Charlie called me this morning.
"Matt. Peat Moss? Mulch? What is the difference?"
Mulch can really be any organic or mineral material used to cover bare soil. Gravel, pine needles, cocoa shells - peat moss itself can be a mulch if it is spread accross the top of the soil.
I believe if you went into a garden center today in the spring of 2016 and asked for a quantity of "mulch," it would be understood as you were really asking for "shredded hardwood bark" - although cypress and redwood bark mulch are often available in bags these would not be the default mulch setting.
Peat Moss is a material harvested from peat bogs far far away. It is very decomposed organic matter that has collected in ecological and geological deposits over many earth ages. It is considered highly unsustainable by many as (1) peat bogs are very rich and delicate ecosytems in limited quantity on the planet and to strip the bogs for the benifit of our flower beds is frowned upon. (2) Peat Moss is also most often compressed into bags and trucked long distances to our gardens. Where it is being predominantly harvested now, I'm unsure, but back in the early eighties most peat available in WNYwas sourced out of Quebec. You may see bags of "Tourbe de Sphagnum."
Peat moss was the most common mulch used when I was a kid back in the late seventies and eighties. There is a whole series of techniques that go along with its use as a mulch which I get to show off once a year when I get a bag of peat moss for something that seem to confound everyone that works with me. I think peat moss bags are the only packaging that is opened by cutting the bag accross the middle and dividing the bag into two parts for use.
(If at anytime you wanna check and see if your horticulturist or landscaper professional is "old-school legit," put a 4.8 cubic foot bag of compressed Tourbe de Sphagnum in front of them and see how they work it. If they open it at an end... Take their certification card immediatly and burn it.)
Shredded hardwood bark I believe works better as a mulch than peat. Bark mulch suppresses weeds better. Way better. Bark mulch I believe creates a biological rhizosphere (like, an atmosphere for plants) more conducive to fungal populations desired by ornamental plants. Shredded hardwood is also (generally) a local product. There are many making hardwood mulch products locally - Buffalo Horticulture's most recent load came out of Rochester.
Peat Moss is most beneficial as a soil amendment. It is a standard ingredient in potting soils and professional growing mediums. Added to planting beds or site soils it helps to structure soil - breaking up clays and binding sandy soils. For the most part, peat moss does what any oganic matter does - improves drainage as well as nutrient availability and retention. However, as it is so well decomposed, its benefits to the biology of a soil are limited. I think the ideal use of peat moss is probably limited to commercial growing media (potting soil on a large scale) because it is very lightweight which reduces the resourses demanded in shipping and production. In the home garden, basic composts are much more effective as well as easier on the debit card.
There you have it Charlie. I hope you enjoyed your day in the garden.
Landscape designer and Proprietor of Buffalo Horticulture