"California" being the operative word, there. Oslo, Norway has a 60 degree latitude. Sacramento has a 35.8 degree latitude.

Most humans live closer to 27 degrees north of the equator. I mentioned California natives because that’s what I’m most familiar with. Plant preservation is a thing in northern latitudes too..

Natives in California can still be harvesting in November and can see the ground all year round except in the mountains. Natives at the far north might be done with harvesting by late September or early October and might not see the ground again until April. Not even remotely comparable in terms of the severity of the issue and the impact to survival.

Natives in the far north still preserve food for consumption during winter months.

Sure, the plants are alive as roots, seeds etc under the snow, but they have nothing edible to offer, so for the purposes of nutrition, they might as well be dead.