They look like sunflower seedlings. Did you have a feeder or plant close by last year?

I think sun flower also but frost should have killed it.

I bought a bad of mixed bird seed this year that had sun flower seed in it. I would throw out seed in bad weather, but only in the driveway or other bare areas, but nowhere near the garden. If sunflower can go through a bird and still sprout, the seed could have been some I tossed out or from my son's bird feeder ( he feeds all year) . The birds perch on my tomato trellises and feed in the garden all year long.

Thanks for the input. Larry