It's not swiss chard. It's a brassica of some sort. Reminds me of daikon radish leaves.

Rodney

Previous discussion of same plant https://www.houzz.com/discussions/6313552/is-this-swiss-chard#n=7

I suggested you dug one and looked at the roots. Did you? Seeing those would be very helpful.

Swiss chard does not have lobed leaves.

"Mustard" is correct in the broad sense unless you see some sort of root vegetable forming, but there are many different types. Reminds me very much of how my Mizuna grows except the leaves are more rounded with yours. Don't know if some type of Arugula would grow like that.

You have no idea what you planted? Do you remember the choices?

Being a root vegetable does not preclude being a mustard. Radish, turnip, rutabaga, kohl rabi ... they’re all Brassicaceae, ie mustards.

here's the roots. 2 plants are a darker green. they were getting clusters of buds & 1 bloomed while i was out there.

The flowers say Arugula or Daikon.

That looks like arugula (rocket) to me. The flower looks like arugula, too. Radishes can have a flower like that, too. But most real mustards would have a yellow flower.

i looked photos of arugula rocket & i'd say that's the winner. there were arugula seeds in that batch. i've never grown rocket before. i've only grown the variety that is taller & has smaller leaves & yellow flowers. thanks to everyone.

Arugula and rocket are synonyms, Eruca sativa. The one with yellow flowers is wild rocket, Diplotaxis tenuifolia.