Before the SpeedTree Engine 3ds Max plugin was developed, the best way to get SpeedTree geometry into 3ds Max was by exporting a large mesh out of SpeedTree Cinema. If you wanted wind or growth animation, you'd have to export enormous point caches that were baked with fixed parameters. With the 3ds Max plugin, you'll be able to load compact procedural files (~1 MB) and generate a tree's geometry in Max with resolution, season, and wind & growth animation settings adjusted on the fly.
The plugin reads SpeedTree STE and SPM files, files that are primarily read and written by SpeedTree Cinema.
Materials, as defined in SpeedTree Cinema, are also imported into 3ds Max, detailed here.
Because SpeedTree is procedural, there are several things that can be controlled interactively in 3ds Max. These include: