Thank you Gill !

That is what I do at the moment, but I'm not really happy with it ...   on the one side there is the huge polygon count which is not necessary for trees far away (which results in backdrops or alpha planes as workaround) on the other side it's not flexible enough (for me ). But as far as I see the plant editor in Infinite or xStream is the same as in Complete; so a update won't work for this.