Triclopyr production is rather low-key stuff, but it's very powerful in it's effectiveness. It mimics a natural auxin/hormone and signals a plant to start uncontrolled growth which busts cells and demands more out of a plant than it could hope to provide. It's basically oxamic acid (found in spinach in measurable quantity, fwiw) and catalysts mostly driven by (and consumed with) CO2...which, btw, are 2 of the main chemicals it breaks down into (oxamic acid/CO2)...along with a few other organic acids like TCP (in small amounts) and TMP (even smaller amounts, and not produced via water degradation). Now, TCP exposure has been linked to lower sperm counts in human males...but the TCP produced in this breakdown is extremely weak, a small amount, and rarely persistent...especially in water and moist soil (nearly non-existent in air). The continuing breakdown from Triclopyr to TCP/TMP compounds to CO2 and lesser organic acids (such as oxalic acid) is rather quick.. If it's applied properly (aka, not getting it all over you...because it's a mild skin irritant, too) it's not much of an issue...especially considering how extremely low it's toxicity is in the air. It nearly fully breaks down REALLY quickly in the presence of direct light (minutes to hours). The further breakdown of TCP/TMP mainly becomes CO2. Aside from the small amount of time the breakdown consists of TCP, there's no "red flags" in the production or degradation productions of Triclopyr. Even the low-sperm count alarms of TCP aren't much of an issue considering how little of it that is produced and that you're going to have be putting bare hands all over soil where Triclopyr has been recently applied in order to get it on you...unless you're improperly applying it and getting it all over you...which you'd know because it's a mild skin irritant because of the quick chemical reaction changes that occur once it's exposed to the environment (especially direct light or moisture).

It was probably a window of ~ 24 hours between the application of the weed killer and when I watered them. I did try to water both the foliage and the soil beneath the plant. We've also gotten some sporadic rain during the nights during that time as well. I didn't spray the perennials directly; There must have been some drift that day - it was pretty breezy out. I've noticed that the hostas have developed a slight mottling of the leaves. They have specks that remind me of touching notebook paper with greasy fingers - an off-color, translucent look. But the Annabelle just curled up a bit. In fact, some of the hydrangea's leaves and stems appear unaffected at all. Maybe I dodged a bullet...?

Thanks for replying back. I feel less concerned now as your thoughts are very logical. The plant sent up about six stems and lots of leaves and that seems like a lot of work for a young peony. I know I'll be checking it out next spring, hoping for buds! Lord willin'.

Couldn't hurt to try - and I'd hurry up. If it's roundup for example, rain will wash it off - but it's "rain-safe" in only 30 minutes or so. I think roundup is neutral once it's on the ground, it just kills plants from the foiliage. So I'd rinse the heck off of the leaves. You might ask the neighbor what they used also, to know what you're dealing with. I'm just guessing at roundup, since it's pretty common - certainly could be something else. Best of luck, I hope they're ok.