Mom leans her head back against the wheelchair’s headrest to gaze up toward the tops of the redwoods. These forests are a kind of sanctuary for her, having lived amid such massive trees for more than 20 years. It’s an October afternoon in Samuel P. Taylor Park just north of San Francisco, and as I push her down the roughly paved path winding alongside Lagunitas Creek, home to spawning salmon, trees tower on either side. Ferns cover the shadowed ground, interrupted by lower sweeps of redwood sorrel that blanket the earth with their small, heart-shaped leaves. When sunlight touches the sorrel, the leaves fold downward to protect themselves, then right themselves once direct sunlight has passed. Amazingly adaptive, this species. Able to change when changing is required.