I HAVE SOLVED THE TOMATOES.

With help from renenet in the comments to my last post, I have worked it out:

POSITED: Tomato plants are 'spontaneously generated' from unicorn dung (which is of course to say that unicorns, dimension-hoppers that they are, eat tomatoes elsewhere and excrete the seeds in Camelot).

ALSO POSITED: The fruit of unicorn-shit-plants is clearly unfit for consumption by man or any tame beast, yet neither can the plants be uprooted.

THEREFORE: What we see as perfectly edible (and anachronistic) tomatoes are a nuisance-fruit which can be used only to throw at people in the stocks!

\o/

now for something completely, as they say, different.

I have made an important authorial decision (after review of relevant canon) about the yet-ANOTHER-Castiel-story I'm writing: ( very, very important decision. yes. )