That's true of almost all hybrid varieties, "seedless" or not. For naturalizing vegetables, it's best to stick to heirloom/open-pollinated varieties. If planting more than one type of plant that can cross-pollinate together (all the squashes go *crazy* with that, for example), you'll end up with interesting crosses a few generations down the road, but this kind of cache gardening would lend itself extremely well to the preservation of heirloom varietal characteristics, since each cache of tomatoes, for example, could contain just one variety.

With fruit trees, be sure that you're either planting self-pollinating, or that you're planting more than one compatible variety. Be aware that if you're planting out nursery stock fruit saplings, they're almost certainly grafted onto a different rootstock, and if bad things happen to the tree, it might regrow from that rootstock and you'll end up with something completely different – possibly something that doesn't even produce fruit (much).