I know this is kind of a weird suggestion, but I was mulling over how winter could be improved, and thought "why not make that the weird season?". N. European folklore is really odd around yuletide, almost scary even. Adding curios and items that reflect this would make winter something to look forward to I think without making it something that would set you back if you missed out on it. I don't mean just another real plant, I'm talking about yulecats, gnomes, fairies, etc.
One idea I had was to have some winter decorative items produce "Yuletide spirit" that can be harvestable like a dream catcher, but only during yule. Things like snowmen, igloos, yule trees, garlands, etc. 10 of these could be crafted into a yuletide gift and given to a questgiver for another present in return. That present would essentially have a random item in it equal quality to the yuletide gift given to the questgiver. Mostly it could be natural gifts like forgeable curios from different seasons, curios like toy chariots, tar dolls, barkboats, reed ships, or rarely it could give crafted gifts like swords, clothing, armor, etc. Like the quest tree or rock looted it off of a corpse a long time ago.