Posted: 03/04/2017 at 19:20
Those look like sycamore seeds ....... don't panic ..... just mow your lawn regularly and they'll die.
If you left them to grow you'd have a forest, but at that size they don't survive having their tops lopped off. I promise you that's the case. We have similar ash tree seeds all over our lawns every year. All we do is mow the lawns.
More of a nuisance are the ones that fall and germinate on the flower beds - I hoe those out before they get more than a few inches tall.