Black wattle is a pioneer plant, its not an invasive plant for the fun of it.
It provides benefits.
They only last about 15 years
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Benefits of Black wattle
In tougher environments where it is windy, frosty or very sunny, black wattle can be planted as a quick-growing tree among which other slower-growing and more sensitive species can be planted.
The black wattle provides protection for these other tree species, and as it ages and starts to collapse (often at around 15 years) the other trees emerge and take over.
As for all acacias, black wattle is a nitrogen-fixing plant.
This means its
roots have bacteria that allow it to take nitrogen from the atmosphere and incorporate it into the plant’s structure, which also benefits the surrounding soil.
This can be a real advantage to those establishing a garden in poorer soils or heavy clays.
The black wattle can also provide excellent natural mulch both in large-scale revegetation projects and domestic gardens.
The mulch forms from the leaves and bark as they are shed, but also from the twigs and branches as the plant dies.
As for the Gum trees, do you mean Eucalypts