Tepary beans, limas, and yard longs are all different species, and will not cross. You can grow them side-by-side & still get pure seed.

Each could possibly cross with others of the same species, if they were nearby. Teparies are adapted to hot desert climates, and are not commonly grown in the North... so it is unlikely that anyone near you is growing them. Yard longs are are botanically cowpeas, and could possibly cross with yard longs / cowpeas grown by your neighbors... but this too is unlikely.

Limas are another story. Their blossoms are very attractive to bees, and if one of your neighbors is also growing limas, a cross or two is possible. My rural garden is over 1/4 mile from any other gardens, and I got a lima cross one year.

One note regarding tepary beans. Some of the varieties in circulation carry bean common mosaic virus (BCMV). Until you know if your stock is infected, I would recommend planting them some distance from your other beans as a safety precaution.

I grow the white wood aster and the mexican petunia to decoy the bees from the limas,cowpeas and yarlongs
I never see bees on them while the flowers are blooming
I only save seeds from those blooming the same time as the asters

zeedman...thank you for the info...you said you got a cross one year...how did you know that, other than planting the next spring and finding out, is there a different way to know?

Unfortunately, if a bean cross does occur, it will not be visible in the seed from that year. All of the dry seed - including any crosses - will look like the original seed. Only when the seed is planted, in the F2 generation, will any differences become apparent.

The lima cross introduced white seed patterns which were not present in the original seed, and were atypical for the variety. The plant with the white seed was also shorter in comparison to others in the row; had I been more observant of this, I would have destroyed the plant before it bloomed. I had considered a cross unlikely, since limas are not that widely grown here... but the traits of the variant suggest a possible cross with "Henderson's", or a similar bush lima.

I wonder if I got a cross with my BJBBS's ?

I am trying to keep the seed pure by planting my other Lima beans, speckled butter beans, at least 200' away. I did notice some different colors this year. Some were pure white and some were white with red streaks.

The only other garden around here is 2/10th's of a mile away.

I saved only the black seeds for planting this spring.