"I saved seeds from pink-flowering sweet peas hoping for another batch of pink-flowering plants, but all I got was white flowers!" Or, "I carefully saved the seeds from Coleus 'Flume' (Solenostemon scutellarioides 'The Flume') but these plants are way too tall and nothing like the Coleus 'Flume' I had last year." These two questions are both asking the same thing: why don't the plants I grew from seeds I collected look like the plants I got the seeds from?
The most exciting thing in the world is sexual reproduction. Birds do it, bees do it, and plants do it. I'm talking about when plant genetic material combines and recombines to produce a brand new, unique plant. Without sexual reproduction, plants would all be clones. With it, we get different colors, different cultivars, different foliage, and ultimately, different plants. Sexual reproduction (meiosis) is explained in more botanical detail here by LariAnn Garner.
But what if we want exactly the same plants that we had before? Easy, but you'll have to buy them from a seed hybridizer or someone who has the patent. Hybrid seeds are generally those for which the natural process, where female bits and male bits combine to produce a new individual, is forestalled by controlling which female bits are combined with which male bits. In Angie's excellent article about Corn Detasseling, she explains how the male bits, in this case the tassels of the male plants, are removed from corn growing in a field to make sure the female bits are fertilized by only those male bits which the hybridizers wish to use to produce corn.
That's "hybrid vigor". That's why seed companies get the big bucks. For us, home gardeners, it can be frustrating or hard to understand the process and why the plants from the seeds we saved don't look just like the plants they came from.
The plant you wanted to replicate by saving its seeds represents only half the story. There is another parent plant which you might not remember is providing half of the genetic material to create your new plants. If you want your new or next season plants to look exactly like their parents, you need to clone them. Not some science fiction fantasy or Michael Keaton in Multiplicity (picture left), cloning a plant occurs when you stick a sprig of impatiens or coleus in water by the kitchen windowsill and roots form and you pot it up. You may have never thought of it that way, but you're cloning. Same with dividing an iris or a daylily into daughter plants or dividing a dahlia tuber. Or starting potatoes from seed potatoes. Those are all examples of cloning.
But when you save seeds from year to year, as Jill M. Nicolaus discribes in this article, you are participating in the wonderful plant-driven process of sexual reproduction, where two different sets of genes combine to create a third, new combination. Plant companies often specify "seed-propagated" (as opposed to "cutting propagated") for the plants they sell. Recognizing this important distinction will help you make wiser choices.
"Seed-propagated" plants are plants that will breed true from seed. Often they will be easier to grow from seed and will not change if allowed to pollinate in the wild. It is more cost-effective to grow from seed, as you surely have noticed when comparing the cost of starting annuals from seed to the cost of buying seedlings.
"Cutting-propagated" ones are often the newest varieties, species that have a high tendency to throw sports (such as coleus), and patented types (the ones that say "vegetative propagation forbidden"). Rosy Dawn Gardens, for instance, says "All of the Coleus sold by Rosy Dawn Gardens are propagated from cuttings. We do not sell seed-grown varieties." Likewise, seeds are often advertised as "Hybrid! New! Improved!" This simply means that the reproduction for these seeds was carefully controlled, as described in Angela's article.
However, when you allow any plant, whether coleus, sweet pea, heuchera or basil, to "go to seed" or "bolt," you are introducing the random element of sexual reproduction. The seeds you started with were probably hybrid, if you bought them new, unless they were "heirloom." Without carefully controlling precisely the combination of genetic elements which go into making your seeds, you're going to get a different plant.
In the case of sweet pea seeds that bloomed the wrong color, the parent plants may have been male, pink and spindly, female, white and climbing to produce a pink, climbing plant. When you collect the seeds, you don't know which genes are dominant. In the case of saved coleus seeds, coleus is usually propagated by cuttings. Coleus ‘Flume' is actually a patented cultivar. While I doubt the plant police are going to come hunt you down, wild-pollinated seeds are definitely not going to look like the plants you purchased to begin with.
Armed with this information, you will be able to understand what's happening when you save seeds. One thing is always true: seeds you save yourself are free!
picture of white sweet pea bloom is courtesy of Lester Luallin at Flickr.