"Fresh" plant food in winter

From a friend i heard... A guy opened the bottle and inside there were plants, and we could eat them. It was in the winter and we were eating this green meadow plants.

What do i have to look for? Is it like sauerkraut, or what?

There are a number of ways to pickle greens.  Some you do like 'kraut, a little salt and natural fermentation.  Some do better with an acid pickle.  Other than 'kraut recipes with mixed veggies, I haven't played much with this, but the recipes are out there.

I am able to find a few plants in the winter...like chickweed, dandelions greens, and violet.  The chickweed stays alive under some snow.  I will get out more this winter to investigate what I can find.  There should be some root crops that could be harvested. 

You can find and eat leaves from wild strawberries, blackberries, raspberries etc.

The inner bark of some trees, such as slippery elm and siberian elm, are edible and can be harvested in winter, in a pinch.

Plankl wrote:
From a friend i heard... A guy opened the bottle and inside there were plants, and we could eat them. It was in the winter and we were eating this green meadow plants.

What do i have to look for? Is it like sauerkraut, or what?

You can sprout seeds anytime.

Might ask your friend for more details.  Could be he used a bottle as a container to freeze some greens like spinach, or as a bell-cloche for greenhouse growing of warm-season vegetables, or a magic genie.

Was the magic in the greens seeming fresh, or tasting "better than veggies," or being a deeper color than your friend had seen before?

Our region has lots of edible greens in winter, but it doesn't freeze hard. 
My lettuce and kale survived even the hard frost last week, I think the spinach and parsley still have some leaves on them, and the arugula is in its second crop. 

I also eat the 'weeds' people mentioned like chickweed, sorrel, sheep's sorrel, clover, violet leaves, dandelion.  It's not hard to get enough baby greens for a salad now and then, mixing cultivated and wild for good flavor. 

There's also fir and spruce tips, if you're really craving wild vitamins. Licorice fern (rhizomes, not leaves).  And technically it's still winter when the new leaves start coming out, like oso-berry (Indian plum), bigleaf maple flowers, dock, plantain, things like that.

Mom's Oregon Grape has some of the fattest, mildest berries this time of year.  A few at a time are good, not too much, and I spit out/save the seeds. 

And we sometimes leave tubers in the ground - Jerusalem artichoke, potato, oca (oxalis tuberosum), carrots.  Not always the best flavor, but it beats watching them rot indoors when I don't have freezer space or time to can them.