Now? Taking trash has been a crime for a long time. Dumpster diving, for example, you're literally taking the stuff they threw out, but it's illegal to do so. This is trash that's still inside the store, I'm not surprised they don't like it (but I don't agree, at all).

I imagine staff regularly pick then up themselves to private either for the garden itself or for the garden to sell.

So if guests "steal" them, it's likely the garden then gets less funding overall.