plant them out and give some protection with Fleece or a Cloche.
Make sure you keep all emerging seedlings and young plants well watered. Sweetcorn is wind pollinated and best planted in large blocks, so the male flowers at the top of the plant can pollinate the female tassels lower down.
If you are gardening in the north of the country, bear in mind you may need to sow everything a bit later - be led by the weather and the condition of your soil, not what it necessarily says on the packet.
Please don’t be tempted to transplant outside too early, there is nothing more disheartening than growing lovely little plants only to have them wiped out by a late frost – it could put you off growing forever - so be warned! If in doubt wait a week or two.