Looks like a radish or aprickly lettuce....

But it isn't. I don't think anyway

 

It looks a bit like a roquette. I am not sure though.

 

I think more and more it is a roquette. The leaves have a nutty taste. Any other ideas.

 

As soon as it flowers I will snap a pic of that... sun tomorrow finally. I see a flower bud so I am sure it will open soon.

 

Roquettes make little white flowers like this.
Eruca sativa ialso known as roquette or arugula

 

Hi, Carolyn; maybe a TURNIP in early-mid stage of bolting...
Hank

 

funny... I don't grow either of these. but it does look like a garden plant waaaay away from the garden... back by the chicken yard. nor do we eat either of these.