I purchased the Grasswald Assets grass pack a while ago. I wanted to start using it more regularly but having to set up the materials was always a pain. I didn't buy the full plugin so I don't know how they set up the materials with Cycles. I made some best guesses and came up with this material here. I created a node group where all I have to do is plug-in the textures and dial in the age of the grass.
The problem is that it doesn't work very well for the blended age, works great as a toggle if all you want is new grass or old grass. If people would like to test it, that would be great and if you have any ideas on how to make it work better, let me know.
To use the material, just append the grass that you want to texture from the Grasswald assets (works with the weeds too). Assign the "Grasswald-Octane-Grass" material to the grass. Then open up the textures into the "Image Tex" nodes. The two color (Albedo/Diffuse) (new and old) must also be opened in the two "Alpha Image Tex" nodes so the node group can get access to the alpha textures in them.
In the controls on the "Grasswald Grass Tex" group node, "Transmission" controls the amount of transmission through the grass. "Age" controls the blend between the new grass texture and the old grass texture.
If anyone has a better idea on how to handle this, please let me know. I have tried about every method I can think of, including using the layer nodes, but it has similar issues to just using the "Mix Tex" node.
Here are some images of the results I'm getting...
This last image is at 50% of the new grass texture and the old grass texture to give you an idea on how badly it works.
Jason