they're really three different kinds of oaks. we started planting them on the mississippi river, but now anybody wants a tree, we give them to him. >> he's grown more than 725,000 trees, and hopes to reach his goal of 1 million in 2017. his secret? >> you know how to grow a good tree? give it a live love. go out at night, ooey, ooey, ooey. >> he created this nursery with a cachet ward for being chosen cnn hero last november. it was a big surprise on a special night. >> i'm humbled to be part of all this. and i'll just keep on cleaning up america's rivers and love every minute of it. >> i have so many favorite parts of my work. you can work with thousands of great volunteers. and it's very tangible.