I've not been successful candling gladiolus seed. I just couldn't really tell. Fritillaria seed which are much more closely relate to Lilium and can look more like them, cannot be candled with surety either. Certainly, if you see an embryo, you know it's good, but if you don't, you just don't know. Back to gladiolus, there will be some where there is absolutely nothing there, but if there is anything at all, I would plant it. In addition, some species of glads look very different. If you are just starting out, the easiest species, in my opinion, is G. flannaganii.
