We have a flower bed in which we grow nothing but nectar rich flowers such as penstemon, hyssop, Fuchsia, monarda, salvia, Cuphea, columbine, honeysuckle, trumpet vine, butterfly bush, coral bells, apple trees, cherry trees and more. These are all pollinator addictive. In addition we raise mason bees which out-pollinate honey bees 100 to 1
In addition to attracting bees and butterflies, they are also very attractive to hummingbirds.

I'm reading 'California Bees & Blooms'; now need a good field guide to native wasps & syrphid flies, etc. Have been planting for our hive, & charting bee attractors by season; this year began i.d.ing many native pollinators as well. Most popular in our Calif. garden: asters, lavender, borage, many salvias, lambs' ears, thyme, rosemary, oregano (love the ornamental 'Herrenhausen'), calamint, sedum 'Autumn Joy', penstemon... Also trees & shrubs including toyon, coyote brush, & coffeberry, plus many annuals.

Photo: honeybee on left, native longhorn bee on right.