By Sharon Reeve, for Let’s Talk Plants! July 2022.
A favorite plant - Calliandra californica
California Fairy Duster or Baja Fairy Duster, Calliandra californica, is one of my favorite plants. There are several of these beauties planted in my garden because they are stellar performers. They seem to bloom all of the time! Going by the name, you would assume that this plant is from California, but you (and I) would be wrong. The species name, californica refers to Baja California and not our lovely state. The species is found in Baja California Sur, mostly in the upper regions of the Central Desert down to Santa Margarita Island and a few populations are sprinkled in the Cape Region. This is a plant that can be found where water occurs in gullies, seeps, and washes, and is reported to grow on low alkaline hillsides. My references also list it occurring across the Gulf and further east into Sonora, Mexico.
(Figure 2) Primary Range of Calliandra californica.
Botanical Classification The genus Calliandra is in the plant family Fabaceae and the name means "beautiful botanical classification.”
There are three members of Calliandra in Baja California and approximately 135 species (Kew) worldwide, mainly in semi-tropical and tropical locations in the Americas. Two species were recently found in continental Africa, nine in Madagascar, and two from India. Most species occur in Brazil, Mexico to Central America, and in Northwestern South America. Three species occur in Baja California, and one occurs in the United States. The Fabaceae is further divided into three subfamilies based on floral characteristics. Members in the Fabaceae fix nitrogen with species of symbiotic Rhizobium bacteria. Calliandra is in the subfamily Mimosoideae, which is distinguished by actinomorphic flowers, meaning that the flowers are radially symmetrical, and have five fused or separate petals. Other characteristics of Mimosoidaceae include straight fruit with swollen margins, which open explosively from the apex to the base. In the case of Calliandra californica, the five petals are fused at the base of each flower and form a tubular-funnelform calyx shape with five lobes. The most striking characteristic of the flowers is the long (17-25 mm) bright red stigma filaments that number 17-26 per flower. The flowers are formed in berry-like clusters of 8-12 flowers, that bloom simultaneously to form one large cluster of striking showy stamens (Figure 3). The leaves are bluish-green and evenly bipinnately compound with 5-15 pairs of leaflets. The leaflets close at night, by folding up along the mid rib. This response to darkness is also called nyctinastic closure or "sleep movement." This movement is facilitated by anatomical thickenings at the base of plant leaflets called pulvini. Pulvini are common structural adaptations in Fabaceae. In some species of Fabaceae, the pulvini responds to touch, rather than light, in a process called thigmonasty or "touch movement." A well-known example of thigmonasty is seen in Mimosa pudica or "sensitive plant." Like other members of the Fabaceae, seeds are contained in flat felty pods that open along the seam from the distal end and explosively eject seeds as far as six feet away from the plant. Spent pods remain attached to the shrub for an extended period.
(Figure 3) Flower bud clusters and opened flowers of Calliandra californica. Photo S. Reeve.
(Figure 4) Showy stamens and seed pod of Calliandra californica. Photo S. Reeve.
Calliandra eriophylla Southern California does have a native Calliandra, Calliandra eriophylla or Fairyduster. In Spanish it is referred to as Huajillo, Cosahui, and English translations of other names are "Head of the Angel” or “Hair of the Angel." Eriophylla refers to the woolly leaflets. This rhizomatous, densely branched, unarmed species is smaller at two to three feet tall and four feet wide and occurs in Creosote Scrub habitat in eastern San Diego County and Imperial County. It is frequently used in erosion control. Calliandra eriophylla is deciduous in drought or in excessive cold conditions. Its large range extends into Arizona, Texas, Baja California, and Sonora, Mexico. Calliandra eriophylla is drought tolerant and survives on three to nine inches of rain a year. In my garden, this plant does not seem to bloom as long as Calliandra californica. References list the bloom period as late winter to early spring, although further reading says additional water can boost the bloom period into early summer. Fall rains will frequently result in an additional bloom. The stamen color varies and can be white to pink to red (Figure 5). My experience with the plant is at odds with the text. I find the leaves are greener than the bluish-green leaves of Calliandra californica. Fairy Duster is root hardy to five degrees Fahrenheit and slightly more cold tolerant than Baja Fairy Duster. This plant needs some selective pruning to keep it looking its best. Removal of twiggy growth and shaping will bulk up the airy nature of this shrub. Both species look better with heavy pruning after damaging freezes.
