California yerba santa is a flowering perennial shrub known botanically as eriodictyon californicum. It is a species in the waterleaf family of plants, which includes baby blue eyes. California yerba santa should be pruned in the spring or just into summer to preserve bloom. It has been grown for use as an herbal medicine treatment for centuries, as a food source for bees and is also planted naturally to stabilize eroding soils.
Harvest yerba santa flowers and leaves for tea and other holistic medicine purposes in the fall when the leaves are at their peak fragrance. Cut down mature seed heads in the very late fall or early winter to capture and save the seed which will otherwise self sow if allowed to remain on the plant.
Cut back any damaged, dying or diseased foliage and stems as you see them throughout the year. Prune down to the desired stem length past the damage, and place the cut at least 1/4-inch above a leaf node. Prune down stems to control the shape and size of the plant if needed, removing no more than 1/3 or the shrubs foliage bulk in any pruning session to limit stress on the plant.
Hard prune your yerba santa in the early winter or early spring in climates where the top foliage does not overwinter. Shear off all the foliage to just an inch or two above the crown of the plant, and toss the cuttings onto the compost pile. Mulch over the sheared crown with a few inches of compost, shredded bark or cocoa bean hulls if hard pruning in the winter to give some protection from the cold and winds.