I learned:

It will almost never work if you do it when they’re leafed out. You have to do it when they’re dormant. So, dig them up after they’ve dropped their leaves this fall. Or, you could wait until spring and get them before the leaf buds have opened.

Aspens are almost always connected to adjacent aspens. They’re just individual stems coming up from an extensive root system. When you dig one up, you’re going to have to sever the tree from the main root system. Therefore, it’s hard to get a decent amount of root with the tree you want. This makes it hard to transplant them successfully.

Don’t try to transplant a tree taller than about five feet. Smaller aspens are easier to relocate. They won’t experience as much shock. They’ll also grow faster and surpass a larger tree you transplant.

Finally, don’t try to dig them up from dry, rocky ground. Most of the dirt will fall away from the small amount of root you manage to save. Find a place with small trees in a wet meadow—like near a beaver pond. It will make everything much easier.

When you plant the trees at home, it’s best if they’re not exposed to the hot afternoon sun.