This hybrid of the locally introduced Kalkora Mimosa (Albizia kalkora) with the abundant Silktree Mimosa (A. julibrissin) is naturalized in a small area on and near the Duke University campus in Durham, North Carolina. Discovered in 2006 by Dr. Mel Turner, these apparent hybrids are frequent along Towerview and Circuit Drives at Duke. Indeed, the majority of trees in the area seem to be intermediate between the two species. This hybrid is likely found at N.C. State University also. I have seen saplings bought at an N.C. State plant sale that were labelled as Kalkora Mimosa, but appeared to be intermediate.

Durham, NC 9/11/08.

The leaves, flowers, and stature are all intermediate between the two species. The hybrid grows to about 40 feet tall, and has larger leaflets, with fewer pairs of branchlets on the rachis (~8-10) than Silktree Mimosa. Kalkora Mimosa grows to 60+ feet tall, has even larger leaflets, with fewer pairs of branchlets on the rachis (~6 vs. ~12 for Silktree), and rough bark.

Durham, NC 9/11/08.

The hybrids are a little tricky to ID without the full species alongside them. This photos shows the leaves of a hybrid at left with a Silktree Mimosa at right.

Durham, NC 9/11/08.

Durham, NC 9/11/08.

Bark of a medium-sized tree. The bark is smooth like A. julibrissin, though this hybrid tree possibly is backcrossed with A. julibrissin.

Durham, NC 9/11/08.