So is this my failure point - or should I look elsewhere. Knowing this - can I feel safe composting these clippings - or should they not find their way to my garden, period. Input is appreciated. Been gardening for years - this one has me stumped.

Without that sort of help from you, we're shooting blind.

Fwiw, Triclopyr (Turflon) generally breaks down in 30-90 days depending on the time of year and exposure to weathering. It is systemic, so it will be found in the litter of harvested/sourced plant material. If you apply a high amount of litter that you apply Triclopyr to then you might want to wait 1-2 months before applying it to your garden even if composted (or 2-3 months in cooler seasons).

Triclopyr is a rather powerful herbicide even if it's effective breakdown is decently quick-ish considering it's strength.

Do you compost your tomato plants?

What else do you grow? Do you have problems with other plants? Do you compost those?

How is the sunlight? Are trees growing up around the garden and shading it?

Lesson learned .. care for the soil, and it will give back with bountyful harvest - kind of like some very dear scriptures I know. I like what Wayne5 said, "Leave the grass on the lawn".

Thanks for the feedback - Semper Fi !

If it's damaged by herbicides, then it's hazardous waste and must be disposed of appropriately.

Frankly, without knowing the underlying cause of the "failure," you're wasting time,money & effort. Curled leaves on tomatoes can be due to cultural problems, insect attacks and/or persistent broadleaf herbicides.

It's a chemical that totally breaks down, though one chemical it breaks down into is thought to maybe promote male infertility.

That said, the amount of contaminate of that "bad" chemical it breaks down into would be very tiny (and mostly harmless) coming from a breakdown of plant litter...and besides, that chemical itself is broken down to inert substances in a year or so.

Without images & a detailed cultural history, no one knows much about OP's garden failure. We can guess until we turn purple, but we still won't know for certain.

It's unwise to institute any sort of treatment without first obtaining a firm diagnosis.

Other herbicides can contaminate soil & compost for a long time, among them clopyralid. See this for info:
http://www.puyallup.wsu.edu/soilmgmt/clopyralid.htm

If in doubt about herbicide affected grass clippings, do as ken suggested: Leave them lie where they fall. (It's called grass-cycling.)

Since this stuff breaks down after a few months, it seems like overkill to me.

And it is most certainly not hazardous waste. The concentration in soil is extremely small. Unless a large amount of the chemical was actually spilled on the soil, it is nowhere close to being hazardous as far as waste disposal.

The link below includes a partial list of common products that are known to cause this type of problem. Turflon is not specifically listed, but another triclopyr based herbicide is.