To create forest alike, we mixed 4-5 tree species with a various size 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.
Our design intent is 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.
But 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 about 8-10 m.