Luis Vallejo calls this Yama momji Japanese maple. Yama is mountain and momiji is Japanese maple (Acer palmatum). So you'll sometimes hear this variety referred to as Mountain maple, which is the original, naturally occurring, non-cultivar Japanese maples. Because of the differences in the leaves, I'm guessing that this was originally several different trees that were planted very close together, rather than a clump style planting.

Yesterday we featured three magnificent maples that belong to Luis Vallejo. Turns out they are just the tip of his maple offering. Here’s a few more for your enjoyment. If you’re inclined, there are still more on Luis’s timeline

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Closeup. Some of the trunks have fused. Perhaps the three that have fused (on the left) is one tree with three trunks.

Root-over-rock Trident maple (Acer buergerianum). The Japanese name is Kaede

It's a little easier to see the rock in this closeup.

Another Trident maple. It's unusual to have a completely hidden trunk, but occasionally you'll see trees that are styled almost exclusively to show off their impressive crown of leaves. Like this one

Another tree designed to show of its colorful leaves at the expense of the trunk. Luis calls this one an Acer Palmatum Benichidori. 

Another Yama momoji Japanese maple and another impressive crown of leaves. But this time you can see the trunk's powerful base and nebari

Hedge maple (Acer campestre). A little change of pace... it's still a maple, but a much less common maple (in bonsai circles at least).

Now you can see the fern...