Works great on my Droid. A double tap zooms a column, and reformats it to fit the screen. Not too much scrolling. I use it all the time. Can't think of a better "reference app" for gardening than this site and a browser. =)
Smartgardener.com has a truckload of info that can be viewed from the phone. The app functions of the site, especially the garden planner, don't all work as well on my phone (iphone 4) but the information about plants and their gardening manual can be viewed perfectly. They have thousands of detailed plant profiles with all the nitty gritty info you need from soil pH to hardiness zones to minimal soil temp for planting down to the variety level.
There are some other garden apps on iPhone but they are pretty bare roots so far.