I'm also a garden designer & think the plant database is one of the biggest red herrings in Landmark. It's talked up as a useable feature whereas in truth it's not really anything more than an electronic reference book, and a bad one at that as it doesn't contain many relevant plants for the typical domestic garden. I did spend some time converting one of the major nursery catalogues into the correct format for importing to the database, but even then found I didn't use the database as it was as quick to define a new plant from scratch so haven't bothered with that since v10.5.
I do use & teach the place plant tool though - I'd venture to say that most VW users aren't tek-savvy enough to start writing their own plant utilities, some would even struggle with adding 3rd party scripts, and so most people have to live with what they've got. The work flow of planting has improved massively in VW12 but the fragility of the file structure still makes life difficult - and as for the default plant symbols, they generally fall uncomfortably between being too bad to use for presentation drawings and too fancy to use on working drawings.
I usually advise people to define a new set of symbols, get rid of the default plant definitions and ignore the plant database!