Styrax

Here too grow some specimens of Styrax officinale of which the Foundation is particularly proud. For this plant is referred to in ancient documents and is depicted on the fine mosaic of the terrestrial paradise at Heracleia Lynchestis: it grows wild in Rhodes yet is unknown to nurserymen, and we succeeded in propagating it from seed collected in the woods!

Manuela de Montalembert, The Renaissance of a Garden in Rhodes,
The Mediterranean Garden

Styrax redivivus on Walker Ridge, Colusa County, California, with toyon (Heteromeles californica) to the left and foothill pine (Pinus sabiniana) in the background. Author’s photographs

Styrax redivivus on Walker Ridge, Colusa County, California, with toyon (Heteromeles californica) to the left and foothill pine (Pinus sabiniana) in the background. Author’s photographs

Imagine a native shrub that produces an *abundance of waxy white blossoms, is readily propagated, long-lived, and tolerant of a wide range of conditions from full sun to bright shade and of drought or regular water. Yet, it is virtually unknown. Its two fatal flaws—slow growth and deciduous foliage—would certainly limit its mass popularity in California horticulture, but seem insufficient justification for the obscurity of California styrax.

Worldwide, there are about 130 species of Styrax with the greatest concentration in Southeast Asia. The Jepson Manual lists our native California styrax as Styrax officinalis var. redivivus. The same species name (S. officinalis) is given to the styrax that is native to the Mediterranean from southern Greece to Turkey, south to Israel, and naturalized at an early date in Italy and southern Spain. Treating the two populations as one species on different continents, without it occurring between, is remarkable given the great distance involved (nine time zones). This separation is even more remarkable given that the species has no innate dispersal mechanisms and has unknown and apparently rather indifferent animal vectors for dispersal. The most common dispersal mechanism seems to involve the seed either rolling downhill or floating downstream. Treated as one species, the Californian and Mediterranean styraxes played a role in theoretical models of ancient plant dispersal routes over hypothetical Tertiary landmasses—the supercontinent Laurasia, which combined Europe, much of Asia, and North America.

The nineteenth-century American botanist John Torrey originally gave the name Darlingtonia rediviva to California styrax in 1851; in 1853, he renamed it Styrax californica after obtaining good flowering material and correctly perceiving its true genus. (He later recycled the name Darlingtonia, in honor of another American botanist, for a then new genus of pitcher plant, found in Northern California and Oregon.)

Since the first worldwide taxonomic treatment of the genus Styrax by Janet Perkins in 1907, most authors have lumped our California species with the Mediterranean shrub. Perkins could find no significant difference between the California and Mediterranean material. Working with pressed herbarium specimens, she missed critical differences that become apparent in the field. Recently, extensive research on numerous fronts by scientist Peter Fritsch, associate curator for the Department of Botany at the California Academy of Sciences, has provided strong justification for recognizing our native as a distinct species, called Styrax redivivus. This distinction is true regardless of whether a biological, phylogenetic, or taxonomic species concept is employed.

Fritsch summed it up as follows:

My primary research focuses on the systematics, biogeography, and evolution of members of the woody flowering plant order Ebenales, a group that includes the snowdrops (Styrax), silverbells (Halesia), persimmons and ebonies (Diospyros). Many of the plants in this order are disjunct relicts, which means that they were once (in the Miocene) widespread but are now restricted in range to discrete and widely separated areas of the earth, due to climate change. These areas include California, the rim of the Mediterranean Basin, eastern North America, and eastern Asia. I use a combination of morphological and molecular approaches on these groups to understand their species diversity, evolutionary relationships, and adaptations to particular environments. The patterns of relictualism and speciation elucidated from these studies can eventually lead to a better overall understanding of the effects and significance of climate change on the world’s biota.

Regarding the California native styrax’s relationship to the Mediterranean Styrax officinalis:

The bottom line is that Styrax is a genus of about 130 species, two sections, and two series within each section. Californian styrax (one species: Styrax redivivus) falls into series Styrax of section Styrax. In series Styrax there are only three species: S. redivivus, S.
platanifolius
from Texas and Northern Mexico, and S. officinalis from the Mediterranean region. It turns out that the closest relative of S. redivivus is S. platanifolius, and S. officinalis is the closest relative of the group composed of S. redivivus and S. platanifolius. In other words, S. redivivus and S. officinalis are close relatives, but not each other’s closest relative. (It’s all derived from the “new” phylogenetic way of thinking about evolution and plant relationships.)

In 1996, Fritsch wrote that . . . Styrax redivivus and S. officinalis have probably been separated intercontinentally for at least five million years. Still, the California and Mediterranean species share some interesting qualities: they both occur under a mediterranean climate. From my data, I have concluded that, although the adaptations to dry climates that these two species share were probably in existence in their common ancestor, their adaptation to mediterranean climates, in particular, are probably independent events. (This is because mediterranean climates are quite recent, and S. platanifolius, the closest relative of S. redivivus, occurs in areas of summer rain, the “primitive” kind of habitat.)

Nomenclature and Description

In California, Styrax redivivus has been given the common name of snowdrop bush. I assume this is because the white flowers drop more or less simultaneously, creating a lovely skirt of waxy snow-white blossoms, on the ground around the base of the shrub, which persists for several days. The California Academy of Science website states “The name snowdrop refers to the snow white, nut-like fruit and not to the color of the flower.” This may be referring to the fruit of the Mediterranean S. officinalis, which, according to Polunin and Huxley in Flowers of the Mediterranean, bears “fruit the size of a cherry and covered with a white felt.” With regard to our native species, however, this explanation seems unlikely, as the exterior seed coat is green, turning tan or gray brown. Bitternut is another common name given to the shrub, for obvious reasons.

