꼭두서니속 Rubia LINN.

1. 곧추 자라고 가시가 없다 ············································································································409. 큰꼭두서니

1. 덩굴성이며 가시가 있다.

2. 잎은 4개씩 윤생한다.

3. 털이 밀생한다    ···············································································································412. 우단꼭두서니

3. 털이 적다     ·························································································································410. 꼭두서니

2. 잎은 원줄기에서는 6-12 개씩 달리고 가지에서는 4-6 개씩 달린다.

4. 잎은 가지에서는 4-6 개씩 달린다    ·························································································411. 갈퀴꼭두서니

4. 잎은 가지에서는 4 개씩 달린다 ·····························································································411 +. 가지꼭두서니