To create forest alike, we mixed 4-5 tree species with the various sizes in one mound planter and set a group planting of each tree species to create a mass of form, color and/or texture of that tree species (refer the tree plan in the image below).
We divided the group planting into 3 categories, which are the group of 5-6 numbers of 3.0-4.0 m. high tree, 4-5 numbers of 6.0 m high tree and 2-3 numbers of 8 m. high tree.
In the case of those group of high trees on your attached photo stand out among other trees because we got them in over-size than our specification.
Actually, those tree should come with 6.0 m.high but TEPL was able to get only the bigger size which is about 8-10 m.
However, you will get a natural feel when all the tree settles into its shape with full foliage