I was wondering if it would be possible to have a column with the number of plants you have beside each one and another column with how many you've had so that even if you have given away some plants they would be counted. It would also be nice to give an award of sorts to the person who gives away so many plants - maybe 25? The number doesn't matter so much, that's up to you. I would think this might increase activity on the forum and make the game a little more interesting. (I love it already - just thought of this idea!)
It could look something like this (in case I don't make myself clear in the description):
The "Have" would be how many you actually have in your garden right now and the "Total" would be how many you've had altogether. So, to find out how many you've given away you would just find out the difference between the two. I'm not sure what to do about those flower/plants which are trashed though. Maybe someone else could help me out with that?