Of dog fennel: "The stems and base are covered in leaves so dissected that they resemble green hairs coming out of the stem in fractal patterns. When crushed, the leaves and flowers smell rather unpleasant." (Ask.com)
This small weed is growing at the fence between us and the neighbor. I believe it is dog fennel, which I've noticed growing in one other spot in our back yard (among the rocks of the terrace, getting about two feet tall before being cut back in the bi-weekly summer edging). It may be one of my favorite weeds, so fern-like and delicate when young, and I am hoping that my string trimming mate will allow it to live out its life unmolested in the safety of our yard.
From all I've read about dog fennel, it is not a toxic plant, but can cause skin irritation. We can live with that.
An unlikely time of year to be growing, but I think the warmth of the brick it happens to be growing against has something to with its successful germination. This is a part of the yard gets a long stretch of midday sun that is warm even in the cold of winter. Booker chooses to sun himself a few feet away, a sleepy-eyed Sphinx with a stick.