Thanks Tom, John, and Jane. If the timing is critical in this call, then I say late May-early June. I didn't remember the exact time but the Garlic-mustard was in full bloom all along the brook and field edge. I read that the plant dies off by end of June. What I can't find out is why the plant causes problems with people, like headaches and such.

from garlic mustard. They're more psychological headaches. Alliaria is a non-native plant which is taking advantage of the poor health of our natural communities (usually woodland) for its own benefit, the way a cold bug takes you over when you're not getting enough rest, etc. And just as the cold bug makes you worse, so does Alliaria worsen the health of our native woodlands. It multiplies prolifically and its life style as a biennial gives it a headstart on the natives in spring. It steals their sunlight to produce millions of its own seeds, while the natives barely get enough energy to survive to next year, but probably not enough to complete seed production themselves. There are many woodlands from Illinois to the east coast where Alliaria is about the only plant you'll see. The entire native flora, spring, summer, and fall is starved for sunlight and slowly dies out. Add to that the non-native shrub Buckthorn and the groundlayer of some woodlands are completely bare in the summer. Those of us in natural area restoration work spend the entire months of May and June bent over in the woods, pulling this plant wherever we find it, and then the entire winter, cutting and removing buckthorn. But we're making progress and the native plants (and their insect friends!) are coming back strong!

Ah. I see. Well we do have an awful lot of Alliaria in this area. Moreso this past summer than the years before. Looks like I will have a new yard job in the spring. Very informative, thanks.

the populations of West Virginia and Mustard White butterflies are declining at least here in the east. The females will lay eggs on the garlick mustard, and when the caterpillars eat it, they die.

garlic mustard on which it is resting, we would say this image is mid to late May. Our muscles hurt just to look at it!