Sweet Acacia, huisache

Vachellia farnesiana, Vachellia farnesiana var. farnesiana

sweet acacia blooming at Academy Village

About the Plant

In the Tucson area, the golden flowers of sweet acacia perfume the air in early spring, often as early as February. Sweet acacia is a variable species that can grow as a large shrub or a tree to about 30 feet. Nursery plants labeled as Vachellia farnesiana var. farnesiana (but may still be labeled as Acacia smallii) are reliably large and tree-form and are cold hardy in the Tucson Metro area. Plants labeled as Vachellia farnesiana (or Acacia farnesiana) are shorter and may be damaged in Tucson's coldest winters.

Grow sweet acacia in full sun and in deep soils with good drainage. Keep it away from strongly reflective surfaces. It can survive on natural rainfall once established. Sweet acacia may drop its leaves in dry weather or cold winters.

Sweet acacia is a short-lived plant with brittle wood. Large, overgrown plants may break in heavy winds. Pruning is difficult as new shoots sprout wherever pruning cuts were made (see photo above). For more information, see references below. There may be improved horticultural selections available. Ask at your local nursery.

Notes:

  • Previous scientific name for Vachellia farnesiana was Acacia farnesiana. Previous scientific  name for Vachellia farnesiana var. farnesiana was Acacia smallii.
  • Some scientists believe sweet acacia is native to Central America or South America. In Arizona it is listed as native to the Baboquivari Mountains  but it has spread and is found outside cultivation in Pima and Maricopa Counties. Sweet acacia has naturalized throughout the warm parts of the world and is considered a pest species in Australia, Hawaii, and other areas. The plant is not on the SEINet plant checklist for Saguaro National Park-Rincon Mountain District. Thus, it is considered a non-native plant on this website.
  • Allergy Alert: some people are allergic to the pollen of sweet acacia

Wildlife value: may attract insects

More Information

Weekly Plant on sweet acacia

Horticultural information from ASU (includes ethnobotanical information)

Information from Invasive Species Compendium

Map of distribution in the US (yellow is rare, blue-green is adventive)

Technical botanical description from SEINet

In books:

Native Plants for Southwestern Landscapes by Judy Mielke, page 49 (as Acacia farnesiana)

Trees and Shrubs for the Southwest by Mary Irish, page 92 (as Acacia farnesiana)

ID Characteristics

This plant is in the Fabaceae - the legume (pea and bean) family.
sweet acacia blooming at Academy Village
The more cold-hardy sweet acacia (Vachellia farnesiana var. farnesiana) is typically grown in the Tucson area. It can reach to 30 feet with an equal spread.
The older bark of sweet acacia tears off in strips. This is a good ID characteristic to distinguish this plant from native acacias, such as white-thorn and catclaw acacia.  Large white thorns, grouped in twos, may be present on the trunk.
The leaves are 1-4 inches long, alternate and bipinnately compound. There is only one complete leaf in the top photo above. Each leaf has 4-12 sections arranged opposite each other, each with 8-19 pairs of straight leaflets, each less than 1/4 inch long. There is a small, round gland near the base of the leaf stalk - green in the top photo, red in the second photo. There are two white stipular spines at the base of the leaf.
The golden flowers of sweet acacia are grouped in ball-like clusters about 1/2 inch wide. Their fragrance is strong and sweet.
Sweet acacia fruit is 1-3 inches long, initially green, then maturing to a dark brown. It may stay on the tree for many months. When the pods fall, however, they can create quite a mess. Unlike many legume fruit, these pods are rounded in cross-section, not flat. This is another good identification characteristic.