For an extended cropping season, try sowing early, mid-season and late cultivars at the same time, or sow one early cultivar another two times, three weeks apart.
For sowing outdoors, you should be aiming for the late spring if you’re putting the seeds in the ground or in pots.
Make sure the soil temperature is above 10ºC. As sweetcorn is wind pollinated, plants should be grown in blocks rather than rows, and should be spaced 45cm apart.
Sow two or three seeds at each point, then thin out the extra seedlings to leave just the strongest one.