Acacia

( ak - KAY - shuh )

At-A-Glance Information

Acacia trees, commonly called Wattles, are native to tropics and other warm regions, mostly in Mexico and Australia. Many species are relatively short-lived (20-30 years) and can produce fragrant yellow flowers in early to midwinter. Foliage is typically grey-green to green and ferny. They can reach about 20 feet tall and are truly in their element when grown on hillsides and banks, though some species do well beachside. Most species are evergreen, and can be used as shade trees, background or screening plants, or simply as specimens. They can take the form of trees, shrubs, or groundcovers. Take care when planting Acacia trees in the garden, as some species have been found to have pods, leaves, and seeds that are toxic. This genus also contains some of the world's most invasive trees and shrubs, which spread aggressively in native landscapes. Check with local authorities before planting.

Acacia Species and Varietals

The genus Acacia includes 1,084 species, and is a member of the plant family Fabaceae. The genus name is Neo-Latin, and was pulled from the Greek word 'akakia', a term used to describe a preparation extracted from the leaves and seed pods. It was first formally described by Philip Miller in his publication The Gardener's Dictionary (1754). Acacia growing zones vary by species; for more information, see the descriptions below. To find your zone, click here: Zone Map.

Acacia aneura (Mulga, Mulga Acacia)
This species grows best in Sunset zones 8, 9 and 12-24 or USDA growing zones 8-11. Native to Australia, these small trees or large shrubs can reach 15-20 feet tall and wide, with thornless branches and gray-green to silver leaves. Yellow puffball flowers appear in winter and spring in the plant's native regions. Great for desert landscaping and xeriscaping.

Acacia baileyana (Bailey Acacia, Fernleaf Acacia, Cootamundra Wattle, Purple-Leaf Acacia)
Grown in USDA hardiness zones 8-11 and Sunset zones 8, 9 and 13-24. The species is native to Australia, and is widely planted due to its hardiness. These shrubby trees spread to 20-30 feet tall and 20-40 feet wide. Leaves are fern-like and blue-grey. Bright yellow flowers bloom early to mid-winter in the plant's native range. Variety 'Purpurea' (Purple-Leaf Acacia) does not get as wide as the straight species and has purple-tinged new growth, creating a multicolored effect in the garden.

Acacia berlandieri (Senegalia berlandieri) (Guajillo, Texas Acacia, Berlandier Acacia)
This species grows well in USDA hardiness zones 8a-11 (Sunset zones 10-24) and is heat tolerant. Native to Mexico, these plants have a shrubby growth habit to 5-12 feet tall and 5-20 feet wide. Leaves are feathery and bright green and branches are thornless. White, fragrant flowers bloom in clusters in early spring. Useful for screening, but can also be trained into a tree.

Acacia boormanii (Snowy River Wattle)
These trees grow best in Sunset zones 8, 9 and 12-24 (USDA growing zones 8-11). These shrubs are native to Eastern Australia and reach 10-15 feet tall and 6-15 feet wide. Gray green foliage contrasts well against fragrant, bright yellow flowers that bloom in puffs at branch tips in late winter to early spring. Spreads by suckers, making it great for hillside planting, erosion control or wind screening. Tolerates winter wet well, but does still appreciate fast-draining soil.

Acacia chinchillensis (Chinchilla Wattle)
This species grows best in Sunset zones 8, 9, 13-17 and 19-24 and USDA hardiness zones 9a-11b. Native to eastern Australia (Queensland), these plants exhibit shrubby growth to 3-6 feet tall and just as wide at maturity. Feathery, gray green leaves stand out against bright yellow ball-shaped flowers in late winter to early spring. Great for large container planting.

Acacia cognata (Acacia subporosa linearis) (Bower Wattle, River Wattle, Emerald Cascade Acacia)
Grows in USDA zones 8b-11 and Sunset zones 16-24, quickly forming a graceful tree with weeping branches 15-25 feet tall and wide. They can put on between 13 and 24 inches of growth each year in favorable conditions. Leaves are bright green and flowers appear in puffs of creamy yellow in spring. This species is sensitive to temperatures under 20 degrees Fahrenheit. Compact varieties include 'Limelight' (with lime green foliage) and 'Mini Cog'/'Cousin Itt' (a popular groundcover cultivar). Both of these compact varieties are good for containers and growing in mixed beds and borders.

