Cabrita, maybe in your location there is a pollinator insect that especially liked your pea flowers?

It's generally said that legumes pollinate themselves before the flower opens, but if there is an insect specific to your area that worked the flowers afterwards, you could have more cross pollination than growers that don't have that insect. You might have to bag a few plants if you want to be able to save seed without spraying.

That said, when I saved pea seed, I also thought that the second generation was more like shell peas than sweet peas. Maybe I should try growing only one variety of snow or sugar snap peas and see if the second generation breeds true. Maybe we are buying hybrid seed and the second generation is reverting.

You are right about pollinators happy. My neighbor on the back raises bees. The bees come to eat at my garden a lot, I don't mind a bit, we both benefit (and the bees!). In any case, i do not doubt that we have pollinators.

The strange thing to me is that the snow peas appear to all have come out true to their parents. This past weekend I examined their flowers and could not tell them apart (the snow pea flowers and the sugar snap flowers). One thing I noticed different is the maturity dates, the sugar snaps are latter. Their flowers look like a replica of one another, so why only one crossed? did the bees only go for the sweetest one? but no, they must have pollen from both in order to cross them. Hmmmm.......pea mystery.

The lesson to me is: interplant snow peas if you want, the seed will probably come true. However, if you want to save seeds from the sugar snaps, plant them separately! I saw that I still have some of the original seed, so I am planting them on their own trellis next winter. It is too late for us to plant peas now.

Throw a piece of nylon French tulle over the one from which you want to save seeds. Bees won't be able to get through it. This fabric, which can be found in any fabric store, comes in geen color as well.

Cabrita, lucky you to have a beekeeping neighbor!

I know this is a super old thread, but figured i'd comment anyway since i'm in a pea mood today. I highly doubt your peas crossed even with pollinators present. They simply are not attracted to pea flowers. Even if one flower happened to be bitten open by a solitary bee and cross pollinated with the other (1 in 1,000 chance maybe, even then it's iffy) then that still would not explain what you are seeing.

What i suspect is that you are seeing environmental influence. One of the fiber-less genes commonly used to breed snap peas is heat-influenced. I think what that means is that to get snap peas from those type you need high-heat and in cooler conditions you would get more peas that are more like shelling peas.

https://www.youtube.com/watch?v=J9pYKgt0VHo

The relevant slides start at 16:38.

Just to add-- I grow a lot of peas, and while they don't seem to be bees' first choice, I haven seen carpenter/bumble bees seeking out the blooms deliberately. (I do grow a lot of old-fashioned tall types with purple flowers, so that might possibly be a bit more appealing to the bees.)

Thanks @sea_kangaroo, yeah, which is why i said it's possible for a solitary bee to do so. but it wouldn't affect her whole crop. Last year i had quite a few bean crosses happen and bean flowers are pretty similar to peas so either a solitary bee bit into a bunch of them or some hummingbirds were at work. Honey bees can do it to, but it's even more rare for them.