After staying put nicely in one bed for years, it is spreading. I have pulled it all up so I can finish mulching. It has root runners similar to pulling up the vetch that tends to grow in my beds. Definitely a weed.

Someone told me this could be 'swamp candle'. I did a google search and to me it doesn't look anything like Swamp Candle or Yellow Loosestrife (Lysimachia terrestris). The mystery continues.

I think it is a lysimachia of some variety. See the pic in the link.

Here is a link that might be useful: pic

How about Lysimachia ciliata âÂÂFirecrackerâÂÂ, though yours seems a bit lighter red than some photos. Whorls of 4 leaves, and it has yellow flowers in the upper leaf axils. It is definitely a Lysimachia, and the root runners seem right for L. ciliata.

Thank you both very much! Not so much a weed as I thought. A much more manageable amount has grown back up. I'll let it mature and see if it looks more like 'Firecracker' or another variety of Lysimachia.