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Gardening 101: Acacia

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Gardening 101: Acacia

February 21, 2018

Acacias, Acacia: “Wattles”

As garden plants go, acacias are certainly not without their faults. These shrubs and trees are known for being short-lived, possessing dangerous thorns, attracting stinging ants, and spreading with heedless aggression. However, like some sort of botanical femme fatale, acacia seduces the unwary plant lover by adorning herself with truly spectacular displays of gorgeous and often highly perfumed flowers.

Read on for everything you need to know about how to grow and care for acacias.

Acacia aculeatissima, also known as thin-leaf wattle, is a low-growing shrub, shown flowering in early October in Australia. Photograph by DavidFrancis34 via Flickr.
Above: Acacia aculeatissima, also known as thin-leaf wattle, is a low-growing shrub, shown flowering in early October in Australia. Photograph by DavidFrancis34 via Flickr.

I still remember the showstopper I saw one day in front of a hideous bunker-like medical clinic in a desolate part of Texas just north of Big Bend National Park. Seemingly oblivious to her mundane and largely unpopulated surroundings, this tree appeared to be flaunting her beauty for her satisfaction alone. She was covered with bright yellow blooms visible in that flat arid country from miles away. Such arrogance. Such allure. I was in love. Only the fact that I lived in the Northeast instead of a warm climate saved me from acquiring an acacia straight away.

Acacia leprosa var. graveolens, known as a varnish wattle, has pale powder-puff flowers. Photograph by DavidFrancis34 via Flickr.
Above: Acacia leprosa var. graveolens, known as a varnish wattle, has pale powder-puff flowers. Photograph by DavidFrancis34 via Flickr.

Despite their faults, acacias can be remarkably easy to grow. They can thrive in almost any type of soil, are drought tolerant once established, and require very little ongoing maintenance. Hundreds of varieties of both deciduous and evergreen trees, shrubs, and ground covers ensure that you should be able to find one that will work in any mild-weather landscape.

Native to Australia and Tasmania, Acacia verticillata is a low-growing shrub that blooms in springtime in its native regions. Photograph by DavidFrancis34 via Flickr.
Above: Native to Australia and Tasmania, Acacia verticillata is a low-growing shrub that blooms in springtime in its native regions. Photograph by DavidFrancis34 via Flickr.

Cheat Sheet

  • As relatives of the pea family, acacias can fix nitrogen in the soil, which enhances fertility and stability.
  • Acacias are fast growers and lend themselves well to being trained as living fences and hedges, and low-growing varieties are useful as ground covers to prevent erosion.
  • If your variety has thorns, be sure to locate it safely away from high-traffic areas.
  • Acacias work well in xeriscapes and Mediterranean-style gardens.
Acacia paradoxa. Photograph by DavidFrancis34 via Flickr.
Above: Acacia paradoxa. Photograph by DavidFrancis34 via Flickr.

Keep It Alive

  • Water an acacia once a week until your plant gets established, then only in hot weather, every three to four weeks.
  • When you water, deeply soak the entire area under the canopy to avoid encouraging shallow roots.
  • Acacias need full sun and most are hardy in USDA zones 9 to 11.
  • Provide good drainage.
  • Prune lightly to remove damaged or dead branches.
Photograph by Chelsea Fuss.
Above: Photograph by Chelsea Fuss.

One thing to keep in mind when choosing an acacia is that confusion currently reigns over how these plants are classified. Part of the pea or legume family (Fabaceae), acacias were once officially part of a huge genus of similar plants that were native to tropical and subtropical regions. They frequently came from either Australia or Africa, although some also came from South America and Europe. In 2011 some acacias, mainly the Australian natives, were separated and allowed to keep the official Acacia genus classification. Their relatives from Africa and other places were placed in different genera. That has created some odd situations. For example, the plant known as sweet acacia, which is a small tree native to south Florida, now has the botanical name of Vachellia farnesiana.

Despite its common name, sweet acacia (Vachellia farnesiana) is no longer officially an acacia. Photograph by Forest and Kim Starr via Flickr.
Above: Despite its common name, sweet acacia (Vachellia farnesiana) is no longer officially an acacia. Photograph by Forest and Kim Starr via Flickr.
To make an easy floral arrangement with acacia, watch for our upcoming Rethinking Flowers post tomorrow. Photograph by Chelsea Fuss.
Above: To make an easy floral arrangement with acacia, watch for our upcoming Rethinking Flowers post tomorrow. Photograph by Chelsea Fuss.

Some acacias known for being good garden plants include acacia bailey (Acacia baileyana), a drought-tolerant, heat-loving tree that produces fragrant yellow flowers in the spring and can reach a height and width of 30 feet. Blue-leaf wattle (Acacia saligna) has distinctive willow-like foliage with phyllodes instead of leaves. Phyllodes are petioles (stalks that attach leaves to stems), which have evolved to perform the functions of leaves and are common to many acacias. Blue-leaf wattle typically grows to heights of 15 to 30 feet. Espinillo (Acacia caven) is a small tree or shrub that can tolerate freezing temperatures as low as 10 degrees Fahrenheit.

Acacia provincialis is a shrub or small tree and flowers in spring. Photograph by DavidFrancis34 via Flickr.
Above: Acacia provincialis is a shrub or small tree and flowers in spring. Photograph by DavidFrancis34 via Flickr.

In Australia, where these plants are known as “wattles,” there are nearly a thousand acacia species. The national floral emblem is the golden wattle (Acacia pycnantha) and Wattle Day is celebrated each year on September 1. The word “wattle” comes from the early use of acacia wood to make woven fences that resembled the wattle fences of Britain. Acacias continue to provide useful products: tannin from the bark, animal fodder from the seed pods and leaves, and gum arabic from the sap, which has innumerable uses in commercial production of candies, cosmetics, soft drinks, baked goods, and flavorings. Fine furniture and even boomerangs are made from acacia wood.

For more about how to grow and care for acacias, see Acacia: A Field Guide to Planting, Care & Design and find other spring-flowering shrubs and hedges in our curated guide to Shrubs 101. If you garden in a warm climate, see design inspiration and growing tips:

Finally, get more ideas on how to successfully plant, grow, and care for acacia with our Acacia: A Field Guide.

Additionally, get more ideas on how to plant, grow, and care for various ground cover plants with our Ground Covers: A Field Guide.

Finally, get more ideas on how to plant, grow, and care for various shrubs and hedges with our Shrubs: A Field Guide.

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