Is there a quick way to tell if they are viable? Are they like Lilium seeds in that only some of the papery seed coverings contain viable embryos?
Thanks,
Alana

all new to me.. sorry

Well, just like in a lily seed pod, usually the "top" ones towards the opening in the pod are bigger and better seeds.
But you can just emptu the pod on a newspaper and by comparison, choose the big ones.
You should feel/see there is something inside not just a see-through thing.
I never sowed any gladiolus seeds cause there's so many small corms in the ground surrounding the big one.
And also, I am not sure this Gladiolus comes true from seeds... there may have been so much hybdridizing going on... unless you have some species gladiolus (like, wild type)

Thank you for your response. It is good to know that the larger seeds are better. I've never grown any Gladiolus species from seeds, but I have noticed that they are papery thin and crammed into the seed capsule in a similar fashion as Lilies, so I was curious if viable seeds were identified by "candling" as I have done with some Lily species.
I'm sure the hybrids will not come true from seed.

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.