Acacia constricta (Whitethorn Acacia, Mescat Acacia)
This species does well in USDA growing zones 7-11 and in Sunset zones 8-24. It is native to Texas, Arizona and Mexico, and is hardy down to -10 degrees Fahrenheit. It exhibits an open growth habit to 10-20 feet tall and just as wide when mature. Green leaves are smaller than other species' and fragrant yellow puffball flowers bloom in late spring and early summer. Decorative red seedpods follow. Great for desert texture or as a wildlife barrier plant due to its sharp spines.

Acacia covenyi (Blue Bush)
Native to eastern Australia, this species grows best in Suneset zones 8, 9 and 12-24 or USDA growing zones 8-11. It grows quickly into either a shrub or small tree depending on pruning. At maturity, these plants reach 12-20 feet tall and 10-15 feet wide, sporting brown branches and blue-gray leaves. Flowers are fragrant, yellow, and bloom profusely in winter and early springtime. Good as a windbreak or privacy screening plant.

Acacia craspedocarpa (Leatherleaf Acacia, Leather Leaf Acacia)
Native to Australia, this plant grows best in Sunset zones 8, 9 and 12-24 (USDA zones 8-11). Hardy to 20 degrees Fahrenheit. It is a slow-grower for the species and reaches up to 5-10 feet tall and 3-8 feet wide at maturity. Leaves are copper when young and age to gray-green. Bright yellow blooms shaped like tiny bottlebrushes appear in spring, followed by seed pods. Very tolerant of drought, but can also take regular water if soil drains quickly.

Acacia cultriformis (Knifeleaf Acacia)
This species of Acacia grows best in Sunset zones 12-24 (USDA zones 9-11). Native to Australia, it is a multi-stemmed small tree that gets 10-15 feet tall. Silver-grey leaves and clusters of fragrant yellow flowers that bloom in early spring. Great as a barrier plant or a screen. Cut branches are attractive in flower arrangements, where their leaf arrangement can be admired from a close perspective.

Acacia dealbata (Acacia decurrens dealbata) (Silver Wattle, Mimosa)
This species of Acacia grows best in Sunset zones 8, 9 and 14-24 (USDA growing zones 7-10). Native to Australia, this species gets to 65-100 feet tall and wide (around 30-40 feet in gardens) relatively quickly, adding several feet to its height each year. Feathery grey leaves and ball-shaped bright yellow flowers bloom in late winter or early spring.

Acacia fimbriata (Brisbane Golden Wattle)
These small trees and shrubs grow well in Sunset zones 8, 9 and 12-24 (USDA zones 9-11) and are native to eastern Australia. Brisbane Golden Wattle reaches 15-20 feet tall and 8-15 feet wide quickly, adding a few feet of growth each year. Leaves are dark green, and bright yellow flowers bloom profusely in springtime. Great as screen or windbreak. Tolerates frost and wet winters well given fast-draining soil.

Acacia greggii (Senegalia greggii) (Catclaw Acacia, Catclaw, Wait-A-Minute Bush)
This species of Acacia grows best in USDA hardiness zones 7a-11a (Sunset zones 10-24). It forms a deciduous shrub or small tree and is native to California, Texas, and Mexico. Individual plants reach 15-25 feet tall and wide. Leaves are dark green; branches have hooked thorns. Flowers are a creamy yellow and appear in spring through fall. These make good barrier plants.

Acacia iteaphylla (Willow Wattle)
Native to south Australia, this is a graceful, weeping species that reaches 8-12 feet tall and 10-15 feet wide. It produces narrow willow-like gray-green leaves that are red-pink when new. Flowers are pale yellow and bloom late winter to early spring. This species is a great screen or windbreak, especially near coastlines. It is best in Sunset Zones 8, 9 and 12-24 or USDA hardiness zones 8-11.

Acacia longifolia (Sydney Golden Wattle)
This billowing shrub reaches up to 10-25 feet tall and 9-15 feet wide when mature. Fragrant, golden-yellow flowers appear in spikes along branches in winter and early springtime. Foliage is bright green. This species grows best in Sunset zones 8, 9 and 14-24 or USDA hardiness zones 8-11. This species is notably resistant to Oak Root Fungus.

Acacia merinthophora (Zigzag Wattle)
This species is native to Western Australia and does best in Sunset zones 13-17 and 19-24 (USDA zones 8-11b). It species has an open, weeping habit and can reach 8-12 feet tall wide when mature. Very narrow, grey-green leaves are held on zig-zag patterned branches and bright yellow flowers appear in winter or spring followed by slender seedpods.

