Two kinds of corn tasselling together spoil each other's kernels: sweet corn pollinated by popcorn, field or ornamental corn goes starchy, and supersweet pollinated by any other corn loses its sugar. Keep different corn types 250 feet apart or 14 days apart in tasselling.

Iowa State Extension, 'Growing Sweet Corn in the Home Garden', yardandgarden.extension.iastate.edu/how-to/growing-sweet-corn-home-garden (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'Sweet corn pollinated by popcorn will be tough and starchy'; 'Supersweet and augmented supersweet cultivars should be isolated from standard, sugary enhanced and synergistic sweet corn types'; 'Isolation can be achieved by planting different types at least 250 feet apart'; 'A minimum of 14 days should separate the tasseling time of different corn types.'

Iowa State Extension, 'Growing and Harvesting Ornamental Corn', yardandgarden.extension.iastate.edu/how-to/growing-and-harvesting-ornamental-corn (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'Isolate ornamental corn from sweet corn and field corn to prevent cross-pollination. Isolation can be achieved by planting the different types of corn at least 250 feet from one another'; 'A minimum of 14 days should separate the tasseling times of the different types of corn.'

Illinois Extension, 'Corn' (Home Vegetable Gardening), extension.illinois.edu/gardening/corn (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'Supersweets (Sh2) should be isolated from any other type of corn tasseling at the same time to ensure sweetness and tenderness'; 'Supersweet varieties pollinated by standard sweet corn, popcorn or field corn do not develop a high sugar content and are starchy'; 'Their pollen is weak and easily supplanted by other types, which causes the kernel to revert to a form with the toughness and starchiness of field corn.'

Utah State University Extension, 'Classes of Sweet Corn', extension.usu.edu/vegetableguide/sweet-corn/varietal-selection (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'All sweet corn varieties should be isolated from field corn by 250 feet or 14 days' difference in pollen shed (tasselling dates)'; 'Isolate shrunken-2 varieties from standard and sugar enhanced types to minimize starchy kernels'; 'While isolation of sugar enhanced from standard types is not necessary, it does ensure full expression of the different sweetness characteristics.'

UMN Extension, 'Growing sweet corn in home gardens', extension.umn.edu/vegetables/growing-sweet-corn (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): Shrunken (sh) 'Isolate from all other sweet corn types. Cross-pollination between Shrunken (sh) and any other types will result in starchy, tough kernels'; Sugary (su) 'Isolate from Shrunken (sh) and Synergistic (sy) types' - the stricter line, recorded and not enacted.

UMN Extension, 'Growing popcorn in home gardens', extension.umn.edu/vegetables/growing-popcorn (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'Because popcorn takes a month or longer than sweet corn to mature, it is best to plant the popcorn first'; 'Wait three weeks before planting the sweet corn. The popcorn should produce tassels and silks before the sweet corn.'

NC State Extension, 'Organic Sweet Corn Production', content.ces.ncsu.edu/organic-sweet-corn-production (fetched in-container 2026-09-02; read by the maintainer 2026-09-02): 'If sweet corn is planted downwind of popcorn or field corn, kernels will be starchy instead of sweet.'