Snap - mine are the same. I'd say snails as they leave a raspy mark. Go out after dark. They were having a snail fest in my garden - loads of them.

Yes, snail or slugs. Give them a beer fest (trap).

Thanks for your suggestions. You may well be correct because I've noticed both slugs and snails in the garden, but I'd never have thought they were responsible, so thanks again, I'll tackle the problem quicker than a snail's pace!

Might also be a bad case of gladiolus thrips - google and see what you think. Mine get it very year.

Bambo's suggestion is a possibility too(and a good one at that) since thrips scrape surface cells of leaves and flowers and suck up the plant juices released by the scraping. Since I do not use any insecticides in my garden, I have no idea of how to control them. I have found them in the gladiolus flowers so you might want to check them to see if you can find any for a positive ID.

Thanks also to Bamboo and Loosestrife. Thrips was suggested by an American friend last month, but I couldn't find any trace of the insects. Coincidentally, last night I set about "stalking" any passing slugs and snails and maybe word got out in their fraternity, but I never found a single one. One of my gladioli plants now resembles brown threads emanating from the soil -- there's no green leaves left.

I've never seen the thrips either, but then I've not looked with a magnifying glass, which I'd probably need these days. Mine do get it every year, but I just sort of ignore it, it doesn't start till quite late and they flower okay. I ignore it because those gladioli, by rights, should have died - they've been in a large pot on the balcony for 8 years, and still come up every year, thrips or not, bad winter or not... but they're set back out of the rain. The foliage looks appalling by October, shredded to nothing but a few strips.

Mine are the same. I kept inspecting for a month. Finally when the blooms started coming the pest starting becoming more visible. Tiny caterpillars.
I have pics but I can’t figure out how to post them in my comment.

You would need to post a new question attaching the photo to that, if you can, its not possible to attach photos to a comment...