all commercial mulches are loaded with persistent herbicides

I lost a couple years of tomatoes to persistent herbicides in what was supposed to be good compost... lesson learned! These days I've got a nice equilibrium with the chickens making the compost for me, though.

While the thread title may be a bit over the top, the problem is very real. Some years ago a family member had his pond contaminated and his garden soil destroyed.

I think it's a lot worse in the U.S.A. but it's coming here. Some of the same nasties are now marketed north of the 49th.

Several years ago the electic utility said "hey there are some listed weeds on the right of way, and we'd like to spread xxx at no cost to you." Most people would automatically say "okay, sure." When I asked what they were spreading it was clearly a persistent chem, in a sandy soil, and might migrate to my neighbours' ponds downslope. Nope, go away.

I have a source for horse manure close by. We're talking about where the hay came from (and when worming was done). I'll take it but it will sit on a separate pile for a year, and we'll see if broadleaf weeds grow happily on it. If it checks out it will go into the garden NEXT spring. Time to be careful.

I just read an appalling article about herbicide being sprayed on thousands of acres of public forest land in California. Woodchips from public lands nearby that are left by the roadside had until reading that been my goto source. Turning perfectly good natural resources into toxic garbage to kill early succession plants that are often beneficial to regrowing native trees (ie N fixers) is insane.

Beans are a good indicator if you need to test for safety.