The Mimosa: Arboriculture's Meryl Streep
Like great actors, some trees have the ability to set a mood in a garden and give it a cultural reference. What Northwesterners call the Mimosa or Silk Tree (Albizia julibrissin) is to arboriculture what Meryl Streep is to cinema.
Native to Asia from Iran to Japan, the tree can reach 40 feet, but more often tops out at about 20 in our climate. However, the canopy can spread twice its height, usually held aloft by three, sometimes five, trunks that veer out at an angle. The branches are filled with fern-like compound leaves. Seeing this tree from a distance, one is reminded of the African Savannah. You can almost see giraffes nibbling on the foliage. Up close and under the plant, you feel sheltered by dappled light, deep in a tropical rainforest. When the numerous, dense puffs of bloom open in summer, most often in rich pink and cream, you’re in New Orleans for Mardi Gras. Or perhaps you’re viewing a Chinese mural, hence the common name Silk Tree. When the branches sway gently and the leaves rustle, you may hear the haunting plunk of a geisha’s koto or see the lights fading on the final scene of kabuki. Then in winter, when the branches are naked, exposing the plants exquisite form, gardeners who have taken to wrapping the limbs in tiny white lights welcome you into a yuletide fantasy reminding us all that there is, indeed, peace on earth, good will toward mankind. Season by season, depending on your point of view, Albizia julibrissin is all of these things and more.
As climate change has brought milder winters and hotter, drier summers to the Pacific Northwest, this tree, which was once considered marginally hardy, has proven to thrive here. But to grow it to its best advantage it requires space to stretch and show off its form without competition from other plants. It needs to be in a spot that gets full sun. Once established it will thrive on only the irrigation that nature provides, but it is imperative that the tree be planted where drainage is perfect. Let it spend the winter in soggy soil and this tree will die in a few years or less.
Set Mimosa or Silk Tree in the ground from one-gallon to five-gallon cans. If you want to assure the handsome multi-stemmed growth pattern, you could even get three single-trunked plants and cluster them together, angling them out as you want them to grow. In time you’ll have a magnificent umbrella for a patio or a delightful pattern to look down on from a second or third story. As the tree grows, allow the new, top growth to guide the tree up, but prune off side growth and rub off buds that emerge along the trunk.
September is a good time to add a Mimosa to your garden. Water it well, but only until temperatures cool in late autumn. But if not this month, wait until early spring to put one of these trees in the ground. Like all things that require nurturing, from children to gardens, results will be better and your rewards greater with vigilance. Then the day arrives when you look at, or up and through, or even down on, this amazing tree, in its full splendor. It will speak to you, “Shall I take you to Japan, or Nairobi, Brazil or Mardi Gras…. and if you’re a giraffe, you are most welcome to munch on a few of my leaves.”
STEVE LORTON is a former editor of Sunset magazine.