My wood ID skills range from "Yup, thats Pine" to "Yup, thats Aspen". So this weekend, I'm getting my pick- Elm, Ash, Cottonwood, Spruce, and Pine. The last two shouldn't be a problem, but doing the Wiki thing, I know I'll have a heck'uv a time picking the Elm and Ash from the cottonwood. What are the key characteristics I should look for? Thanks, JB