Sustainability is a strong movement in agriculture and in gardening, growing stronger as the world faces economic uncertainty. The idea behind sustainability is a gardener or farmer’s being able to raise crops using only the materials he/she has at hand, according to strict definitions. Others give some leeway, allowing purchase of some fertilizers or seeds.

If you garden with an eye on sustainability, you’ll treasure your compost and save your own seeds from open-pollinated plants (not hybrids). Saving seeds is easy for many crops such as tomatoes, peppers, peas, lettuce, spinach and beans, but it’s harder to save squash or melon seeds because of cross-pollination, and to save seeds of biennials.

Here’s where it really pays to know the botanical names of what you’re growing. Squashes, for instance, all belong to the genus Cucurbita, and to one of six different species. C. maxima includes pumpkin, banana, buttercup, hubbard and marrow squashes, and they’ll cross with one another. C. mixta varieties that will cross with each other include Cushaws (except the Golden Cushaw). C. moschata includes Golden Cushaw, butternuts and cheese squashes and some others. C. pepo includes the acorns, cocozelles, crooknecks, scallops, vegetable marrows, gourds and zucchinis.

Suzanne Ashworth’s “Seed to Seed” names all of the squashes in each category if your seed packet doesn’t identify species. Or run an Internet search for the species.

There is supposedly no crossing from one of these species to another, but there may be some between C. moschata and C. mixta. To be sure of no cross-pollination, you could hand pollinate either of these that you want to save seeds from. At that point you will gain more admiration for bees and be less tempted to use long-lasting Imidacloprid on shrubs and trees that have blossoms at some time in the year.

Quirks in weather may push plants such as carrots, onions or Swiss chard into flowering and setting seeds in their first year, rather than their second year, when they should go to seed. The year I planted onions in the fall, they saw many changes in weather and by spring each was setting seed. When onions set seed, it ruins the bulb. When shallots bloom, preparing to set seed, the flower stalk forms apart from the edible bulbs and may be removed.

Carrot varieties such as the white or purple (closer to wild) may bloom their first year, sort of a birds nest of carrot seeds, although most wait until their second year. Some potatoes (but not all varieties) will set seeds too. They have attractive small blossoms (some have blue, purple and some are white) that form marble-sized balls of seeds. When these seeds are ripe, the seed pod will be soft to a squeeze, and may be harvested and cut open to release the tiny seeds.

Save those seeds by fermentation, like you do the tomato seeds. Viable seeds sink, others float. These seeds are smaller than tomato seeds though, so you’ll need a very fine sieve to wash them without losing them.

These balls of seeds are toxic members of the nightshade family, and would even taste terrible, but some gyp companies advertise “combination potato and tomato plants,” referring to the seed case as a “tomato.” Do not eat that seed ball.

These saved TPSs (True Potato Seeds) are free of disease and can be grown in one season to small tubers that can then be stored (probably in the hydrator of your refrigerator) until the following spring, and then planted out to yield a normal potato harvest. They do not run true to parental color, shape or size, but they’ll be good healthy potatoes.

Margaret Lauterbach: melauter@earthlink.net or write to Gardening, The Idaho Statesman, P.O. Box 40, Boise, ID 83707