Black Wattle (Acacia mearnsii) Australian Native Guide

What is Black Wattle?

Black wattle is a variety of wattle endemic to its native habitat in southeast Australia. It is part of the Acacia genus. Acacia mearnsii produces easily identifiable creamy white flowers at the ends of its branches in late winter. 

Its foliage is similar to mimosa, with palm-like fronds holding delicately divided, symmetrical, evergreen leaves that add structure and drama to any garden.

The edible seeds of Acacia mearnsii, or black wattle, are harvested when the seed pods turn brown and begin to open in late spring or early summer. They have a wonderfully nutty flavour with hints of chocolate and coffee when roasted.

See our in depth guide to growing Acacia including the best varieties to grow in Australia. 

Natural Habitat of Acacia mearnsii

Black wattle grows best in an exposed position, in full sun, and makes a great wind barrier for suburban gardens. They are drought tolerant but will need extra water and a light mulch if you intend to harvest the seeds every year.

How to Grow Black Wattle Tree

Black wattles are short-lived trees, typically reaching their full height of around 10m in under ten years. With proper care, they can live for around thirty years in cultivation but will need regular pruning and support as their limbs grow brittle with age.

Best Conditions to Planting Black Wattle

The best way to plant black wattle is to buy a young tree from a local nursery or online. Check that the roots are healthy, and not curling around the pot. If they are, tease them out gently to encourage outward growth.

Then plant black wattle in a hole twice the size of the container, and make sure the soil is well drained.

Light & Temperature

Black wattle grows well in any part of Australia and can cope with droughts just as well as brief frost spells. However, young trees should be planted with protection, and if frosts are predicated, it’s wise to add a thin layer of mulch to maintain the soil temperature, at least for the first couple of years.

Choose a bright, sunny location that gets at least 6 hours of full sun each day, as this helps black wattle seeds to ripen sooner after flowering.

Here is our list of different types of mulch and including their pros and cons. 

Soil & Moisture

Black wattle needs good drainage. If you have clay soil, consider growing black wattle in a container, or a raised bed. If that’s not an option, dig plenty of grit or sand through the soil before planting.

After planting, water black wattle trees generously to create good root contact, and then water them once a week for their first summer while their roots are getting used to more open space and drier conditions.

Exposure

Black wattle is happiest when exposed to the elements, with high winds generally seen as a positive. As such, black wattle makes great screening, even in coastal gardens.

Caring for Black Wattle Tree

Pruning Late Black Wattle

Black wattle does not need pruning but can be trained into a smaller shrub by cutting back half the branches each year, leaving the newest branches in place.

This will eventually create a shrubby form, and prevent it from getting too tall in small gardens.

Mulching & Feeding Black Wattle

Black wattle doesn’t need much in the way of nutrients but will produce healthier flowers, and more abundant fruit with high potassium, and high phosphorus feed.

As young plants develop, nitrogen mulches or granular fertilisers will help them grow, but after the first few years, you should focus more on seed production.

A generous mulch of garden compost, once every three years, is more than enough but can promote moisture retention unnecessarily, so use granular fertilisers and liquid feeds where possible.

Repotting Black Wattle Tree

If you notice that your black wattle has developed yellow leaves, it might be time to re-pot it. For black wattle in the ground, this isn’t an issue, but container-grown black wattle quickly exhausts their nutrients, and roots will begin to wrap around themselves, causing nutrient deficiencies.

Simply remove black wattle trees from their pots, tease their roots gently to encourage new growth, and plant them into fresh, gritty compost in a bigger container.

Ways to Propagate Black Wattle Tree

Propagating black wattle from seed and cuttings is straightforward, and far easier than many guides suggest. Avoid propagating in darkness, which will speed things up, but produce weaker plants that take longer to truly establish.

Propagating Black Wattle from Seeds

To propagate black wattle seed, you will need to use fresh seed, or soak dried seed for up to 24 hours to revive it.

• After soaking, or podding your wattleseed, mix compost and perlite in equal measure in small, 8cm pots. 
• Sow two seeds on the surface of each pot, and cover lightly with perlite to exclude some light. 
• Water each pot until the compost is evenly moist.
• Leave pots in a sunny position for up to a month, misting, or watering gently when the soil starts to dry.
• After germination, remove the weakest seedling and continue watering the strongest seedling.
• After a couple of months, your seedling will have healthy roots. Move it to a bigger pot, filled with a similar mix of compost and perlite for drainage.
• Plant in the garden when your black wattle is 2-3ft tall and has clearly defined foliage.

Black Wattle Propagation from Cuttings

Black wattle is not naturally predisposed for cuttings, but can easily be encouraged with the right tools, and method.

You will need:

• Small pots
• Perlite
• Garden soil or spent compost
• Rooting gel
• Sharp secateurs - see our product review of the best secateurs available online. 

Greenwood, or softwood cuttings are the most effective part of the plant for rooting, so choose new, non-flowering stems from this season’s growth just after the rest of the plant has finished flowering (flowering stems will not root properly).

• Cut just below a node (where a leaf meets a branch) roughly 15cm from a shoot tip. 
• Remove all but the top-most leaves, and dip the cut end in rooting hormone. (Find out the different types of rooting hormones here.) 
• Gently push your cutting into a pot filled with an even mix of perlite and garden soil or spent compost (the lower the nutrient levels, the better).
• Place your cutting somewhere warm and bright, but out of direct light. By the end of summer, it should have begun to root. Test by gently pulling each cutting. If there is resistance, then there are roots. 

How to Harvest Black Wattle

A few weeks after flowers have dropped, you should see green, pea-like pods, starting to develop. Over the next few weeks, those pods will swell as seeds grow inside them. By early summer they will begin to turn brown.

When the first dry wattleseed pods begin to open, it’s time to harvest. Grab a bag, bucket or basket, and start pulling the pods, one by one, from the tree.

Finally, open up the pods, remove the seeds, then leave them to dry on a windowsill, or drying rack, or roast them slowly in the oven.

For more information on how to use wattleseed, check out our guide to preparing and using wattleseed.

Black Wattle Pests and Diseases to Look Out For

Like most Acacia species, black wattle is native to Australia and well adapted to cope with our climate, making it a great low-maintenance tree that doesn’t suffer from common pests or diseases.

Blackfly and aphids can damage young growing tips in early spring, so keep an eye out, and simply wash them off with a hose. Black spots on the leaves may develop as a side effect of aphids and blackfly, caused by a fungus called anthracnose. Simply remove spotted foliage to prevent the spread of infection.

Black Wattle Frequently Asked Questions

Is black wattle invasive?

Black wattle is a native species across south-eastern Australia, and therefore not considered invasive. However, due to its rapid growth, and mass seed production, it can take over gardens, so should be managed appropriately, and planted more than 10m from buildings.

What can you use black wattle for?

The timber from black wattle is an effective firewood and can be coppiced for log burners and fire pits. The seeds are edible, with a lightly spiced coffee flavour, and are commonly used in baking.

Do ticks live in wattle trees?

The Wattle tick scale is a scale insect, rather than a tick, and is more common in rural settings. If you notice tick-like insects under the bark of wattle trees or gather around the base of leaves, they are not harmful to humans but should be removed to prevent damage to the plant.

Are wattle trees good for new build properties?

Wattle trees are beneficial for any garden where the soil has been compacted, disturbed, or otherwise harmed. Their roots are fast-growing, and the trees are relatively short-lived, so work well to create structure quickly, while helping to regenerate the soil structure beneath them.