There's lots of research that says that too many choices on a screen causes more users to make no selection at all and move on because they're unsure, losing revenue forever.
Small sample empirical data: Most services I've used have 3 options on their initial sign-up page, sometimes with a call-to-action special "Limited time only!" special deal layered on top.
If you think that lots of options are part of your value, you can always get people started and happy (as per the wise advice from David and Monica above) and then offer them an expanded feature set for a small incremental price per month, so long as the copy doesn't imply that their current option is somehow lame, hobbled or incomplete: "If you have both flowers and vegetables in your garden you'll love our 'Double Growth" deal for only $3.95 more per month! And if you only grow flowers, you're already on the right plan, and thanks for joining Fertilizer.com!"
The majority of the projects I advise are in some corner of the games space, where every nuance of these conversion and upgrade issues gets studied with metrics. The same process works for any app, so long as the vision for the product drives the metrics instead of the other way around. No one likes that person who says, "Do you like this shirt? Yes? No? I can go home and change it if you guys vote and say you don't like it!"
Hope this helps!