Have recently noticed strange growth on the underside of my flow hive roof. Have no idea what it is. Hoping someone can shed some light on what it may be…
Hi @Lovethehoney, definitely looks like a leaking roof.
Try undoing the end roof screws , run a small amount of “no more gaps” along the tops of the end panel, then screw the roof back down. wipe away any no more gaps inside the roof.
Another possibility is mildew, others on the forum may be able to advise how to get rid of mildew.
Cheers, G
Nice colour 
Have no idea what it is. If it were just staining I would say, gum leaching out of the wood, but seems a bit thick for that.