I have to cut down this plant today and I will miss it.
This spring, it started popping up everywhere. I hoped it was an Aster or Goldenrod, and tried to wait until fall to find out. I ended up getting impatient and googled "light green plant with lots of leaves", like a genius, and found out it's Horseweed, Conyza canadensis. It's an annual plant with "insignificant flowers" according to the Illinois Wildflower Society. A variety of small flies feed on the nectar, and other insects eat the leaves and stem.
I let it grow all summer. I wanted to feed those tiny insects, and the plant kept me company in my barren, boring yard. Look at the composition of the third photo! It's my absolute favorite area and I love looking at it. So beautiful, without anyone doing a thing.
I have to cut it down today because it's going to seed. If I'm going to be planting trees or vegetables next year, 10 million Horseweed seeds in the soil could cause me some trouble. I attempted to cut it down last week and got sentimental, so we shall see if I can handle it today.
Oh, and the reason I'm cutting it down rather than pulling it out is to maintain soil integrity. Ripping it out would disturb the soil, opening it up to erosion and colonization by other weeds. Plus, Horseweed grows branches when it is cut, so I will still have the plants (no seeds) until the vegetation is killed by frost!