Hi Molly.
I have to admit, I have the same problem sometimes. I've been growing seeds for several years but still can't ID many seedlings. But in my head they fall into certain categories and I know that they're not weeds. I can't always distinguish rudbeckia hirta from gaillardia or echinacea, but I always know it's one of those. I gave my friend a seedling last year which I thought was a rudbeckia, it ended up being an echinacea. Oh well, it was pretty and not a weed!
I also have trouble differentiating larkspur, nigella, and California poppy, but i know it's one of those three.
It is a good time to direct sow those larkspur that we talked about. Really early fall is best, they germinate and winter over as tiny seedlings. They are very cold hardy and have no problem surviving all winter even in below zero temperatures. They might wilt and pout a little but quickly recover. But if you sow them now they should germinate at first sign of spring and do well for you. Mine do best (i.e. get taller) in full sun but some that I grow in morning shade, afternoon sun are nearly as tall. They don't demand too much water.
Once you get a crop established they'll self sow and you'll never have to sow them again. It's worth an investment in a good quantity of seeds the first time to have them forever.
Here we have been buried in snow for weeks so I haven't seen my flower beds. But here's one of my beds taken in January before the snow. See the green blanket covering the bed? That's about 95% larkspur! And after single digit temps with no insulation from snow.
Karen