Generally, as you climb in elevation, temp. These factors effect what grows where and also how plants grow. Steppe, yellow pine, grand and douglas fir, sub-alpine, krummoltz and alpine are lifezones which will be encountered in the park. Trips with WI are primarily limited to the yellow pine and grand and douglas fir zones.
Edible berries are plentiful.
Particularly if you are going into high and remote areas, take good, light rain gear and a tent. Warm, waterproof clothing and a tent are virtually mandatory for spring, fall and winter trips into the backcountry. Heavy snow and rain, depending on elevation, characterize the North Cascades from fall into spring. The lives of the Native people of the North Cascades were closely tied to the natural environment and vulnerable to changes in the abundance or scarcity of the resources they depended upon. The Native people lived for thousands of years in the mountain environment.