Maggi, I understand that this is a common problem with Acer griseum. While most trees are prolific seed producers, very few give rise to viable seeds. The seeds for my seedlings were collected in a public urban area from a tree that has hundreds of seedlings underneath every year. They all get mowed down early on. The only other maple species in the vicinity are Acer truncatum and Acer platanoides. If my strange seedling is a hybrid, it will be with one of those two as the father. I will post more pictures when the leaves expand.