Glossary for organization of this post:
Broadleaf woody species- any deciduous plant that has a woody stem: fruit trees, deciduous trees, shrubs (eg: blueberry), grapes, and most bramble berries.
Non-woody species- any plant that does not have a woody stem (eg: all annual vegetables)
Softwood species – any evergreen/conifer (eg: cedars, pines, hemlocks, etc.)
Use Softwood Mulches on Softwood Trees only
To understand why I never recommend buying boutique mulches including bagged, dumped or loaded from retail sources, a discussion on the decomposition of softwoods is required. Most commercial mulches are from cedar and hemlock trees, both softwoods. These woods breakdown in a process called “brown rot” releasing polyphenols and other compounds that inhibit broadleaf species while nourishing softwoods. So only use softwood mulches on softwood trees!
If you make your own mulches or get it from one of the sources I’ve listed and are worried about the presences of ground softwoods, rest assured that 20% inclusion will not damage deciduous species as it will still be a “white rot”. If majority of the trees in your area are broadleaf, you are fine sourcing mulch from the sources I listed in the linked post.
Use woody broadleaf mulch on all species
Broadleaf mulches undergo a process called “white rot” that produces fulvic and humic acids that nourish just about all species of plants. Remember the ideal mulch comes from young wood on trees as well as all the other benefits that were discussed yesterday. Laying down a thick layer of broadleaf mulch on any soil, even well established turf, will yield excellent soil for cultivating plants they next year.
Coarsely ground, even unshredded mulches are ideal for the fungal activity that builds soils. Don’t mind the unshredded limb ends and larger chunks of wood in the mulch!
Grass-based mulches for Non-woody species
Hay, straw, dried grass clippings, etc. have a similar C:N ratio as woody broadleaf mulch but lack much of the humus building compounds found in young wood growth. They can still be used for water retaining characteristics for the annual plants when woody mulch is unavailable. Additionally, they will contribute organic matter as they rot as well as trace nutrients with larger relative proportions of potassium to the soils.
In between exceptions
As noted in the previous sentence, dried grass products can be worked into majority wood-based mulches for fruiting perennials to replenish the significant amounts of potassium that is removed in the annual fruit harvest.
Hardwood mulch from the small limbs in the tops of broadleaf trees is the mulch of most utility for all plants. If only softwood mulches are available even after checking all the places I recommend to get free mulch, let them rot for a year or two before use on broadleaf plants. Basically, treat softwood mulches like raw manure!
One additional type of mulch is worth noting in tomorrow’s post. I know, I know, this is such a riveting subject and I apologize for making you wait!