The new plants are coming mostly from peculiar seeds. There are 4 groups of monsters. Each group drops seeds of another set of 4 different plants. Tosee which groups drops which seeds have a look at
http://uo.stratics.com/php-bin/show_content.php?content=28953 .
Since seeds now stack I would suggest to collect seeds of your desired group until you have 4 different stacks. I f you now grow one plant from each stack and if you keep track of it, you know how many seeds you have of each plant. (Some of them are more desireable and you dont have to waste poppy dust/time to grow unwanted plants.)
All those monster can drop a fragrant seed. That one produces a cocao tree.
Due to another bug (what became a feature) boglings and bog things are now dropping random seeds of every plant. The tribarrel cactus seeds are randomly replaced by other ones. best would be to read about it at the gardener profession essay on stratics. You can get that way some of the new plants and bonsai plant in coloured versions.
The naturalists quest 'only' gives out random seeds in rare colours. Those can be grwon into full plants but dont produce any seeds for reproductioning them. (That quest is still very interesting for getting rare coloured plants for the new staining/dyes system which relies on decorative plants as resources.)
