Plant of the Month
RSABG Volunteer, Nature Interpreter
Ceanothus crassifolius (hoary-leaved Ceanothus)
There are at least 52 species of ceanothus in the world. California is home to 43 species, sometimes known as California lilac, and 13 of these are native to the chaparral of Southern California. One of these is this month’s plant—Ceanothus crassifolius or the hoary-leaved ceanothus.
Plants of the buckthorn family (Rhamnaceae) in the genus Ceanothus are divided into two groups. The subgenus Ceanothus and the subgenus Cerastes. The latter is actually the larger of the two. I think that most of us, thanks to the showy displays in the Garden, seemingly in 50 shades of blue, are more familiar with the former that is characterized by thin leaves that have three main veins, arrayed alternately on the stems. The leaves of Cerastes are leathery with a single main vein, and generally opposite in arrangement.
Hoary-leaved ceanothus is in the subgenus Cerastes. It is a large evergreen shrub, which can grow to 12 feet in height. The tough-looking olive green leaves have white fuzzy undersides, which makes them hoary. The field guides I use describe the leaves as being small, which seems a bit vague. An Internet gardening catalog stated that they are 1/4" to 1/2" long. However, I took some measurements on a specimen in the Garden and found them to be closer to 1" to 1 1/2". The small (truly about a quarter of an inch), rounded flowers are white with the inflorescences borne on short stalks.
Hoary-leaved ceanothus is distributed through the Outer South Coast Range, Transverse Range, Peninsular Range and northern Baja on dry ridges or slopes below 3,700 feet, so locally we can find it in the Verdugo, San Gabriel, Santa Monica and San Bernardino Mountains. The plant I used for my observation in the Garden is on the path starting opposite the Lantz Outdoor Classroom leading west toward the Thorne Council Ring. The bush is on the right-hand side; if you pass the palo blanco (Ornithostaphylos oppositifolia) on the left, you have gone too far.