UPPER POTTSGROVE — The warm, wet weather has lots of folks thinking about their gardens and their yards. With that in mind, Green Allies, the student-driven non-profit organization that operates out of the Althouse Arboretum off Gilbertsville Road, held a plant sale on May 11. But these were not just any plants. It was a sale of native plants, which can help keep out invasive species, as well as provide food and shelter for the region’s native f…