One great plant that's often overlooked as a choice for the bee garden is flannel bush -- also referred to as California fremontia -- (Fremontodendron californicum). While the species is sometimes available, you're more likely to find one of the cultivars. Look for this plant at specialty nurseries or well-stocked independent garden centers. The species and its cultivars 'California Glory', 'Pacific Sunset', and 'San Gabriel' are quite large, reaching up to 20 feet in height. The cultivar 'Ken Taylor' is more manageable for a small garden; 'Ken' will reach up to six feet tall and 10 feet wide but can be kept smaller with pruning.
Here's why flannel bush makes a great choice for the California (Sunset zones 4-24) bee garden:
1. It's an attractive, eye-catching plant. The large, 3-inch wide flowers cover this plant at peak bloom. You may have noticed large plants along California highways that are covered in yellow flowers come springtime. That's flannel bush...from California Native Plants for the Garden: "A California fremontia in full bloom is an unforgettable sight." This plant was photographed at the Old City Cemetery in Sacramento.
2. Going low water? Flannel bush needs NO summer water, in fact summer water is HARMFUL to this plant. Like many of our California natives, it evolved in hot, dry areas in the absence of the root diseases that are favored by warm, wet conditions. It thus has no defenses against these diseases.
3. Fast growing. Flannel bush grows quickly; you'll have lots of bloom by the second year after planting. This also makes it a good candidate for an espalier. The best cultivars for this are 'California Glory' and 'San Gabriel'. This photo of 'Ken Taylor' was taken one year after planting, at which point is was already about 4 feet across. This cultivar, which is a cross of the Sierra foothills species Fremontodendron californicum decumbens and 'California Glory', has a prostrate form that looks nice on a bank orberm. This is also a great way to provide the excellent drainage this plant needs. Another small (3 feet tall by 6 feet wide) flannel bush is 'Dara's Choice', which was introduced by the Santa Barbara Botanic Garden. It is a cross between Fremontodendron californicum decumbens and Fremontodendron mexicanum. 
4. Fun fact for plant nerds....flannel bush nectar fluoresces blue under UV light. Amaze your friends and family with this neat trick! This was first observed by UCD Entomology's own Robbin Thorp many years ago (Thorp, RW et al. 1975. Science (189): 476-478). This property has been observed in many plant nectars and is thought to provide a visual cue to foraging bees (remember that bees see in the UV spectrum).
5. Flannel bush nectar is nutritious. It is rich in isoflavenoids, which may have antimicrobial properties helpful to bees (Scogin, R. 1979. Bot. Gazette (140): 29-31).
We have Fremontodendron californicum and the hybrid 'Ken Taylor' at the Haven. There are also several nice specimens at the UC Davis Arboretum. This plant is at its best in early spring. One note of caution: some people are irritated by the small hairs that cover its leaves. Plan on wearing gloves and long sleeves when pruning.