Methods and hybrid seed are provided which involve growing two varieties of a field crop which is at least partially cross-pollinated in the field, wherein the two varieties are fertile with respect to both male and female functions, are selected to yield specified hybrid(s), and are distinguishable with respect to seed characteristic(s). Collected seeds from the grown field crop are separated into fractions with respect to the seed characteristic, wherein at least one fraction is of hybrid seeds of the specified hybrid(s). For example, the parent varieties may be selected to yield heterotic hybrid(s) which are distinct and separable from the parent non-hybrid seeds with respect to the at least one seed characteristic, e.g., have larger or smaller seeds. Possibly, different traits may be used to separate the hybrid seeds from the two parent variety seeds, such as size, weight or optical parameters that enable sorting out the hybrids from the overall crop.