고광나무속 Philadelphus LINN.

1. 꽃받침통에 털이 없거나 다소 많다.

2. 꽃받침통에 털이 많다.

3. 화반에 털이 없거나 있고 암술대에 털이 있으며 삭과는 타원형으로 끝이 뾰족하고 꽃받침 잎은 중앙보다 다소 위에 붙어 있다.

4. 꽃잎은 장타원상 도란형이며 화반에 털이 없거나 있고 암술대에 털이 있다.

5. 화반에 털이 없고 암술대에 털이 있다  ······················································································667. 고광나무

5. 꽃차례와 잎에 털이 있다   ··································································································668. 털고광나무

4. 꽃잎은 거의 둥글고 화반과 암술대에 털이 있다················································································· 왕고광나무

3. 화반과 암술대에 털이 없고 삭과는 도원추형이며 끝이 둥글고 꽃받침잎은 끝 가까이에 달리고 겉에 털이 없다.

6. 잎은 털이 약간 있거나 맥 상에만 있고 암술대는 중간 정도에서 갈라진다    ····································669. 얇은잎고광나무

6. 잎은 표면에 털이 약간 있고 뒷면에는 굽은 벌이 있으며 암술대는 위로부터 1/4 정도에서 갈라져서 젖혀졌다 ························ 섬고광나무

2. 꽃받침통에 털이 없거나 약간 있다   ···························································································670. 애기고광나무

1. 꽃받침통에 털이 밀생한다   ·············································································································671. 중국고광