Sweetcorn

I sow at the beginning of May for planting out in June.

Earlibird and Goldcrest are sh2 aka shrunken-2 aka supersweet. These need to be isolated from all other sweetcorn types. You can isolate by distance or by sowing date:

"Extensive crossing of super sweet varieties with non-super sweet varieties will cause tough, starchy kernels in both types. If you plan to grow both super sweet and non-super sweet varieties, avoid cross-pollination using any one of the following three options: 1) Plant super sweet varieties at least 300 feet from non-super sweet varieties, or 2) Stagger plantings by a 12-day planting date difference and separate each planting by 25 feet, or 3) Plant varieties that will mature at least 12 days apart and separate each planting by 25 feet." - Johnny's Seeds

Minipop doesn't need pollination to produce cobs, but I don't know what happens if it does get pollinated.