I did the same thing last year and lost most of the ones I'd planted under the straw.

Mine (uncovered this year) have died back somewhat from their fullest, but they'll probably start greening out again fairly soon...

Mine, here in Oklahoma, never fully die down to the ground, even when we get to -16 F, like last winter. I wonder if you might not have something like slugs, under the straw, eating your onions?

George
Tahlequah, OK

I never mulch mine here in zone 5. They have died back but now kinda look like spring onion plant starts. I would look under the straw and see if the bulbs are still alive. dd

Ditto on not mulching over the Winter. Walking onions are exceptionally hardy, mine have survived for 18 years without mulch - and it gets pretty cold up here. All the mulch can do is harbor insects, slugs, & rodents. I do throw some compost on in Summer, though.

They usually begin growing again in the Fall, which is a good thing - you get two seasons of scallion production. They are both the first & last vegetable I harvest each year. The tops die back a little when the ground freezes... but they almost burst up through the snow in Spring.

You don't have to divide walking onions, but for the best results, I recommend doing so. The best time to dig them is in mid-Summer when they go dormant. I've also divided them in late Fall, when I plant my garlic; at that point they look like scallion plants. There is no need to rotate their location, you can just replant them in the same place.

Alternatively, to keep the patch healthy without digging, you can carefully harvest all but 1-2 plants from each clump in the course of the year. The remaining plants will divide to fill the space.

If divided into single plants in the Fall, walking onions will split from the base again in Spring, and produce bulbs large enough to be useful (1.5-2" across). I get those results even in half-day sun, next to my East wall. These bulbs are good used fresh (very strong!) but have virtually no storage life.

There are quite a few heirloom walking onions floating around; I presently grow 5 of them. Some vary in the color & size of the topset bulbs, and they also vary in the degree to which they multiply. Some will split at the base into 3-4 large stalks each year, others into 10 or more smaller stalks. They are my favorite scallions for flavor.