Hi Tony, and welcome to NGA!
I like mulching with big chunks of pine bark. (But I do seem to have some kind of a "bark fetish".)
- Coarse bark lasts for a few to several years (can plastic make the same claim?).
- As it breaks down, they enrich the soil with organics. Feeds the worms and soil fungi.
- Bark chunks keep soil cool and moist in summer, and warmer in the fall.
- Rain falls right through (screen out any bark fines and mix them into raised beds for aeration).
- You can brush or rake chips aside before sowing, and push them back after seedlings come up.
- No plasticizers. No uncured monomers. UV? Don't care. Not ugly like plastic film.
- Bark production doesn't consume petrochemicals or electrical energy.
If you save the bags the bark came in, you still get some heavy-gauge plastic film to mess around with. I line raised bed walls or corners with it to reduce evaporation of ground water in the bed.
Big wood chips would probably work almost as well as top-dress mulch, but don't turn wood shavings under (nitrogen deficit and too much wood-eating fungi get nasty with fine wood or sawdust turned under the soil).
With both bark and wood chips, coarse big chunks are your friends. Sawdust and bark fines are likely to absorb light rainfalls and let none get through to the soil. Or they mat down and slow oxygen exchange into the soil.
Bark fines can go right into soil, but sawdust should be composted first. (Bark breaks down slower than wood of the same size (suberin) and also bark ahs a little N (more than wood, anyway).
