Seeds offer just about the easiest and least expensive way to obtain quantities of new plants. Nature most commonly produces new plants by seed, and plants raised from seeds are often more robust and less susceptible to disease than plants produced by a vegetative reproduction method. Many kinds of plants needed for spring and summer outdoor gardens, such as snapdragons, zinnias, marigolds, stocks, asters, and petunias, and many greenhouse plants like calceolaria, cineraria, schizanthus, primrose, and cyclamen are usually grown from seed. It is the only method of producing the annuals and biennials that flower, seed, and die in either one or two years. Most vegetables are raised from seed each year.
Seed harvested from our own plants cannot always be depended upon to produce the results we'd like. Seed from a parent that is itself a spectacular hybrid often produces unworthy or very ordinary plants. We should obtain our seed from reliable sources, that is, from seedsmen who are experts dealers who test their seeds and offer only the very best strains and varieties. Only the best quality seed is worth sowing. You must be assured of good germination so your time and effort will not be wasted.
But before you start buying those entrancing packets of seed, may I offer the voice of experience: make haste slowly. While your greenhouse is being put up, doubtlessly you are dreaming of benches bulging, shelves overflowing, and your greenhouse literally bursting with your favorite flowers: sweet-scented stock, stately delphinium, clouds of baby's-breath, gorgeous fuchsias, and baskets of trailing ivy-leaved geraniums and Campanula isophylla. Eventually your dream can come true but not right off. Packets hold hundreds of tiny seeds, and if you grow even half a dozen kinds, you may find yourself with a multitude of seedlings all needing to be transplanted at the same time. Nothing is so frustrating or time-consuming, nothing more discouraging!
So start small: the years ahead will give you the opportunity to try everything you admire.