Also known as mimosa or wattle trees, acacias are usually evergreen trees and shrubs that provide year-round colour and interest to the garden.
Where Do Acacia Trees Grow?
Acacia trees are native to tropical and subtropical regions, such as Australia, Southern Africa and the Southwestern United States. However, some varieties grow well in other parts of the world, including the UK.
As you’d imagine, acacia species grow best in milder areas of the country, doing particularly well in the south of England, where they’re less likely to encounter harsh frosty temperatures. But given a sheltered spot in full sun, acacia trees are hardy enough to survive in most parts of the UK.
The Main Features of An Acacia Tree
Acacia Tree Flowers
Undoubtedly the main attraction, acacia trees are most often grown for their stunning golden yellow flowers. The bright yellow blooms are sweetly scented, attracting bees, butterflies and other pollinators to the garden. Acacia species usually flower in winter or spring, making them an important nectar source for early pollinators and bringing an outdoor space to life with an abundance of tiny, fuzzy, bright yellow flowers.
Acacia Tree Leaves
Acacia trees have easily-recognisable leaves comprising pairs of small leaflets (called pinnate leaves) with a soft, feathery, fern-like appearance. The foliage is usually bright or bluish-green and remains on most acacia species throughout the winter.
Acacia Tree Thorns
Many species of acacia trees have sharp thorns running along the branches. These tend to be found more on varieties non-native to Australia, while Australian species are usually thorn-free. The thorns on wattle trees can reach up to 3 inches long and often grow in pairs, protecting the foliage from being eaten by herbivores.
Acacia Tree Seeds
Acacia seeds grow inside brown pods hanging from the tree’s branches. The distinctive seed pods are around 7cm long, and the brown or glossy black seeds often shine through. Once the seeds are ripe, they are expelled from the pods, dropping to the ground where they can be collected or left as food for birds and small mammals.
Acacia Tree Wood
Acacia trees provide strong and durable hardwood with an attractive orange tone. Acacia wood is highly resistant to fungus, and its water-resistant properties ensure it won’t warp easily.
Acacia Tree Bark
The bark on acacia trees is deeply-furrowed and has a grey-to-brown hue. Acacia tree bark is high in tannins and is used in making leather, dyes and inks.
Types of Acacia Tree
There are over 1500 varieties of trees in the acacia genus. Read on for some of the more common and well-loved acacia tree species.
Silver Wattle (Acacia dealbata)
Probably the most common type of acacia tree grown in the UK, silver wattle or acacia dealbata, is also known as blue wattle. It grows to around 6m tall, and its yellow flowers bloom from late winter.
Sweet Acacia (Acacia farnesiana)
Sweet acacia is a large shrub or small tree with multiple trunks. The semi-evergreen foliage grows along criss-cross stems covered in spiky thorns. Highly scented sweet acacia flowers are long-lasting with a cloud-like appearance.
Black Wattle (Acacia concurrens)
Also known as green wattle, acacia concurrens is a perennial acacia tree native to southeastern Australia. Unlike many other species of acacia tree, black wattle doesn’t bloom until mid-summer, with the attractive flowers appearing from July until September.
Creeping Wattle (Acacia saligna)
Sometimes known as blue leaf wattle, acacia saligna can be grown as a large shrub or small tree with a short trunk and a weeping growth habit. It can reach up to 8m tall and flowers from late winter into early spring.
Flax-Leaf Wattle (Acacia linifolia)
This species of acacia is also known as white wattle due to its creamy white acacia flowers. This variety blooms in summer and sometimes produces a second flush of flowers in winter. It is native to southern Australia and can reach up to 5m tall.
Spreading Wattle (Acacia genistifolia)
Growing to around 3m tall, acacia genistifolia is a compact tree that spreads 2m wide. Spreading wattle is among the first to flower, with pale yellow blooms appearing as early as December though peak flowering time is late winter.
Blackwood Acacia (Acacia melanoxylon)
Acacia melanoxylon is an evergreen variety with a graceful habit. It is a medium-sized acacia tree that grows up to 12m tall. Blackwood acacia produces an attractive show of white to pale yellow blooms from early spring.
Box Leaf Wattle (Acacia buxifolia)
Box leaf wattle is a compact evergreen variety, reaching up to 4m tall. It is usually grown as a shrub and flowers between July and November. Acacia buxifolia boasts blue-green leaves resembling those of a buxus or box shrub – hence the name.
Sydney Golden Wattle (Acacia pycnantha)
Flowering in late winter and spring, golden wattle grows to around 8m tall. The tannin-rich, grey-brown bark is smooth on young trees but becomes more furrowed as the plant matures. Bright green pinnate leaves contrast beautifully with the brightness of the fluffy golden flowers.
Weeping Myall (Acacia pendula)
Considered one of the prettiest trees in the acacia family, weeping myall is a medium-sized tree with multiple trunks, weeping branches, and pale yellow flowers blooming in winter and spring. This variety makes an excellent feature tree for a front garden.
Hickory Wattle (Acacia implexa)
Hickory wattle is a moderately fast-growing species of acacia tree with an ultimate height of 5-12m. It flowers from December to April, and produces a fine show of pale, almost white blooms.
Cootamundra Wattle (Acacia baileyana)
Also known as bailey acacia, cootamundra wattle is usually grown as a large shrub, reaching up to 6m tall. Silvery pinnate leaves remain in place throughout the year, and the glorious yellow flower heads appear in winter and spring.
Spike Wattle (Acacia oxycedrus)
As you’d imagine from the name, spike wattle is a prickly shrub grown for its density and compact shape. Reaching up to 3m tall and 2m wide, this variety of acacia is ideal for sunny borders. Buttery yellow flowers appear from summer into late autumn.
Gum acacia (Acacia senegal)
Native to Sudan, gum acacia trees yield gum arabic, a product widely used in adhesives, inks and pharmaceuticals. It can reach 15-20m tall and is mainly found in dry desert regions.
Where to Grow Acacia Trees
Acacia trees flourish in well-draining sandy or loamy soil with a neutral to acidic pH. They prefer a bright sheltered spot to soak up the sun away from strong or chilly winds.
Acacia trees grow well in pots and containers. However, they will need to be moved indoors or into a greenhouse to survive the winter months.
Caring for Acacia Trees
Acacias are relatively low-maintenance flowering plants that don’t demand much attention to thrive.
Watering
Newly planted acacias need to be watered regularly to help them settle into their new spot. Once established, wattles are largely drought-resistant and only need to be watered during particularly dry spells of weather – though potted trees and shrubs need watering more often.
Pruning
As a general rule, acacia trees don’t need much pruning other than removing dead or damaged branches. However, they respond well to a gentle prune and can easily be maintained at the right size and shape for your garden.
Bear in mind that the flowers are formed the previous autumn, so don’t prune after late summer. Otherwise, you’ll cut away all those striking blooms.
