Dr Bob would know but I seem to remember that bark from conifers is best as some bark from deciuous trees can develop coral spot that can affect the trees and shrubs -- hope someone can confirm or deny this-- I think that any composted bark should be OK

Similar answer to one I gave yesterday, spread it out on a poly sheet, water over with a fine rose in a solution of Armillatox, 30mls to 5litres of water, cover and leave for two weeks, uncover and spread on your mulch when the smell has gone. Do not use round edible plants.

Thanks Dr B :o)