I've had a similar experience... had a clump for years and then once year it just doesn't show back up in the spring. I starting letting a few seed down so you can rely on a following generation

They're also very late to emerge usually, so I would maybe give it a few more weeks before writing them off. I have a few clumps of A. incarnata that are just now poking through the soil surface by an inch or two.

I'm also wondering if I need to water -- I noted some other plants are wilting already (!!), no rain forecast in the foreseeable future, so I'm going to hand water the plants today (sprinkler will destroy the tree peony blooms) and see what they do in a few days.

Yeah, mine haven't popped up yet in z8. They're just slow!

About 6" tall here in southern MN. They seem short-lived to me. As soon as I think wow that's impressive they die out,. I let the seeds go and select where I want them.

They are definitely later. I have some in a bed in their fifth year. We are having unusual heat and nearly everything else is jumping up early. They are not. We have also been very dry. I had one last AI showing no growth when the others had shoots, and just yesterday I scratched the dirt a bit and saw some baby shoots coming up. Not sure why it was late. Bottom line, they are probably not that much later calendar-wise, but much later than everything else. Perhaps the lack of moisture affects them more, but I don't know. By the way, they are in very loamy soil that was amended with generous compost and peat. I think that has really helped them survive. The soil holds moisture but also drains well.

Did your milkweed come back?

"Did your milkweed come back?"

Yes, they did! I figured out why I saw no evidence of them -- something was chewing off the emerging stems, I finally looked very closely and saw hints of sawed-off green nubs poking through. I dug and potted all of those -- they are now filling in beautifully. The replacements I bought (because I wasn't sure these would bounce back) haven't fared so well -- got attacked by slugs, and also found a few milkweed weevils. AAARGH! So now I have to switch out the replacements with the originals. Who does that LOL!! (well I do, of course!). Interestingly, the blasted slugs couldn't seem to care less about all the luscious hostas I have -- they made a beeline to the milkweed clumps. Go figure.

I've been doing daily patrols, the pest numbers have been decreasing since I put out some diotomaceous earth and hand-picking any weevils and slugs I find. Beasts!

Yes, and deer also eat milkweed. That was what always was at mine. I sprayed and sprayed them constantly with deer repellent. I thought they didn't like the milky sap, but I guess that is for insects, not rats with hooves.