When growing in a planting bed, the easiest form of removal is to dig each clump out. Time consuming I know, but this is really the most effective way to remove all the tubers and bublets from which this plant grows and also its primary means of spreading. Since this is a spring ephemeral - disappears soon after flowering until reappearing early next spring - now is the time to do this, especially before any flowers have time to set seed.

I had this in my old garden - actually the more desirable named forms like Brazen Hussy, Dusky Maiden and Damerham, but they all reverted to species. I was pretty diligent about weeding out extras and keeping it confined to a single area and so did't actually object to the plant too much since it disappeared pretty early in the season. But it is one of those plants you simply cannot ignore or it will spread vigorously into parts of the garden you do not want or worse, into wild or natural areas.

Thanks, as always gardengal. How about the judicious, and sparing use of roundup?

Sure - that'll work quite well. The issue is it will also work quite well to destroy any adjoining plants too, so you need to be extremely cautious in your application if nearby any valued plants.

I use hori hori knife the get deep under the bulb and pop it right up. It's one of these plants that will regrow from tiny bulblets left behind. That's why it is so hard to eradicate, takes time and diligence.

If using herbicide I would go with paint rather than spray method to protect nearby plants from possible drift but this seems not practical if the infestation is large and it is in your case. If I were you I'd contact a local Master Gardener and ask about suggested and approved methods of removal.

Thanks for the advice. The patch that's primarily in is bare so not really anything else to kill. I may employ a little of both. I don routinely use herbicide, if at all. But I've found using it surgically has had good results. I used it it to almost completely eradicate morning glory. Now it's just maintenance. I think I'll do the same again. A little over time. Keep it contained and gradually eradicate. Thanks again.