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Thursday - August 07, 2008

From: Agoura, CA
Region: California
Topic: Non-Natives
Title: Pruning of non-native chocolate mimosa
Answered by: Barbara Medford

QUESTION:

I have a one year old chocolate mimosa that has grown 2.5 feet in height. It has seven leaf stems two feet from the bottom and only three at the top canopy. The trunk is only three quarters of an inch in diameter. There are five feet of trunk with no bud growth at all. Should I prune off the top down to the bottom where the growth is more abundant?

ANSWER:

What is commonly referred to as a mimosa or silk tree is a relatively small, fast growing tree. The mimosa tree is a native of southern and eastern Asia and the burgundy-leaved cultivar "Summer Chocolate" was recently developed in Japan. Since it is non-native to North America, it will not be in our Native Plant Database, so we will go hunting for other information.

So, we'll just talk about mimosas, in general, because the culture of the "Summer Chocolate" seems to be no different from that of other mimosas. It has a beautiful burgundy leaf, turning that color after a green spring. The mimosa often, but not always, develops multiple trunks. If we understand your description correctly, you have a clump of growth near the ground and a clump of growth at the top, with a lot of empty space on the trunk in between. In the first place, now is not a good time to prune anything, You should wait until late Fall, when it's cooler. In the second place, this is a very young tree to be expecting any shape to form. Ideally, you want a "leader" trunk on your mimosa, from which the smaller branches grow, instead of the multiple trunk with a possible weak "v" in the trunk. Our advice is to take care of the little tree, making sure it has plenty of water, and see what the shape is looking like in mid-winter. Hopefully, there will be more growth, more green branches on the upper part of the trunk, and you can prune the lower branches to help establish a trunk.