Tree of the Month for January: Winter-flowering Acacias

By David Gress

In January and February in Santa Barbara, the first trees to present amazing colored canopies are the acacias. Most notable of these are three species that seem to explode with bright yellow flowers: Bailey Acacia; Acacia Silver Wattle; and Wattle Green Acacia.

Of the dozens of other Acacia species in our region, these three species stand out as the earliest winter bloomers – and those with the most abundant flower arrangements. In addition to flowering beautifully, they are persistent and well adapted to our Mediterranean climate.

All three have similar, small (¼ inch), rounded yellow flowers that occur in clusters or panicles that grow at the ends of branches and contain 25 to 30 blooms. The flowers have a deliciously sweet scent, something like fresh cotton candy. Fair warning: some people develop hay fever allergic to bulky pollen drifting in the wind.

The most ornamental is Bailey Acacia, which has been a popular tree here since it was first introduced in 1903 by pioneer horticulturist Dr. Francesco Franceschi. In our area, it grows rapidly into a small-scale tree (20-30 feet tall and 20-35 feet wide) with a broad, rounded crown.

Its gracefully weeping branches are covered in silver-gray-blue foliage. The bipinnately compound leaves are composed of 2 to 6 pairs of pinnae each bearing 12 to 30 pairs of pinnae (3/16 inch long), which create a delicate fern-like appearance. After pollination, the flowers produce bean-like pods (2 to 4 inches long and ¼ to ½ inches wide). Its bark is light gray; smooth when young but furrows with age.

It grows naturally as a multi-trunked tree or large shrub. It can be trained as a single-trunked tree, good for planting as an individual specimen or in mass plantings for a display. It does best in full sun and will thrive in any type of soil, as long as it has good drainage. It’s fairly drought tolerant and cold hardy down to 20 degrees F. It can survive our normal rainfall but, naturally, does best with supplemental irrigation during the dry season.

Acacia Bailey is also known by other common names: ‘Fernleaf Acacia’; “Golden Mimosa”; and “Cootamundra Wattle”. Its botanical name is Acacia baileyana. The genus name, “Acacia“, is Latin but is derived from the Greek word “akakiameaning “Egyptian thorny acacia”. The specific epithet “baileyanahonors the Australian botanist, Frederick Mason Bailey (1827-1915).

It is native to a limited area in the Cootamundra region of New South Wales, Australia, where it is known as Cootamundra Wattle. The word “wattle” comes from an Old English word for branches and twigs that were used to weave trellises for sheep fencing and other structures. In Australia, early European settlers made huts and shelters from acacia trees, using the long, flexible branches of acacia trees mixed with mud. On this continent, the term has become synonymous with acacias and the name has stuck, well, like mud.

There is a cultivar with purple leaves, Acacia baileyana ‘Purpura’. Its leaves emerge with a distinctive lavender to almost purple color that turns silver gray with age. It is a shorter tree, with a maximum height of 20 feet.

The other two species, Silver Wattle Acacia and Green Wattle Acacia, are quite similar to each other, differing mainly in the color of their leaves. They both differ from Bailey Acacia in their taller upright growth habit (up to 50 feet tall with a 40 foot spread) and relatively larger leaves. Their compound bipinnate leaves have 20 to 50 pairs of pinnules on the rachis up to 4 inches long, with 10 to 26 pairs of pinnae. These species occur naturally in southeastern Australia, with Silver Wattle’s range extending further into Tasmania. They naturally hybridize together and also naturally hybridize with the Black Wattle (Acacia mearnsii), making their exact identification rather difficult.

The Silver Wattle, also known by the common names “Blue Wattle” and “Mimosa”, has the botanical name, Acacia dealbata. The specific epithet “dealbata“, comes from the Latin word “dealbatusmeaning “whitewashed”.

The Green Wattle has the botanical name, Acacia decurrens. The specific epithet “decurrensis derived from a combination of the Latin words, “de” and “curro”, meaning “flowing over the stems”. The Green Wattle also differs from the other two species in that it has dark gray bark that frequently develops warts along the trunk.

In Australia, acacia trees are used in many ways: for their timber – to make furniture, tools and fine carpentry; for their flowers – to make dyes, food additives and flower arrangements; and, for their sap – to formulate chemicals for medicine.

Unfortunately, these Acacias, like many other Acacias, are short-lived, with an expected lifespan of 30 to 40 years. Luckily, they are easy to grow and appear to be pest and disease free. They are known to be invasive in some Mediterranean regions; locally they don’t seem to be a noxious tree problem. As a precaution, planting should be restricted to developed urban landscapes. These trees are essentially maintenance free; however, periodic pruning to lighten the load on the branches is advised, as their wood is brittle and can break in winds and rain.

In the right place, any of these charming acacia trees will make a stunning addition to a residential, commercial or park landscape. Soon, their spectacular yellow flowers will be easy to spot around town!

Bailey acacias are seen on the 2200 block of Alameda Padre Serra, on the 1800 block of Eucalyptus Hill Road, at 1 S. Los Carneros Road, and on Highway 101 at the State Street/Highway 154 overpass, as well as scattered throughout the Mission Canyon area. Silver Wattle Acacias and Green Wattle Acacias can be seen on the Old Coast Highway (between Park Place and Hot Springs Road), the 100-200 blocks of Hot Springs Road (with Black Wattles), and the 600 block of Cold Spring Road .

Tree of the Month items are sponsored by Santa Barbara Beautiful, whose many missions include raising awareness and public appreciation of Santa Barbara’s many outstanding trees and, through a long-standing partnership with the City Parks & Recreation Department, funding and planting trees along City streets.

Those who wish to honor a special person can do so with a lovely memorial marker that will be installed at the base of an existing street tree in the city of Santa Barbara. Because Santa Barbara Beautiful has helped plant over 13,000 street trees to date, there are plenty of trees to choose from! Application forms are available on the Santa Barbara Beautiful website,

Article and photos by David Gress

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