Acacia pendula (Weeping Acacia, Weeping Myall)
This species grows best in Sunset zones 13-24 (USDA hardiness zones 9-11) and is native to Eastern Australia. It grows slowly to reach 25 feet tall and 15 feet wide at maturity (20 years old). Blue-grey leaves contrast well against small, pale yellow flowers that bloom in clusters in late winter to early spring. Overall, this tree has as a graceful habit that makes it ideal for cascading down a wall, as an espalier, or simply to add drama and movement to the landscape.

Acacia podalyrlifolia (Pearl Acacia)
This species grows best in USDA growing zones 9b-11 or Sunset zones 8, 9 and 13-24. It can reach 10-20 feet tall and about as wide in a relatively short amount of time. Leaves are grey, round, and satiny to the touch. Flowers are yellow and puffy, and bloom in winter or early spring. This species is great as a patio tree and provides great winter color. It needs to be heavily pruned after blooms expire to keep a compact shape and doesn't tolerate summer water well. These small trees or shrubs are short-lived, surviving for about 10-15 years before needing to be replaced.

Acacia pravissima (Ovens Wattle)
This species grows well in USDA hardiness zones 8-11 or Sunset zones 12-24 and is native to Eastern Australia. Gets 12-20 feet tall and wide, and has profuse, triangular greyish green leaves. In winter and spring, cream to bright yellow fragrant flowers bloom. This species is hardy and can take frost, heat, wind, pollution and ocean exposure in stride. Good urban tree.

Acacia redolens (Prostrate Acacia, Spreading Acacia)
This species does well in Sunset zones 8, 9 and 12-24 or USDA zones 8-11. Native to Eastern Australia, this 1-6 foot tall and up to 15 foot wide plant has leathery, grey-green leaves. Flowers appear ball-shaped and fluffy in spring. It is great when used as a groundcover for banks and large areas with poor soil conditions. Can tolerate drought and heat. Groundcover varieties 'Desert Carpet' (pictured) and 'Low Boy' are low-growing to 1-2 feet tall and 12-15 feet across.

Acacia rigens (Nealie, Nealia, Needle Wattle, Needle-Bush Wattle, Nilyah)
This species is native to most of Australia, and can reach 6-9 feet tall and wide. Thread-like leaves are silvery-grey and in winter, branches become laden with small bright yellow flowers. Not picky about soil conditions. Great when planted in front of a wall or fence, where it can show off its unique foliage and flowers. This species is best in USDA growing zones 9-11.

Acacia smalliii (Acacia minuta, Vachellia farnesiana, Mimosa Farnesiana) (Sweet Acacia, Huisache, Casha Tree, Needle Bush)
This species of Acacia is best in zones 8, 9 and 12-24 (USDA growing zones 8-11) and is hardy to 15-20 degrees Fahrenheit. Native to Mexico and Southwestern United States, these plants can get 10-35 feet tall and 15-25 feet wide and typically form a multitrunked small tree or large shrub. These are deciduous plants with sharp spines. Flowers are puffy, yellow, fragrant and bloom in spring.

Acacia spectabilis (Mudgee Wattle, Glory Wattle)
Native to eastern Australia, this plant grows best in Sunset zones 8, 9 and 13-24 (USDA zones 9a-11b). It is a fast grower to 12-15 feet tall and wide when mature. Bark is silvery-white. Leaves are fern-like, and flowers bloom in bright yellow clusters in late winter or early spring. Purple seed-pods follow. Can tolerate frost but needs well-draining soil. A great choice for smaller gardens.

Acacia stenophylla (Shoestring Acacia, Weeping Shoestring Acacia)
This species does best in Sunset zones 8, 9 and 12-24 (USDA growing zones 9-11). Native to Australia, this is a fast-growing tree that has an open, weeping habit. Grows to 30-40 feet tall and 20-30 feet wide at maturity. Narrow, pale green leaves droop off of branches. New bark is maroon, and cream-yellow ball-shaped flowers bloom in late winter or early spring. Great when planted in groves; provides filtered sun for under-plantings.

Acacia verticillata (Prickly Moses)
This species grows best in zones 14-24, and is native to southeastern Australia. Gets 6-15 feet tall and wide. Dark green leaves are needle-like and short. Mimics the look of a conifer until springtime rolls around, when pale yellow flowers bloom. Great as a low hedge in windy areas and near coastlines. If left unpruned, this plant develops into a multi-trunked twisting plant.

