I checked on buydebug for those two plants, and they weren't there. Could have missed, but don't think so, searched several times for it, but...
I don't have any other store worlds, if they have plants on there, but not showing it, that is why. Strange though, you could have a sim collect it that town, move her to the town where the garden is and plant it. You would have to make it a residence and then change it back to community, but is doable.
Guess I'm going to have to hunt them up if I want them in my community garden and see if I can transfer them to my community gardens.