a true invasive in waterways .... might depend on your area ... it might be one for encasement in plastic and burial in a landfill... rather than the compost pile ... after it flowers .. get a full ID... and take the proper action ... ken

Ok, so the damage to my lysimachia nummularia seems to have stopped and new growth is re-flushing. The Golden Alexander is toast... gone. Skeletonized completely. So, I kind of assume that whatever it was is now gone. If it's slugs, I know how to control it. I tend to think it's not since there is a hosta right next to it and has NO damage. But if it's these sawfly larvae, how do you control them? I presume it's too late to do anything right now. In the spring?

As a follow-up to my statement about overwintering invasive plants in pots, I just want to restate that I am really only referring to plants that are invasive because they have running roots, not plants that reseed like Malva, Rudbeckia triloba or Euphorbia polychroma. The way that I overwinter my potted plants is that I use very large containers (at least 12" in diameter). All we do is take the pots and put them on their sides in an area where I am sure to have good snow cover. At the beginning of May, when the weather is warmed up and after the last frost date (which for Montreal is May 3rd - you can look this information up on the internet by city), we upright our pots. It works very well for all species that are hardy in Canadian Zones 5 and less (for me). Here is a link that might be useful: First and Last Frost Dates for Canadian cities

Just dig it up and plop it down. It transplants very easily. It also roots easily - spoken by someone who is a consummate failure with cuttings. You stick this stuff in the ground and it grows. May I suggest using vinegar instead of roundup? It works just as well, and no poison. The acidic jolt doesn't last in the soil, so don't worry about that. Your yard will just smell like a salad for an hour.