Callicoma - Black Wattle in flower in Southern Highlands

This plant is not native to Robertson, but it is native to the creek-lines close by.
It lives on the creeks of the sandstone plateaux immediately below Robertson. Think Belmore Falls, and Carrington Falls. However, it is easily grown on our rich red basalt soil.

Ball-shaped flowers heavy with pollen grains

I have several trees of this species which I grew from seedlings collected along the local creek lines, where, after floods, seedlings can be collected (with a clear conscience) from mats of moss and root matters which have been lifted from the rock bed of the creeks. With no contact with soil, these seedlings are destined to die. From such predicaments, I can easily justify collecting seedlings to transplant into my garden.

This I confess to having done, in an experiment. And it has worked.

The flowers come from tightly bunched inflorescences.

I have two such trees, probably about 10 years old now. Both are doing really well, but strangely, one flowers earlier than the other and one is more open in structure than the other.

the specific name comes from the serrated edges of the leaf.

This plant is known by the name of Black Wattle, but it is not a Wattle in any sense.
It gave its name to Black Wattle Bay, in Sydney, because of the early settlers finding it convenient as a building material "Wattle and daub". That is because it forms many thing narrow stems which can easily be bound together, and coated with mud, to form a reasonably secure form of housing.

The flower bear a superficial resemblance to "Wattles" (Acacias), but it is not at all closely related to those plants. It is in a genus of its own, within the Cunoniaceae (the same family as Coachwoods and NSW Christmas Bush).