Apparently there’s a whole canal full of wattle, the wattle canal, huge battle was fought there in WWII.
I’d often wondered what wattle, of wattle and daub, was. Sometimes, rather than using mud, the “plaster” was made of dung, probably because so much was around all the time. They figured out how to treat it so there was no smell. That’s their story anyway.
Whatever the plaster, you would want something that does not easily absorb water after it dries. Otherwise your wall coating may just weaken and slide off.
A mud with high clay content would work. Horse dung (mixed with a bit of clay?) might work due to its high fiber content.
It seems as though this would be a rather high maintenance structural material needing to be replenished regularly much like a thatched roof.
It you really wanted it to last you add blood to the mix.