(Figure 5) Calliandra eriophylla. Photo Paul Asman and Jill Lenoble.
Calliandra californica I love this plant! The overall shape is a pleasing vase shape even without pruning (Figure 1). Some reference texts talk about how slowly this evergreen shrub grows, and again, this has not been my experience. I have one in the ground that is full height in less than a year, but I suppose it is in an above average situation, and this may not be the normal growth rate. This evergreen shrub matures at five feet tall and about six feet wide. Other texts refer to Calliandra californica as having a "fast" growth rate, and the difference, I think, is in the situation of the observed plant. I believe that in desert-like conditions with full sun, fast drainage, and drier air the plant grows faster than in coastal situations with less heat and sun. Well-draining soil is better for good growth, but the plant is adaptable. In my slightly inland garden it has been fast, and I am sure the supplemental irrigation helped! I find the foliage is a very pleasing steel bluish-green that I find lovely juxtaposed with the bright true-red stamens. My plant has bluish foliage and I assume there is a natural range of foliage color from bluish to deep green. I have some plants in full sun and some in light shade and they are all covered in blooms. Selections and Hybrids Sarita™ A selection of Calliandra californica was made and a patent was filed in 2008 and approved in 2009. It was the result of a mutant seedling that had a strongly prostrate habit. The trademarked name is Sarita™ and also referred to as Calliandra 'Cascada Desiertica’ (not a misspelling). The plant height is listed as 30 cm and width 1.5 meters, so about 12 inches tall and 5 feet wide. The selection was made by Sarah Celestian working at Desert Tree Farm in Phoenix, Arizona.
Sierra Star® Calliandra x Sierra Star® PP15387 is an especially floriferous hybrid between Calliandra californica and Calliandra eriophylla made in 1982 by Ron Gass of Mountain States Nursery. It is also referred to by the variety name of 'Lianca.' It is said to be slow growing, but worth the wait (Figure 6). I don't know about you, but this plant is just lovely, and I can see installing it in many places where turf used to exist. Just perfect with boulders beside a dry stream bed! I can see it mixed with blue agaves, Opuntia basilaris, Encelia farinosa, and a 'Desert Museum' Palo verde. Because of the Calliandra eriophylla influence it is lower growing, at around 4 feet high and wide, and suitable for more garden situations than straight Calliandra californica. What is notable about the cross is the bright red stamens of Calliandra californica have been retained. The plant is deciduous below 30 degrees F and said to be hardy down to 15 degrees F. My references claim that Sierra Star® is more cold tolerant than Maricopa Red®.
