Foaming trees mystery

When Oxley Highway resident, Lucy Staughton, set out for the school bus run after recent rainfall, what she didn’t expect to see was foaming trees.

Mrs Staughton said after two-and-a-half months without rain it was a delight to see a heavy cloudburst come across the family farm, located between Gunnedah and Carroll in late February.

The tree lined driveway’s “strange behaviour” following the rain, surprised Mrs Staughton, who had “never seen anything like it”.

“I was quite surprised to see the foam running out of the trees,” she said.

“Because it was coming out of every tree, I thought it had to be a natural occurence, but it looked like a practical joke with lots of detergent.”

The foaming trees had Mrs Staughton intrigued.

“I initially thought having been through such a dry period, the eucalypts had a sort of protective coating on their leaves to minimise unneccessary transpiration of moisture,” Mrs Staughton said.

But the truth turned out to be even more remarkable she said.

Eucalyptus bark and leaves contain glycosylated alkaloids or isoprenoids called saponins, which foam when wet, they don’t emerge from the tree but simply wash off the leaves and bark.

Many terrestrial Orchids live at the base of Eucalypt trees precisely because of the “wetting agent” function of the Saponins released from the bark of those trees.

“I had no idea eucalypts had this amazing ability to improve water holding of the soil around themselves.”

Mrs Staughton said she was lucky to have seen and photograph the occurence as the storm passed as quickly as it arrived.

“By the time I returned home from the bus run, most of the foam was gone,” she said.