I'm not sure the leaves do fall off the trees in TSW - though I have never really paid attention. Certainly in winter, the leaves are still on the trees (covered in snow).
Yeah as aero says above the leaves don’t fall off trees. Tbh it’s not something I have paid to much attention to until you mentioned it.
If they are coniferous then throughout the year, like a dog or cat moulting. Oh except for larch which does lose all its leaves in the autumn. Time to take my rest in the (northern arboreal) forest I think!