To the plant, pollination is pollination. To the gardener who wants particular results (such as wanting to keep an heirloom variety pure), cross-pollination (cross-breeding) is something to avoid. To a grower or scientist who is trying to create a new variety, cross-pollination is desirable. It's all on your point of view. Like Dave said, some varieties are very genetically stable, like his Nantes carrots. Others, like curcubits, are notorious for cross-pollinating. If you're growing certain kinds of decorative gourds, and zucchini or other squashes, insects will cross-pollinate them very easily, and if you saved the seeds from your wonderful zucchini and planted them, they could end up being something almost unrecognizable and tasteless. "Does cross pollination always create a hybrid?" Yes and no. Technically, every pollinated plant is producing a hybrid, because every plant from every seed has a tiny, microscopic difference from the plant next to it, although it is, for most purposes, the same. Only cuttings, cloned or tissue-cultured plants are exactly the same as the parent stock. Plants labeled 'hybrids' have been crossed from plants with noticeably different qualities. If you crossed two of these 'hybrids', they would most likely revert back to the qualities of one or the other of the 'parents'. Granny Smith apples came from crabapples. If you planted a Granny Smith seed and nutured it for several years, you would probably end up with some sort of crabapple or similar variation. Two additional bits of info (just to confuse you a little more ;-) ): 1) You can be growing two similar plants near each other, but if they flower at different times, they won't (can't) cross-pollinate. Corn is a good example: there are early, mid-season and late varieties of corn. Corn cross-pollinates easily because it's wind-borne, but if they tassle (the 'flower') at different times and there is no other corn around (esp upwind), they won't cross. If Alfie's apples (above) needed a pollinator variety, and he accidentally planted a variety that bloomed a month after his Macintosh, he wouldn't get any apples. 2) OP varieties can be 'manipulated' even within the variety. You can have a packet of seed of a single variety of an OP plant, and each seed inside will have a tiny difference about it. Many people will grow a particular variety that they like, and they will watch for 'special' ones among that variety: a tiny bit earlier, a slightly larger fruit, a sweeter flavor, a slightly higher yield, etc, and they will mark it and let a few fruits of that plant mature and collect the seed. The next year, they plant that seed, and again look for 'special' plants. Every year, they keep doing this, and end up (hopefully) with localized variety within a named variety that is especially suited to their local conditions. It's still the same variety, it's still OP, it's just an improved variation within that variety. If you bought seeds from a grower in BC, and you bought the same variety from a grower in ON, the local seeds might produce plants that had a slight edge on local conditions, concerning earliness, adaptibility to hot summers, or ability to grow with a bit less water. The seeds from BC might adapt better to cooler summers, more humidity, and a longer season.

Given you have a plum nearby and probably more plum/pluot in the area, I'd plant the best fruit and hope I didn't have to thin too much. Flavor Grenade over sets enough to be a royal pain so don't worry about it. Geo Pride also sets very well. Those are my favorites of the ones you mention. Dapple Dandy isn't very sweet and I don't care for the flavor or texture. Emerald Drop sets very well but isn't as good as several others. Flavor Supreme rates with Flavor King as the best fruit but doesn't set well and bees only visit by mistake. I don't know why they say it would pollinate anything. Flavor King, along with Supreme, has the best flavor of any pluot or plum. King sets well but not as much as most. Flavor Finale has very good flavor but doesn't hold really well on the tree or off. My favorites are: Supreme, Pride, King, Finale, and Flavor Treat which isn't widely available.

Yup- caerulea. Get one & use it as a polinator- even better get 2 as they're not self fertile. I have a load of caerulea seeds- I could send you a couple if you want to go that route. I've been trying to polinate my altocaerulea for years.. Nothing works. And yes be carefull digging up that alata- keep as much of the rootball intact & undisturbed as possible- Frankly if it were me I'd be afraid so I wish you luck.

Since pepper flowers are capable of pollinating themselves, chaances are they they get pollinated soon after they open, before a different cultivar can cross with them. It is already fairly rare. To guarantee that crosses do not occur, you can bag the blossom with any number of materials. I have heard of people making little bags out of toole (a type of fine netlike fabric). You could probably also use some sort of women's nylons. Don't use a plastic bag though, as it may overheat and it traps moisture. As soon as the flower shows signs of a pepper, you can remove the bag, just mark the pepper to ensure you remember which one it is.