Company Growing Interactive created these great apps:
Garden Plan Pro, Grow Planner, When To Plant, Planting Calendar, Janes Delicious Garden, Vegetable Planting Guide from Mr Fothergills Seeds, Tomato Chooser from Mother Earth News, Vegetable Planting Guide from Mr Fothergills Seeds (Australia), Suttons Fruit & Veg Planting Guide, Old Farmer's Almanac Planner, Homegrown with Bonnie Plants, Dobies, and others..
