Home & Garden Columns

Green Neighbors: A Toast to the Handsome Blooming Mimosa

By Ron Sullivan
Tuesday July 24, 2007

The mimosas are blooming, and I’ll bring the orange juice if you’ll bring the champagne to toast them with that favorite brunch beverage—mimosas, of course. Looking at the current price of OJ, you might be getting a bargain.  

Mimosa, Albizia julibrissin, also gets called “silk tree” (not to be confused with the more tropical “silk-floss tree”) and “sensitive mimosa” when people confuse it with the Brazilian native Mimosa pudica, which is more a shrub than a tree, with somewhat similar leaves and more globular, uniformly pink flowers. Both species can show up as weeds in some parts of the country, especially the wetter Southeast. 

The shade of A. julibrissin flowers can vary widely, from gilded to outright rosy. They’re always engagingly fluffy and light-catching though, and attractive to bees and butterflies.  

I’ve seen hummingbirds investigating them, but I can’t say how much nutrition the birds actually get out of the flowers.  

I don’t believe they’re sticky and dangerous to local birds the way blue-gum eucalyptus flowers are, at least. Euc flowers have been blamed by observant and nonhysterical birders like Rich Stallcup for the deaths of warblers that he and others have found under the trees with their nostrils completely occluded by, um, gum gum.  

Birds that co-evolved with eucs in their native Australia have bills that are longer below the nostrils, so they can use the sweet flowers and any bugs garnishing them with no problem, but ours haven’t been around eucs long enough I guess. Eucs’ bloomtime in winter when we have more more hungry warblers around because they migrate here might be compounding the problem.  

Albizia species—there are some hundred-plus of them—hail from Africa, Asia, and Australia; the species we have here is from China by way of Italy, evidently, where Filippo degi Albizzia introduced the whole genus in 1749. Where it lost the second z is one of those things I’ve never quite caught up with.  

Looking at the long puckered seedpods, you might guess immediately that our mimosa’s a bean, a legume. Like many but not all legumes, this tree fixes nitrogen. What? What that means is that these plants have a set of symbiotic bacteria housed in nodules in their tissues, primarily in their roots (though Hawai’ian koa keeps some up in aerial crotches), that work some of the 78 percent of the air that is nitrogen into compounds the plants can use, much more efficiently than other soil bacteria that live on their own. 

Some legumes, our native redbud for example, don’t bother with this but similar process has evolved in other plant species, like some tropical grasses, and other bacteria species. Evidently it’s a good idea. You can certainly understand its usefulness in nutrient-lean tropical soils.  

Mimosas aren’t long-lived as trees go, and a root fungus that kills them has begun to show up in California. But they’re handsome, tough, and cast a nice lacy shade we can sit in to drink those other mimosas. 

I’d say plant them—away from wildlands, please—and enjoy them. Slainte! 




Photograph by Ron Sullivan. 

Mimosa flowers and foliage. This tree gets planted mostly in private yards and gardens, but the rosy individual shown here lives on a very public street in San Anselmo. 



Ron Sullivan is a former professional gardener and arborist. Her “Green Neighbors” column appears every other Tuesday in the Berkeley Daily Planet, alternating with Joe Eaton’s “Wild Neighbors” column. Her “Garden Variety” column appears every Friday in the Planet’s East Bay Home & Real Estate section.