I just looked at your “Field Grass Package Vol. 1”. Refer to the image of the grass where it looks really dense. This is what I’m aiming for
Those are all 8 tri meshes + placed with a high density 
How high a density exactly?
Wouldn’t it be better to create high tres meshes and place them with lower density?
With a brush size of 100 I used a density of 4000 -> yep you can also use high poly meshes, but imagine the case when you want to just place one single grass patch. With single grass patches you can easily create larger patches in the engine (but that’s not possible vice versa)
When you create these foliages, do you make the planes in a 3d modeling software (like blender) or do you just create them inside the UE4?
You should do everything in your 3d tool -> because you will have to do uv mapping, you might need a collision, you need lod’s you probably also need lightmaps (when you use static lights)
You just create the material in the UE4
This is 2 planes combined, with a tris of 64, using the foliage brush at size 50, with a density of 10.000:
://i.imgur/30A3MxG.jpg
I managed to create the model in Blender, and apply the material in UE4. It looks amazing. Now I just get an error when building lightning. It tells me to lower the lightmap resolution, so I’m trying that. Will report back 
After that you could also add various effects in your material -> e.g wind, colour changes,…
And how does one add wind?
You will have to do that in the material -> there you can find some wind nodes: (basic one) Use the one in the video or the flipbookwind node
The wind looks really nice. Now what about tress. How does one create these? I guess you’d create the branches and the trunk as a cylinder, then add planes to the branches and apply the leafs as material to these planes? And I guess the bark would be created using a normal map?
Other than that, I tried lowering the lightmap resolution, but still get an error, and the grass looks like the image below:
Any idea on how to solve this issue?
Which kind of error do you get?
- take a look at this thread: https://forums.unrealengine/showthread.php?68384-Lightmap-too-large-warnings
- your lightmap is overlapping -> you will have to create a proper lightmap in your 3d program ->