Blossoms are often the Rodney Dangerfields of garden, field and forest harvests. Tomatoes, squash, beans and even corn, oats and wheat begin productions with blossoms. But not all blossoms become fruit of their blooms.

The blossoms of many plants, including corn, squash, cucumbers, walnuts, winterberries, oaks and hemp come in two kinds. About half of the blossoms become fruits and the other half only produce pollen.

Sometimes, as in corn, both flower types are on the same plant. Other times, as with hemp and winterberry, the two flower types are on different individual plants. Although we...