Ask-a-Dave's-Gardener: Please help me identify these tiny sprouts on outdoor net, 1 by PuraVida4Me

PuraVida4Me wrote:
Greetings,

I recently discovered a small group of about 8 tiny (3/8 inch) sprouts in one of the openings of our outdoor net covering our wine grapes. They showed up around mid-August. We are located in Mariposa, California in the foothills of Yosemite. The heads of the sprouts are white and the stems are clear.

Has anyone seen these before? Are they an airborne invasive?

I mend the netting almost daily as birds like Bullock Orioles find their way inside and need to be rescued.

The sprouts shown here are the only group of sprouts that I have found clinging to the nets. The net openings are about 1 inch by 1 1/2 inches. Thank you for any information that you can share with me.