Acacia vestita (Hairy Wattle)
This species is native to southeastern Australia, and grows 12-20 feet tall and wide. Branches have a weeping habit and carry soft gray-green leaves. This is a beautiful plant in springtime, when it is covered with profuse yellow blooms. Can be used as a focal point in landscapes or as a low screen or windbreak. Tolerates extremes of both drought and flooding. Grows best in Sunset zones 13, 15-17 and 19-24 or USDA hardiness zones .

Caring for Acacia

Take care when planting Acacia trees in the garden, as some species have been found to have pods, leaves, and seeds that are toxic. This genus also contains some of the world's most invasive trees and shrubs, which spread aggressively in native landscapes. Check with local authorities before planting.

Plant your Ranunculus in a space in the landscape that receives full sun; ideally, they appreciate between 6 and 8 hours of sun each day for the best blooms. When these flowers are grown in less light, they will not flower as profusely. Ensure that soil is well-draining and has a pH of between 6.0 and 7.5 (slightly acidic to neutral). Recommended soil pH varies depending on the species; for example Acacia gillii can tolerate highly alkaline soils, and Acacia gilbertii and Acacia strigulosa prefer slightly acidic conditions. If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost and sand before installing an Acacia. Apply a thin layer of organic mulch or stones at the base of trees and shrubs to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water new plantings regularly as they establish a strong root system in their new home. At maturity, Wattles are considered to be quite drought-tolerant, able to get by for most of the year if not the full year on rainwater alone. For a faster growth rate, water consistently during the dry months of the year. Ensure that soil is very well-draining, as these trees do not like to have their roots in standing water.

Some Acacia species will need to be staked or supported when they are young in order to help them establish a strong main trunk. Prune to maintain shape and size. Remove dead, dying, or diseased branches as needed, and remove inner growth to open up the canopy. Pruning is best done in the early springtime, before new growth pushes out for the year. If a rejuvenation pruning is needed, most species will bounce back from being cut back to about three feet from the ground. This will encourage shoots to form from the base and will create a bushier plant. Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. These plants are not heavy feeders, and this should be sufficient to provide the necessary nutrients for the active growing and flowering seasons. The natural habitat of these trees is warm, so they can take a lot of heat, but will struggle in cooler winter temperatures. Most species are not frost tolerant and will need some protection; make sure to have frost cloth on hand to throw over these trees (especially when they are young) during the cooler months of the year.

Growing Acacia in Containers
Acacias, especially dwarf or compact varieties, can do well when planted in large containers. Choose a pot that is at least 16 to 20 inches wide and deep, ensuring that it is about 2 inches wider than the original nursery pot. Fill the pot with a very fast-draining soil; it is a good idea to amend regular potting soil with perlite and sand to improve drainage. Acacias grown in containers will need more water than those grown in the ground; as a general rule of thumb, water whenever the top 2-3 inches of substrate feels dry to the touch. These plants will need to be potted up every two years to allow room for the root ball to expand.

Propagation

Acacia can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your tree, follow the instructions below:

Propagating Acacia by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
In late summer or early fall, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more semi-hardwood 2-6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth on your propagation, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub. Do not allow the Acacia to stay in a small pot for too long, as their root systems need a good amount of horizontal space and depth to grow correctly.

Propagating Acacia by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
Harvest your seeds. The seed pods on Acacia trees are pretty easy to spot, they're large and dangle from the branches, left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will begin to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
Place your seeds in a bowl and pour boiling water over them for scarification. This will get rid of the hard coating on the seeds, allowing them to germinate and grow. Leave the seeds in the water for 24 hours, and then lay them out to dry. Your seeds are now ready to be planted.
Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 10-20 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, as it grows. Keep it in an area with bright light and temperatures between 65 and 75 degrees Fahrenheit. Continue to care for the Acacia seedling until the following spring (after the danger of frost has passed), when you can transplant it to its new home out in the landscape.

Acacia seeds are held in pods that dangle from the branches of the tree once flowers have faded.

Acacia seeds vary a bit in color depending on the species.

Problems and Pests

This genus contains some of the world's most invasive trees and shrubs, which spread aggressively in native landscapes. Check with local authorities before planting. Acacia trees and shrubs are known for having issues with the following pests and diseases in the landscape: