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''Xylococcus'' is a
monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...
genus of flowering plants in the heather family which contains the single species ''Xylococcus bicolor'', commonly known as the mission manzanita. It is a
burl A burl (American English) or burr (British English) is a tree growth in which the grain has grown in a deformed manner. It is commonly found in the form of a rounded outgrowth on a tree trunk or branch that is filled with small knots from do ...
-forming,
evergreen In botany, an evergreen is a plant which has foliage that remains green and functional through more than one growing season. This also pertains to plants that retain their foliage only in warm climates, and contrasts with deciduous plants, which ...
shrub to tree with leathery leaves and smooth dark reddish bark. From December to February, white to pink urn-shaped flowers adorn the foliage, often attracting hummingbird pollinators. It is native to
southern California Southern California (commonly shortened to SoCal) is a geographic and cultural region that generally comprises the southern portion of the U.S. state of California. It includes the Los Angeles metropolitan area, the second most populous urban ...
and the Baja California Peninsula, south to the Sierra de la Giganta. There is growing concern over the future of this plant, referred to as the "queen of the
elfin forest Dwarf forest, elfin forest, or pygmy forest is an uncommon ecosystem featuring miniature trees, inhabited by small species of fauna such as rodents and lizards. They are usually located at high elevations, under conditions of sufficient air humi ...
, " as it may possibly lose up to 88% of its habitat and its wild seedlings are failing to survive more than a full year.Gordon, L., R. W. Halsey, J. E. Keeley, J. P. Rebman, D. Wiens and A. Johanson. (2015) Mission manzanita, queen of the elfin forest: is the species in decline? ''Fremontia'' 43(2), 23-28. Known to and utilized by the indigenous peoples for centuries, this species was first described to Western science by
Thomas Nuttall Thomas Nuttall (5 January 1786 – 10 September 1859) was an English botanist and zoologist who lived and worked in America from 1808 until 1841. Nuttall was born in the village of Long Preston, near Settle in the West Riding of Yorkshire ...
, who had found it on his journey to California. Nuttall named it ''Xylococcus'', which is derived from the Greek word for "wood berry." Later botanists lumped this species into the true manzanitas (''
Arctostaphylos ''Arctostaphylos'' (; from "bear" and "bunch of grapes") is a genus of plants comprising the manzanitas () and bearberries. They are shrubs or small trees. There are about 60 species, of ''Arctostaphylos'', ranging from ground-hugging a ...
''), but it has distinct features, such as the flowers and fruit, that support its generic placement. In light of its struggle in the wild, this plant is available from specialty nurseries focusing on
California native plants California native plants are plants that existed in California prior to the arrival of European explorers and colonists in the late 18th century. California includes parts of at least three phytochoria. The largest is the California Floristic ...
, making it a distinctive and hardy shrub in the garden.


Description

Starting from the ground up, one will notice this evergreen shrub or tree has a burl, or lignotuber, an underground storage organ, which is topped by a smooth trunk with peeling red bark. The smooth red trunk is characteristic of other Arbutoideae in the region, like ''
Arctostaphylos ''Arctostaphylos'' (; from "bear" and "bunch of grapes") is a genus of plants comprising the manzanitas () and bearberries. They are shrubs or small trees. There are about 60 species, of ''Arctostaphylos'', ranging from ground-hugging a ...
'' species, although this species has a darker tint to its bark. This species may rarely grow up to in height. The stems are erect, generally less than in length, with canescent twigs. On the twigs are the alternately-arranged, leathery leaves, which have a lower surface that is densely covered with white to gray hairs. The margin of the leaves lack teeth and are rolled under. The leaves are up to 4.5 cm long. The dense inflorescence is a
panicle A panicle is a much-branched inflorescence. (softcover ). Some authors distinguish it from a compound spike inflorescence, by requiring that the flowers (and fruit In botany, a fruit is the seed-bearing structure in flowering plants that is ...
, which hangs downward and is bracted. The pedicel is not jointed to the flower, with 2 bractlets. There are 5
sepal A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 The term ''sepalum'' was coined ...
s on the flower, along with 5
petal Petals are modified leaves that surround the reproductive parts of flowers. They are often brightly colored or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corolla''. Petals are usuall ...
s, which are fused to form an urn-shaped corolla. The white to pink corolla is covered in hairs. Within the flower, there are 10
stamen The stamen (plural ''stamina'' or ''stamens'') is the pollen-producing reproductive organ of a flower. Collectively the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filam ...
s, with the filaments wooly in their lower half. The
ovary The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the bod ...
is superior (attached to the receptacle above the attachment of other floral parts) and is hairy, with generally 5 chambers. Upon maturity, the flowers turn into a fruit around wide. The fruit is a dark-brown
drupe In botany, a drupe (or stone fruit) is an indehiscent fruit in which an outer fleshy part ( exocarp, or skin, and mesocarp, or flesh) surrounds a single shell (the ''pit'', ''stone'', or '' pyrena'') of hardened endocarp with a seed (''kerne ...
, with 5 stones that are fused into a smooth unit.


