California Buttonbush (Cephalanthus occidentalis):

This beautiful plant is a deciduous shrub, generally growing 3-9 feet tall, however it can grow up to 20 feet as a tree! These white-yellow, spikey button flowers bloom in the spring and are loved by native bees and butterflies. You’ll often find this plant by streams and in wet locations. At the Preserve, it grows just below the first wooden bridge at the Visitor Center trailhead. Feature in this photo is the swallowtail butterfly. In addition to bees and butterflies, the plant is loved by native waterfowl who utilize the seeds for food.