Tom is not only correct but is understating the case. They had no agriculture whatsoever. And the native plants are stingy with food, although the tribes did make use of the native dewberries (the blackberries are feral, not original) and one plant they were rather fond of was Camas. They died defending Camas meadows from rivals. (Don't mistake "Death Camas"--an unrelated and highly toxic plan, for Camas). Those succulent bulbs look pretty tempting, actually.
Another native plant, quite generous, that they probably made use of, was cat-tail. They are still abundant and were even more so before so many of the wetlands were drained.
There are also native blueberries and huckleberries. The evergreen lowland huckleberry is super-abundant.
I believe they ate both Salal berries and "Oregon Grape" (Mahonia aquifolia), which are both super-abundant, but have rather pitchy-tasting (but gelatinous--not sticky or gummy) fruits. I have heard of white people making jelly out of them, but the flavor is a little weird. I don't think they bothered with the native Currents, which produce small fruits that are not only pitchy-tasting, but kinda gummy. They are, however, technically quite edible (I've choked a few down out of curiosity). Just not tasty.
I don't think they ate mushrooms, which are super-abundant here mostly in the autumn, but some are "spring-fruiting". Of course you have to know which kinds, as we get both numerous gourmet mushrooms as well as a lot of species in the Fly-Agaric (a common mushroom here) and "Destroying Angel" genus. Oddly enough some of the most grotesque mushrooms are some of the tastiest, while Destroying Angels look more like a typical mushroom.
