Foaming trees

[MickyB]

Walking through Sherbrooke Forest yesterday on a lovey rainy morning I saw something I have never seen before - foaming trees. Not just one tree but hundreds of them. At first I thought it may have been a practical joke with detergent but the foam in some trees was approx 30m up the trunk. After doing some research last night I found this information:

This occurs when rain water dissolves chemicals from the treebark as it flows down the stem of the tree. This changes the surface tension of the water, so that when it drips down towards the base of the tree, air is introduced due to the turbulence of the water, and foam is formed because of the altered surface tension.

and this:

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.

I spend a lot of time in forests but I have never seen this occur. Perhaps it only happens after extended dry periods (or perhaps it often happens and I am not observant enough). Just wondering if anyone else has seen foaming trees?

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[Rlgm12]

I suppose the chemical you stated along with others explains the bubbling that occurs in streams and rivers.
I have seen this bubbling on trees occur but I was much younger and I can't remember where.
Nice find

[photohiker]

I walk past a Eucalypt tree not far from home and there is always suds at the base when it rains.

[RonK]

I recall that way back in my primary school days there was a tree (quite a big one) in the school yard which we called the soap tree.

When the curly empty seed pods were rubbed between the hands in water they produced a generous lather.

I think it was actually a species of wattle.

[MickyB]

I suppose the chemical you stated along with others explains the bubbling that occurs in streams and rivers.

When I was researching I did read it was a similar process.

I walk past a Eucalypt tree not far from home and there is always suds at the base when it rains.

So my theory it only happens after dry periods is not correct? Does the foam still appear after a couple of days of consistent rainfall?

I recall that way back in my primary school days there was a tree (quite a big one) in the school yard which we called the soap tree.
When the curly empty seed pods were rubbed between the hands in water they produced a generous lather.
I think it was actually a species of wattle.

Very interesting Ron. I have heard of people using the leaves of Wattle trees for soap but not the seed pods. I wonder if one is more effective than the other.

[photohiker]

I walk past a Eucalypt tree not far from home and there is always suds at the base when it rains.

So my theory it only happens after dry periods is not correct? Does the foam still appear after a couple of days of consistent rainfall?

This is SA. Not a lot of consistent rainfall here

I guess I don't look at the tree every wet day, but will keep an eye on it for you now.

[Amy]

Our trees on our property often foam, we are in tassie. I read somewhere that this foam acts as a wetting agent in the soil.
I guess there would be more foam after an extended dry period as the tree would have had time to release more of the chemical?

[Ms_Mudd]

I had always wondered about this. Well there you go.