"OP" vs "OP"

"OP variety"
An OP variety is genetically uniform enough that it "comes true" to its parents if it is pollinated by the same variety.

That stability was achieved by inbreeding a group of plants over many generations while selecting for desirable traits, and "roguing out" (pulling) any rogue plant that lacked the desired traits.

All heirlooms are OP varieties. "Heirloom" suggests that it has been preserved for 75 years or 100 years.

To create or preserve an OP variety, you must prevent it from cross-pollinating with different varieties of the same species. Cross-pollinating would add random genes to that group of plants, so that the offspring would be unpredictable and genetically unstable.

Cross-pollination can be prevented by using isolation distances up to 1/3 or 1/2 a mile, or by bagging some blooms and then hand-pollinating them. Cross-pollination can be "mostly" prevented with much shorter isolation distances and some precautions (see below, footnote #1).

2. Hybrid Variety
The opposite of an OP variety is an F1 hybrid variety. Those require human intervention to produce and propagate. Usually there are two or more inbred "parent" OP varieties that were developed and maintained the same way any OP variety is created and maintained.

Named, marketable F1 seed is produced by carefully preventing the seed parent from pollinating "herself," while someone or something transfers pollen from the "male" parent. It can be done artificially, perhaps by plucking anthers and stamens, bagging seed blooms, collecting pollen, and manually pollinating a stigma with a small brush or Q-Tip. Insects and wind could also do the pollinating, as long as there is no other nearby source of pollen from the same species.

These F1 seeds produce F1 plants with several advantages, such as vigor, unusual bloom forms, colors, size, hardiness, or productivity that breeders can't achieve in any one OP variety.

Most seed-saving gardeners consider it a major disadvantage of hybrid varieties that the F1 hybrid plants produce F2 seeds that do NOT come true. They have a random mish-mash of traits that may or may not be anything like the desirable F1 parents.

A few seed savers like the surprise of growing out F2 or F3 generations, or randomly cross-pollinated varieties, to see what random recombinations look like. However, these crosses will also not breed true, and can only be preserved using cuttings.

By the way, this is how breeders produce and preserve patented, protected, salable hybrid plants. By cross-pollinating and back-crossing and discarding tens of thousands of "blah" plants, they produce one unusually desirable plant. Then they clone that one plant in marketable quantities (propagate it asexually through cuttings or roots, rhizomes, tubers, or bulbs). But if you let it self-pollinate, it will either turn out to be sterile or the seeds will not come true to the parent.

3. "Openly Pollinated"
The opposite of artificial pollination through human intervention ("bag and daub") is allowing plants to pollinate themselves and each other via wind and insects. This can be done with or without observing isolation distances. It might result in heavy cross-pollination, slight cross-pollination, or no cross-pollination.

If you allow F1 hybrids to pollinate themselves via wind and insect, you get a blurry mix of "probably blah" plants without the special traits the F1 cultivar was appreciated for.

If you let an OP strain do that to itself, while observing isolation distances, you propagate the desirable OP strain and can conserve all of its desirable and traditional traits through multiple generations.

If you do it with more than one OP variety close enough for cross-pollination, you get a blurry mix of the two parent OP varieties, and future generations of seeds will be increasingly blurry, generic and "NO ID."

Another way to use the "Openly Pollinated" strategy is to combine it with aggressive selection. Crossing many strains freely gathers and concentrates great genetic variety. If you eliminate 90% or 95% of all the offspring, and propagate only the individuals that have specific traits that you desire, you can "fish" in a huge genetic ocean for the few genes that meet your goals.

Freely crossing the 1%, 5% or 10% of individuals that were somewhat promising, and planting their seeds lets you "fish" next year from a pond that has concentrated many traits you were seeking. Now you may find highly promising individuals with traits that recombined from moderately promising individuals.

ATP member Joseph has been doing this for several years in a mountainous micro-climate in Utah. The climate there is a very rigorous selector!
https://garden.org/ideas/view/...

The first year that he trials miscellaneous varieties, he may get very few survivors. But seeds recombined from those survivors and survivors of other trials usually do much better their second year.

And third year seeds often do very well indeed! His locally selected "adaptivars" are neither inbred OP varieties, nor artificial F1 hybrids, nor "blah, uninteresting mishmashes". Rigorous selection combined with open pollination and maximum genetic diversity produced instead seeds that approach being a "landrace": a locally adapted population rather than a single variety, whose genes are present in ratios of diverse forms rather than homozygous (single forms).

Footnote #1 Preserving Insect-Pollinated Heirlooms

A bee CAN travel 1/3 mile or even more between visits to its hive. But it's very rare that a bee will visit a plant 1,500 feet from your yard, and then fly directly to YOUR plant and cross pollinate it. If you aren't trying to conserve a rare heirloom for posterity, or selling seeds, you don't need 99.9% purity.

Even if your "isolation distances" are only 100 - 200 feet, you can multiply OP seeds "mostly pure" by surrounding a big patch of that variety with plants of different species. It also helps to save seeds mostly from plants in the center of the patch.

Unless you need 95%+ genetic purity, you can just avoid planting the same species in the closest beds and then not worry about a few percentage points of cross-pollination. Next year, pluck any plant that lacks some obvious parental trait before it can pollinate its neighbors.

You may be able to keep an insect-pollinated heirloom "relatively pure" with row covers sealed tightly to the ground until the patch is in very full bloom, un-pollinated and then one day cover most of the nearby cross-pollinators. That night or before dawn the next morning, remove the cover from your heirloom patch to allow bees in before they have gone all around the neighborhood. Then cover it again after a few hours of frenzied pollination. That's easier than hand-pollinating hundreds of blooms!