One of the richest historical museums in Northern California is unfolding into a striking panorama at UC Davis. The University Arboretum has come to colorful life this spring with more than 2,000 varieties of trees and plants covering more than 150 acres along a two-mile stretch of Putah Creek. Redwood groves, walnut orchards, desert and Mediterranean gardens are found along the arboretum's many paths. The collection of trees and plants are grouped as they would be found in nature with an emphasis on plants that are adapted to the California's Central Valley climate. They range from the prickly pear cactus, with its edible fruit, to the California redbud that puts on a spectacular show in the spring. Arboretum volunteers provide public tours as well as care for the area's plants and trees, according to Diane Cary, the arboretum's administrative manager.