From the FAQ's:
http://fairtradetobacco.com/links.php?ab_s=1
"29.How can I save my tobacco seed?
If more than one variety of tobacco is grown within a range of 1/2 mile, the varieties may cross-pollinate. This usually occurs from insect borne pollen. Wind pollination seems to be minimal. Happily, tobacco is self-fertile. In order to save seed of a pure strain, for yourself or for sharing with others, you should bag the bud head before the first blossom opens. An ideal fabric for a bag is a thin, spun fabric, such as Agribon-AG15. Some use organza or "wedding veil." You can sew your own bags, or purchase them from members who offer them. Some varieties of tobacco will produce a bud head that more than fills and stretches a 24"w x 30"h bag, though some bud heads are much smaller. Ideally the bud head is left on the plant until most or all of the 1/2" to 1" seed pods (there may be over 100 on a single plant) have yellowed or browned. This may require 4 or more weeks beyond harvest time. The bagged head can then be hung inverted to dry completely. It requires ~1 sq. ft to hang 1 full seed head. A single pod may contain no seeds, or up to 10,000 seeds. (Very few of the 1/4 million seeds will fall out on their own.) Once dried, the seed pods are crushed to release the tiny seeds. Dry, clean seed, in a tight container kept in a cool, dark place, will remain viable for 5 to 10 or more years."
One plant will produce plenty of seed for you to keep, trade, store for the future, etc. For safety's sake, I bag two. It's disheartening to lose the only bagged plant you have of a hard to find variety to high winds or bud worms. The most important part of selecting which plant to bag is that the plant hold "true to form" for that variety. The more plants you have of a variety, the easier it is to tell what that variety should look like. Once you know which plants hold true to form, you can then select based on other criteria such as shorter cycle, first to flower, one plant didn't seem to have as many bugs as another, etc. Selection over a period of time (several years) can influence future generations.
