Has it been very cold in Essex, Catty? In very cold weather we sometimes find ice crystals extruded from rotten wood and leaves etc, forming what we call 'ice flowers' although I think that there is a more correct name for them.

Hmm, couple of possible explanations - its been very, very wet, and sometimes in those conditions, excessive amounts of sap are present in the tree, and it may well ooze out in weaker areas. At this time of year though, you wouldn't normally expect the sap to be up as its the dormant period, but with this weather we're having, who knows. If it is sap related, it wouldn't have had any nasty smell about it.

The other possibility is a slime flux infection, but that usually is a bit smelly, though maybe not noticeably so at this time of year.

I'd just add to Bulbaholic - no, this end of the country has certainly not been very cold, and even though Essex probably gets colder than W. London, it's not been anywhere near cold enough for this to be ice/cold related.

thank you both, I have never seen anything like it before. It has been very wet but not icy down here.

It's called stemflow, slime flux or wetwood and it's a common disease among deciduous trees caused by bacteria. The bacteria grows inside the tree due to damage of the wood and carbon dioxide gas is released as it ferments.

The gas increases the pressure in the tree and forces sap to the outside of the tree trunk. This is called fluxing and results in large, dark regions on the trunk when the flux comes into contact with air and causes the bubbles that you saw. It becomes a breeding ground for other microorganisms as alcohols are produced and bubbles or foam form and it stinks.

Usually you will see insects around it because they will feed on this because this alcohol mixture attracts many bees, beetles and other larva to it.

wow! thank you Myron, you have a vast knowledge!

Whoa! Drunk Bee's & Beetles LOL, bet there sober now being May LOL.