Etymology

The name ''Xylococcus'' derives from the Greek word for "wood berry," which refers to the rock-hard stone the seeds are encased within. The specific epithet, ''bicolor'', refers to the leaves, which are a dark green on the top surface and a wooly-white on the bottom.


Distribution and habitat

The plant's native range is very limited, to the Peninsular Ranges in
Southern California Southern California (commonly shortened to SoCal) is a geographic and cultural region that generally comprises the southern portion of the U.S. state of California. It includes the Los Angeles metropolitan area, the second most populous urban ...
(U.S.) and the Baja California Peninsula (México), the South Coast of
California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the ...
and Santa Catalina Island, and the northwestern
Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...
coast and
Cedros Island Cedros Island (''Isla de Cedros'', "island of cedars" in Spanish (language), Spanish) is an island in the Pacific Ocean belonging to the state of Baja California, Mexico. The dry and rocky island had a population of 1,350 in 2005 and has an area ...
.Jepson: "Xylococcus bicolor"
/ref> Its populations are primarily in
San Diego County, California San Diego County (), officially the County of San Diego, is a county in the southwestern corner of the U.S. state of California. As of the 2020 census, the population was 3,298,634, making it California's second-most populous county and the f ...
and Baja California state. It is a member of the
chaparral Chaparral ( ) is a shrubland plant community and geographical feature found primarily in the U.S. state of California, in southern Oregon, and in the northern portion of the Baja California Peninsula in Mexico. It is shaped by a Mediterrane ...
plant community, in the
California chaparral and woodlands The California chaparral and woodlands is a terrestrial ecoregion of southwestern Oregon, northern, central, and southern California ( United States) and northwestern Baja California ( Mexico), located on the west coast of North America. It ...
and
California coastal sage and chaparral ecoregion The California coastal sage and chaparral ( es, Salvia y chaparral costero de California) is a Mediterranean forests, woodlands, and scrub ecoregion located in southwestern California (United States) and northwestern Baja California (Mexico). It i ...
s. It grows at elevations below , on dry, sunny slopes. In Baja California, the species also occurs outside of the chaparral plant community, particularly in sky islands of the Central Desert, and in the xeric scrub community of the Sierra de la Giganta mountain ranges in
Baja California Sur Baja California Sur (; 'South Lower California'), officially the Free and Sovereign State of Baja California Sur ( es, Estado Libre y Soberano de Baja California Sur), is the least populated state and the 31st admitted state of the 32 federal ent ...
.


