We then began heading back into black oak savanna when we noticed a dandelion. I mentioned to Justin that there was another dandelion in the Chicago Region that I'd never seen, but that I wasn't sure how to distintuish it from Taraxacum officinale. Consulting Plants of the Chicago Region right there in the field, I read the key as Justin examined the plant. Conincidentally enough, we were staring at a new plant for both of us, Taraxacum laevigatum (=T. erythrospermum), the red-seeded dandelion. I bet you've never seen two seasoned botanists get so excited about a dandelion!
This species differs from our common dandelion in several ways. The terminal lobes of the leaves of T. laevigatum aren't noticably larger than the lateral lobes, while the terminal lobe is larger than the laterals in T. officinale. Also, the lobes on the leaves of T. laevigatum are divided all the way to the midvein, while the terminal lobe of T. officinale is not much divided or is divided only part way to the midvein. If flowers are present, you can tell the two species apart by examining the inner phyllaries, which are mostly flat at the tip in T. officinale and callous-thickened at the tip in T. laevigatum. Finally, the seeds in T. officinale are stramineous to brown, while those in T. laevigatum are deep reddish-brown.