How about licorice fern?Also in seattle and such nettlesshould be poking their heads out soon.By mid march you can start collecting in earnest for next winter.(I collect 4 dry gallons per person for an entire winter).How about wintergreen leaves.They should have red berries this time of year but the leaves would be what to gather for tea.More a landscape plant.
There is nothing permanent in a culture dependent on such temporaries as civilization.
I've been drinking doug fir needle tea about once a week to get an extra shot of vitamin c. Not much out there during winter, but goat is right about nettles, young ones poppin up soon. Dandelion root and plantain seed tea are good right now too. THere might still be some good rose hips too.