Maricopa Red® Calliandra x Maricopa Red® is another cross between Calliandra californica and Calliandra eriophylla (Figure 7). The hybrid was made by Civano Nursery of Tucson, Arizona. From what I have read, this hybrid is slightly shorter than Sierra Star®. The blooms of Maricopa Red® are also pinker than Sierra Star®. Wildlife Value This is always my favorite part; when I get to write about the wildlife you will attract with these plants. It makes me absolutely giddy with anticipation! My plants are favored by hummingbirds (of course!), and unlike many red blooms, are also heavily visited by honeybees, Apis mellifera (Figure 3). Hummingbirds favor these plants over hummingbird feeders since they are high in sucrose with 22-26% concentrations. I also see occasional Monarch butterflies on the blooms. Investigation into other reports find that the plants are also pollinated by flies, additional species of butterflies, like the Marine Blue, Inchworm and Owlet moths, and Carpenter bees (Xylocopa species.) Biologist, Jeffrey Allen Caldwell in his publication, "California Plants as Resources for Lepidoptera: A Guide for Gardeners, Restorationists, and Naturalists" reports that Cloudless Sulphur, Southern Dogface, Monarch, Ceraunus Blue, and Marine Blue all nectar on Calliandra californica. It is also a host plant for Ceraunus Blue and the favored host plant for Marine Blue butterflies. Jeffrey reports that Calliandra eriophylla is visited for nectar by Swallowtail species, and other large butterflies, Imperial Checkerspot (B. J. Stacey), Mormon Metalmark (B. J. Stacey), and Fiery Skipper. Studies show that the flowers are heavy nectar producers. This is probably why I see Argentine ants all over the blooms (grrrr). The pollen is transferred to other flowers by pollen packets, called polyads, that stick to pollinators on their way to another bloom. Each pollen packet is a composite made of at least eight asymmetrical pollen grains. An example of a Calliandra species polyad is in Figure 8 it is from Calliandra bahiana var. bahiana from Brazil. One study of moths found Calliandra pollen was mainly found on moth proboscis and also on eyes, legs and antennae. Bats also feed on Calliandra species. The seeds of the plants are eaten by several species of quail: Gamble's, Bobwhite, Scaled and Mearn's. Other small birds will feed on the abundant nectar such as warblers, finches, verdins, wrens, orioles, and gnatcatchers. The Calliandra species discussed are unarmed and browsed by deer and other mammals. The dense twiggy growth offers a cover source for small animals and a nursery for baby plants. So, in addition to looking awesome in the garden, this plant feeds lots of creatures!
Ethnobotany The studies that I have read list that Calliandra californica has been valuable for resolving urological problems, and possibly as a diabetes treatment, specifically because it contains diterpenes called Escobarine A and Escobarine B. One study found they have antibacterial properties. Another study finds the diterpenes have antituberculosis and cytotoxic activities. Escobarine A specifically displays anti-cancer activity. Historically, the roots of Calliandra californica were used to dye leather red. Decoctions were used in folk medicine to treat cystitis, kidney ache, urethritis, prostate inflammation, cramps, fever, and toothache.
Propagation Both species readily cross. You might want to be aware of this when you see seedlings. I have not actually propagated this particular genus, BUT I have propagated many plants from seed and cuttings and can tell by published propagation techniques what may work and what probably won't. My intuition is pretty good. Working from several sources, I have boiled it down to the following information: The plants propagate easily from seed, but not easily after germination. Keep in mind how explosively and unexpectedly the seed pods open and expel seeds and use small drawstring cloth bags that can be tied around the maturing seed pods to capture the rocketing seeds.
As for the problem with rot, this can be addressed with a combination of modification of methods.
1) Improve soil media so it naturally combats pathogenic fungus, by inoculating it with organic compost and mycorrhizal fungi.
2) Improve air circulation by placing pots outside or under fans.
3) Bottom heat or waiting until it is warmer in the year will decrease the possibility of rot. 4) Plant directly into potting media and bypass a sterile seed starting mix. I worked for a while propagating plants and really thought about the soil mix. I don't believe sterility is good in every circumstance because once a pathogenic fungus floats into the greenhouse from outside, and it always does, there is nothing in the soil to combat it. You are essentially starting seeds in dead soil when it is sterile. Now this may fly in the face of how propagation is normally done, and certainly sterility is required in some situations, but I also believe in the power of biodiversity to solve problems. Additionally, studies have shown improved root growth in soils with good microbiota. Trish Meyer from Wildscaping suggests the following soil recipe: * SunGro's Sunshine #4 soilless mix (fast-draining, comes with fertilizer mixed in, reasonably priced by the bale) * Time-release fertilizer * Organic transplanting fertilizer with mycorrhizal beneficial fungi (EB Stone Sure Start) * A dollop of home-grown organic compost Maybe someday I will try it, but my best guess on how to propagate this plant is to capture the seeds in cloth bags, plant in late spring or summer, plant in deep small pots (rose pots), place outside. You could also try using bottom heat and fans in the greenhouse. Other protocols have mentioned nicking the seed coat or scarification which couldn't hurt but may be overkill. They also mention tip cuttings with IBA as a potential propagation technique, and layering using flexible stems.