Bark and Compost are both mulches but mulch is not necessarily compost or bark. Mulching is a term that refers to covering the root base of plants to help retain moisture, fertilize and aid in preventing weeds. The variety of plant material along with your visual expectations should determine what type of mulch you use. Compost is a very fresh green mulch which is very high in nutrients. It is also actively decomposing and becomes soil very quickly. Once spread, 5 yards of compost quickly shrinks to 2.5 yards. That shrinkage has been eaten up by the plants growing in it. So your 2.5 ‘tall tomato plant is now 5’ tall. So, compost is great for vegetable and flower gardens.
Bark is the byproduct of woody plant material. If Compost is the greenery of the plants, Bark is the stems, trunks and branches of plants. Bark provides a cover for established shrubs and trees. It can be used as a low impact or temporary path or walkway. Bark eventually decomposes but at a much slower rate than compost.
There are many types of mulches which combine different materials. Sawdust, manures, sand and peat are some of the most common ingredients we find in mulch.