This month’s cover drawing by Bonnie Walters is a repeat of flannel bush, Fremontodendron californicum. It was last used on the Obispoensis cover back in 1991. Does anybody remember it?
It is being reused now due to a request Bonnie received to use some of her drawings for a project associated with “Learning among the Oaks” program. Of course, this required us to go back into our archives to find it. Also, it was obvious to us that the write-up that accompanied the earlier cover was clearly out of date. Back then the article stated that flannel bush was “a member of the moderately large (65 general and 1000 species) and predominantly tropical family, Sterculiaceae. The most famous member of this family by far is cacao, Theobroma cacao, the plant from which from which chocolate is made.”
Today we have to accept the conclusion that flannel bushes are part of the large (266 genera & 4025 species), cosmopolitan (but still favoring warmer regions of the earth) Malvaceae. This family is most often called the cotton, hibiscus or mallow, and obviously chocolate family. The most obvious characteristic shared by flannel bush and the rest of the Malvaceae is the fusion of their stamen filaments into a tube that completely surrounds and thus hides the ovary and style base. One other note, the beautiful yellow perianth elements found on flannel bushes are sepals not petals; Fremontodendron does not have petals. This is because there is only one whorl of perianth and when that happens, botanists almost always define them as sepals.
Back in 1991, it was noted that Fremontodendron in California had only two species – F. mexicanum and F. californicum. In 2013 we have to acknowledge that there are now three recognized species. A new species with a very restricted range (found only in Yuba & Nevada Counties) has been separated from F. californicum. This new species is F. decumbens or the Pine Hill flannel bush.
Unlike the other species which are erect, small trees or large shrubs, Pine Hill flannel bush grows flat on the ground. The new Jepson Manual indicates that this species is “morphologically, genetically” distinct (i.e. looks different and doesn’t cross with) from the other species.
Use in the Garden
As one might guess because of its large flowers, flannel bushes ought to be sought after as horticultural plants. The problem is that they are considered hard to grow. They require well drained soils with little summer water. If one tries to plant them in clay, such as found around San Luis Obispo, one internet reference recommended digging a large hole (three feet across and deep) and filling it with sand before planting. This will keep the soil in contact with the root crown from prolonged contact with moist soil. Summer watering (after establishment) and/or moist soil in contact with the root crown will kill it in a couple of years.
The pure species in cultivation is mostly F. mexicanum as it has the largest flowers. However, this species is restricted to extreme Southern California and adjacent Mexico. Because of this, gardeners have created hybrids and selections that combine the environmental latitude of F. californicum with the large flowers of F. mexicanum, thus making the hybrids much more garden friendly.
Gardeners on the internet stress that flannel bushes are large plants and don’t fit well into small suburban settings. They also noted that the pubescence (hairs) that shed from the twigs can be very irritating. Therefore, it might be best to plant it where people do not congregate.
Fremontodendron in the Wild
F. californica is found in desert washes and on dry, well drained foothill slopes. It is particularly common in the high desert and southern Sierra foothills where it prefers locations soil surfaces are habitually dry yet have available water from relatively shallow water tables. This is because their root crowns are particularly susceptible to various pathogenic fungi that live near the surface. It is these soil pathogens that make it difficult to maintain in cultivation.
Viewing Flannel Bush in SLO County
It can be found in our county in scattered colonies along the crest of the Santa Lucia Mountains and on a few of the higher peaks in the interior. The most accessible stand is just east of the forest service road to the Sergeant Cypress Grove on West Cuesta Ridge. Most of our plants have smaller, three-lobed leaves instead of the more common five-lobed leaves characteristic of the species. Because of this Dr. Robert Hoover named our local plants, F. californicum var. obispoense. I also think I remember Dr. Robert Rodin, a plant anatomist and morphologist, telling me that the flannel bushes on West Cuesta Ridge also had one less chromosome than the rest of the species. If this is true, it would further strengthen the separation of our plants into a distinct variety.
A Local Hybrid
I have one last note. A member of our chapter enters the story of producing a much more water-tolerant Fremontodendron garden. This cross, between Fremontodendron californicum and the tropical monkey’s hand tree (or Chiranthodendron pentadactylon) was being propagated for eventual release into the trade at Rancho Santa Ana by then Rancho graduate student and later SLO County Chapter member Austin Griffiths. At least one of these inter generic hybrid plants was planted on the Cal Poly campus. I do not know if it is still living there.