The furhtest any of my characters have got in the game is Marleybone. One of my wizards has her plants infected with Explosion Gnats (rank 4) and from what I hear I need access to Moo Shu to buy the level 4 pest killer.
Any other way to deal with these, short of ploughing in the plants?
I found two more possible solutions. There are such things as gardening spell treasure cards - my wife got one in trade but her wizard doesn't have high enough skill to use it yet.
Two of my characters are affected and one had a plant die on her. Instead of ploughing it under she's going to leave it in the pot until she has the resources to look after it, then revive it. The pot cost a lot less than the seed did.