Plant 12 inches apart and arrange in blocks of at least 4 rows for proper pollination which is needed for well filled ears. If you lack sufficient space for enough plants for good pollination, try hand-pollinating by cutting off the tassels and shaking their pollen on the silks.Sweet corn is ready 18-24 days after the first silks show, the exact time dependent on the weather in the interim. Press ears 2 inches from the tips to assess kernel fullness. Harvest when the kernels are plump, soft, tender, and filled with a milky juice.