Thanks to a forum post from a vigilant Unity user we were made aware of a bit of a slip up on our part. We found that we shipped sample trees with far too many and incorrectly placed collision objects in the subscription SpeedTree Modeler. One of the models was even shifted after the collision objects were placed! The issue has been addressed and we can assure you that future releases of the Modelers will ship with sample trees with less and better-tuned collision objects.
If you have the old SpeedTree samples and a subscription version of SpeedTree, you can easily edit the collision objects to your liking. If you need it, the documentation is here. If you don’t have the Modeler, or if you do and you simply don’t want to edit the trees, you can access both the Unity and UE4 versions of the updated sample SpeedTrees for free on our store.