Do you have to lift gladioli?
A perennial problem is whether to lift half-hardy bulbs and corms (and tubers). Rather like the cannas yesterday, these frost-tender plants can be left outside in temperate climates with winter temperatures below zero – but only if they are planted deeply enough so that the storage organs (and their buds) do not actually get frozen.
That is why gladioli, and dahlias, can be left in the ground in winter in most areas of the British Isles. Whether you lift or leave is partly down to how you can store the lifted plants, how you will feel if you lose them, your location, your soil and other factors – so there is no easy answer, as so often.
Storage
Once the gladioli are lifted they need to be cleaned. The old stem can be snapped off the new corm and the old corm snapped off the base. Gladioli are corms and although I am often criticised for being pedantic about bulbs and corms, there is a difference. Corms are replaced every year and a new corm grows on top of the old corm. The old corm is useless to us but gladioli usually produce a cluster of tiny cormlets. If left in the ground these will grow and produce lots of ‘grass’ that won’t flower and, being crowded, will take a long time to bloom. If lifted and removed they can either be planted in spring in rows, like seeds, to grow on to flowering size, or discarded. Then the corms need to be stored in a cool, dry place, away from mice, till planting time in (about) April. If you can’t store them in this way, or you are forgetful, it may be better to leave them where they are!
Location and soil
How severe your winter is likely to be will affect your decision on whether to lift the corms. If you are in a cold spot then lifting is best. Soil makes a difference too. The corms are more likely to die if the soil is heavy (clay) and wet in winter. Sandy soils are far better. You need to consider pests too and slugs are more likely to feed on the corms, and new shoots, in heavy soils – especially relevant with dahlias.
So, to sum up, lifting gladioli is generally the way to go. But the corms are likely to survive in most areas in most winters. But you may get lots of foliage and not just flowers and if you have expensive or choice kinds you may lose them. Some kinds will be hardier than others and you may find a mix may eventually all be red or yellow – but that is a different question. And not all gladioli are the same – some are much hardier and I am only talking about large-flowered kinds here.
The Biking Gardener 
I grow only a few gladiolus and leave them in the ground. G. colvillei ‘The Bride’ has been hardy for many years though did get a set-back in the hard winter of 2010-11. It has recovered well since. G. byzantinus has proven to be almost a weed and G. tristis does nicely with extra drainage.
Ah yes, well that is why I did add the caveat about the gladioli. I once had G. byzantinus in an iris bed and it was a disaster! ‘The Bride’ was hardy for me in Courtown and did well. I have a potful here ready to go in and will see how it fares here.
Interesting. I’ve never lifted mine.
Blue Rock Horses Frederick County, Virginia bluerockhorses.com
I love gladiolus. My grandmother used to grow rows of them, I recall her cutting them and setting them in a vase on the table. I believe that they lifted them every year as I remember my grandfather pulling them out of the pump house to replant yearly.
I am never totally happy with them in borders but they are such lovely cut flowers and growing a row for cutting is possibly the best way to treat them.
Ours do not get dug either, but are not reliably perennial either. Frost is not a problem. However, a lack of chill can be a problem for some bulbs. Weirdly, the few gladioli bulbs that are perennial have been perennial for several years. I mean, when they were originally planted, less than half bloom for a second year, a few years later, only a few bulbs remained. However, those few bulbs have been blooming reliably for many years now. It makes no sense.
I suppose some plants will be better adapted to certain local conditions than others.
Oh yes; I get that. I like to think that this is the best climate for just about everything, but it really is not. Some things need more chill. Some of what I would like to bring up from Southern California dislikes even the minor chill we get here.