I have a new mystery weed, and no photo capability. I know it's a really long shot, but I was hoping someone might have a clue from description. Haven't been able to find anything close in searches or online weed keys. The inflorescences remind me of some sort of cress, but it may not be. Never seen a cress like this.

Full-grown, it is 2 1/2 to 3 1/2 ft tall. Stem is slender, 1/4 " max, and ridged. Leaves are compound, alternate, with about 17 small leaflets. The leaflets are irregularly and deeply lobed, and give the plant a 'ferny' look. Ligules are membranous, and go about halfway around the stem.

Most of the slender flower stalks are at or near the top, and long -- 6-10". The flowers are white, and are so tiny they are almost invisible. Below the current flowers at the tips of the flower stalks there are lots of thread-like seed pods on petioles. The petioles are about a half inch long, and the pods are 1-2 inches long.

The stems grow either individually, or as a number of stems from a single rootcrown, but without any rosette.

They are not deep-rooted, and pull fairly easily (which I have been doing as fast as I can since I saw all those developing pods.... each one seems to have 15-20 little developing seeds....) I've never seen these before, and suddenly this spring we have a small field of them.

I am trying to beat them back to nothing, but I suspect that I'll be fighting with them for a few years to come. I would love to know the name of my new foe.

Any ideas?