The swollen base of Styrax redivivus,  a survival strategy in fire-prone regions

The swollen base of Styrax redivivus, a survival strategy in fire-prone regions

The species epithet, redivivus, presumably refers to our native’s ability to spring back to life after fire or severe pruning. The base of the plant forms a swollen growth from which it resprouts, similar in appearance and function to the basal burl of fire-adapted manzanitas, such as Arctostaphylos glandulosa.

Linnaeus described Styrax officinalis in the 1750s from plants that were known to him in the wild. The common name for the European species is storax, a Greek name given by Theophrastus, the “Father of Medicine,” to a plant providing the gum they called storax, although that plant may or may not have been the one we now know as Styrax officinalis. Many Styrax species do produce medicinal resins. Gum from the Mediterranean styrax is still used in the Roman Catholic Church for incense and perfumes; the seeds are used to make rosaries. However, the resin known as liquid storax is from an unrelated tree (Liquidambar orientalis) of the Turkish Mediterranean coast.

The flowers of the European Styrax officinalis are reputed to resemble orange blossoms in both appearance and fragrance, and I’ve seen references to a fragrance for our California native Styrax. Arthur Gibson, director of UCLA’s Mildred E Mathias Botanic Garden, noted that “the strong, sweet fragrance, white design, and exserted style and stigma all suggest that this plant is adapted to hawkmoth pollination.” I recently detected a faint citrus fragrance on plants in the wild at Walker Ridge, but the cultivated shrubs I am familiar with, from both northern and southern California populations, have little or no detectable fragrance where I grow them in Sonoma County.

I have not seen hawkmoths pollinating styrax, but I have observed honeybees and native bees actively foraging for floral nectar on wild and cultivated plants of Styrax redivivus. On our Fulton, California, nursery plant, now twenty years old and ten feet tall and wide, I have observed tiger and pipevine swallowtail butterflies feeding on the nectar and discouraging other butterfly species.

I have personally encountered our native styrax only three times in the wild in California, first in the hills above Santa Barbara, where it was a member of the chaparral community. There it grew as a shrub in the open, in the full Southern California sun amongst huge sandstone boulders. On another occasion, I encountered it near Feather Falls in Butte County, where it was growing as a lone small tree in the shade of a high coniferous-forest canopy. Most recently, I have observed it in mixed chaparral on the flank of Walker Ridge just above Bear Valley in Northern California’s Colusa County. There it grows on a north-facing slope in
serpentine-derived soil, associated with toyon (Heteromeles californica) and foothill pine (Pinus sabiniana).

Styrax officinalis is reported often to grow on limestone in the Mediterranean, as does its close relative S. platanifolius in Texas and northern Mexico. This, along with the occasional preference of S. redivivus for serpentine, might suggest that these are all examples of relict species surviving on soils that are relatively demanding or inhospitable to their competition.

Flowers and foliage of Styrax redivivus

Flowers and foliage of Styrax redivivus

Cultivation and Placement

Styrax redivivus is graceful and arching with an angular twiggy growth pattern; it is likely to respond to hard pruning with long whip-like growth. Its leaves are thin, round and handsome, rather widely spaced on the branches. This, combined with its form, creates an open “see-through” plant, a quality I find attractive and useful in the garden.

Observing the environmental conditions under which a plant grows in nature can be a key to choosing its proper treatment and placement in the garden. Given the range of recorded habitats for styrax in the wild—from full sun in Southern California to forest understory or chaparral and serpentine-derived soils in Northern California—what is one to think?

In the garden, they certainly need good drainage and seem tolerant of a wide range of soils and drought, but they accept and appreciate occasional deep watering. Styrax redivivus, perhaps especially those from Northern California, seems tolerant of bright shade, although plants in full sun bloom more prolifically. Our twenty-year-old specimen in Fulton is situated in bright shade in rich, dark, heavy adobe soil. At my home in Sebastopol, this styrax has been happy in either bright shade or full sun in the lean and sandy native soil. I would suggest that it generally prefers sun and only tolerates shade, and that it resents too much coastal influence.

Dave Fross, of Native Sons Nursery in Arroyo Grande, reports occasionally growing Styrax redivivus, but experiences difficulty in selling the plants. “Although I’m quite fond of it, I haven’t managed to establish a plant in my garden (partial shade, sandy soil, coastal, dry.) Plants at the Santa Barbara Botanic Garden are stunning (coastal canyon, partial shade, alluvial soil, dry).” He agrees that it is slow growing.

Bart O’Brien, horticulturist at Rancho Santa Ana Botanic Garden notes that Styrax redivivus . . . is also native to the extremely hot, south-facing slope of the San Bernardino Mountains in the City Creek drainage—not in the riparian areas, but on fully exposed, hot, dry, steep granitic slopes, with Arctostaphylos glandulosa subsp. glaucomollis, a few A. pringlei subsp. drupacea, and scattered Pinus attenuata.

Here at RSA, the best specimens are planted at the north end of the mesa (dense clay-loam soil that holds moisture well). These plants are mostly in dappled sunlight due to nearby pines, oaks, and maples. They are about fifty years old and vary in height from about six to twelve feet tall. Ours do not spread too wide, but are definitely multi-trunked and shrub-like. Periodically the largest stems have been removed and this seems to keep the plants growing vigorously. They bloom well here and last from one to three or more weeks in April and May, depending upon the weather. They do not seem to have any pests or diseases.

Fritsch added some observations on propagation:

I did a lot of Styrax redivivus germination during my dissertation, and cold-stratification in moist vermiculite in a sealed zip-locked bag for three to four months worked well. . . . As I understand it, the seeds can dry out over a short period of time after ripening, so I put them into cold-stratification a short time (within two weeks?) after I picked them.


The author wishes to acknowledge the generous help provided by Peter Fritsch in the preparation of this article.