For a few weeks questions have been being asked about what appears to be a large stain across the escarpment to both sides of Mt Keira, with some concern trees may be diseased.

But just as the Christmas bush comes into flower at this time of year, the coachwood trees are making their presence known to those down closer to sea level.

Marcus Burgess, who runs the fascinating Dapto History in Pictures Facebook page, has explained the phenomenon is nothing but the seasonal bloom of a large rainforest tree. 

“If you look to the escarpment at the moment you will notice the lighter coloured patches of trees in scattered clumps here and there,” he wrote.

“These are the white flowers of Coachwood (Ceratopetalum apetalum) a large native rainforest tree.

“Just like its close relative the NSW Christmas bush (Ceratopetalum gummiferum) the flowers will change colour in the next few weeks to a vivid dark red.”

Mr Burgess said the coachwood tree has shown itself to be a useful timber in centuries past – and its utility is one that gave it its name.

“Coachwood timber is light and durable and was used in the construction of stage coaches and in WW2 the timber was sought after for its use in making lightweight gun stocks,” he said.

“This tree is an indicator species for the presence of warm temperate rainforest on the Illawarra escarpment and typically grows in association with aassafrass (Doryphora sassfrass) and lilly pilly (Syzygium smithii), the latter also flowering heavily at the moment.”

For those fancying an easier kind of access for a close-up view, coachwood trees and NSW Christmas bush can also be seen flowering within Wollongong Botanic Garden.

They are in the Australian open forest and grasslands collection adjacent to the temple garden.