Although in theory all subjects should make seeds from which new plants can be raised, some do not, particularly in our climate, and some are sterile because they are hybrids, the result of cross-breeding. Many of those that do produce seeds, do not pass on their own characteristics entirely. The very feature for which they are grown may not appear in their offspring. In practice, therefore, it is not advisable to grow certain perennials from seed. Nor, of course, is it necessary, seeing that vegetative propagation is reliable, quick and, in most cases, easy.
Reliable seeds of some subjects, however, can be produced by seed firms who make carefully controlled crosses, or by growing parent plants in complete isolation, often abroad in warmer climates. Even with these there may be small variations from plant to plant, generally in color or shade of color. These may be quite acceptable, however, as in alstroemerias and aquilegias, where good color mixtures are the norm. It is variations in height and habit that are most likely to cause problems.
If you do decide to gather and sow seeds more or less randomly remember that it may take a Ion time, perhaps several years, to grow plants to flowering size that plants and flowers may b variable, and that valuable time and space will be taken up before these variations will be known and the best plants selected to grow on.
