F1 hybrids, in contrast to their true-breeding parents, are not true breeding. Seeds produced by an F1 hybrid tend to develop into plants that are highly variable and generally inferior to the F1 hybrid parents. These combinations can be observed when seeds are collected from an F1 hybrid and planted. Examples of F1 hybrids that set seed easily include tomatoes, peppers, cucurbits, purple coneflowers, and black-eyed susans. A few principles must be considered before attempting to breed plants.
Some plants are tolerant of inbreeding and can be self-pollinated.
These include houseplants such as asparagus ferns and spider plants, many perennials, and vegetable crops such as peppers and peas. Good candidates for cross-pollination between different cultivars include African violets, geraniums, marigolds, petunias, and lilies. Seed fertility and viability must also be considered. Some plants may set seeds or spores that have a low germination percentage or are totally sterile. For these reasons, gerbera daisies, Boston ferns, and banana cultivars should be avoided in breeding efforts.