Some things take more time to become plant accessible, some less.

I've not found any form of plant that doesn't break down into goodness eventually.

Leaves & young stems break down the quickest. There are some hardwoods that take decades to break down.

I'm waiting on some Tithonia Diversifolia cuttings. They call it tropical comfrey & it's biomass is apparently on par with chicken manure.

Greens and browns. All you need.