Most of them get yanked up, but some are showing up outside the yard fence in the pasture. This one just came up in a place that I thought was okay to let grow. Probably from a black oil sunflower seed which I used generously this year, but might also be from those striped sunflower seeds. The latter were in a couple of mixes that I bought. I also know that millet looks like crabgrass when it sprouts. Fortunately it doesn't grow as large and makes seeds when it's really a short plant. I'm guessing it's also a cool weather plant since it seems to suffer quickly on the warmer days.

That's fun! I usually only got the crabby grasses. I guess the birds took off with all the sunflower seeds.

We got a few big sunflowers in a pasture this spring. I believe they grew from the occasional seeds I see in the whole oats I buy. The ones that grow from the birdseed are nowhere near as nice.