To identify it, I'd go to Google, hit the "Images" tab, and type in
"Alder leaves." You should get pictures of alder leaves, and if they
look like your trees, you have your answer.

I'd probably dump the food you got and get some that doesn't stink.
Alders are pretty sturdy trees. They grow out of my rain gutters if I
don't clean them fast enough. They grow in my clay and gravel
driveway. I can't think they're all that fussy about needing special
food.