Ecology

Birds, including the California thrasher and scrub jay, eat its seeds. Hummingbirds, especially the resident Anna's hummingbird, drink nectar from its flowers. Various birds nest in the plant, and many use it for cover. While some
chaparral Chaparral ( ) is a shrubland plant community and geographical feature found primarily in the U.S. state of California, in southern Oregon, and in the northern portion of the Baja California Peninsula in Mexico. It is shaped by a Mediterrane ...
plant species require
fire Fire is the rapid oxidation of a material (the fuel) in the exothermic chemical process of combustion, releasing heat, light, and various reaction Product (chemistry), products. At a certain point in the combustion reaction, called the ignition ...
to germinate seeds and reproduce, ''Xylococcus bicolor'' does not, nor does it require openings left by wildfires. As a
chaparral Chaparral ( ) is a shrubland plant community and geographical feature found primarily in the U.S. state of California, in southern Oregon, and in the northern portion of the Baja California Peninsula in Mexico. It is shaped by a Mediterrane ...
member species it must have a means of coping with wildfire, and it does so by resprouting from the base after its top has burned away. This mechanism works very well, unless a second fire follows closely after the first. If a plant has not had time to sufficiently regenerate, it will probably perish.


Reproductive crisis

There is growing concern that this species is unable to produce young individuals in the wild. Despite producing thousands of
drupe In botany, a drupe (or stone fruit) is an indehiscent fruit in which an outer fleshy part ( exocarp, or skin, and mesocarp, or flesh) surrounds a single shell (the ''pit'', ''stone'', or '' pyrena'') of hardened endocarp with a seed (''kerne ...
s annually, many intensive searches had failed to find seedlings, and it was believed that the species could no longer reproduce by seeds. Complicating this predicament, the seeds of ''Xylococcus'' are still perfectly viable, with 61% of stones having at least one seed filled with live endosperm. One hypothesis put forward was that the seeds needed to pass through the digestive system of the now-extinct
California grizzly bear The California grizzly bear (''Ursus arctos californicus'') is an extinct population or subspecies of the brown bear, generally known (together with other North American brown bear populations) as the grizzly bear. "Grizzly" could have meant "gri ...
to germinate, or that the stones containing the seeds need to be broken by the bear's strong jaws. Some experts, like Paul Zedler at the University of Wisconsin-Madison, contend that ''Xylococcus'' reproduction might simply encompass a larger timeframe than human observers might expect, similar to the long reproductive cycles in species like the giant sequoia, '' Sequoiadendron gigantea''. The giant sequoia annually produces 300,000 to 400,000 seeds, with many seedlings emerging from the duff on the forest floor, but only very few of these seedlings thrive unless conditions are correct. This means that despite the massive seed production, the giant sequoia seldom has young plants that can maintain the density of old groves. Some specimens of ''Xylococcus'' can live up to a century or more, and like the giant sequoia, produce thousands of their seeds annually through their drupes, meaning that perhaps their reproduction occurs on a longer ecological time scale. In 2008, a bioblitz in
San Diego San Diego ( , ; ) is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the eighth most populous city in the United States ...
led to the discovery of 53 seedlings and possible saplings growing in Florida Canyon, Balboa Park. It was discovered that the following February, none of the 2008 seedlings had survived, although new ones had emerged, meaning that none of the seedlings could survive a full year. Many other seedlings have been found successfully growing, but they are difficult to monitor, and often in the path of development. Very few seedlings have been documented to survive more than year, although one 30-year old seedling has been found.


Uses

The Native American Luiseño people bruised ripe berries and soaked them overnight in cold water to produce a cider-like drink.
Delfina Cuero Delfina Cuero (ca 1900 – 1972) was a Native American writer of the Kumeyaay people. The daughter of Vincente Cuero and Cidilda Quaha, she was born in Xamca (later known as Jamacha). The Kumeyaay people, whose traditional lands straddle the M ...
, a member of the
Kumeyaay The Kumeyaay, also known as Tipai-Ipai or by their historical Spanish name Diegueño, is a tribe of Indigenous peoples of the Americas who live at the northern border of Baja California in Mexico and the southern border of California in the Unit ...
people, corroborates a similar use of ''Xylococcus'' (known to her people as ''Haasill''), soaking the ripe berries to use as a cool drink.


Cultivation

''Xylococcus bicolor'' is cultivated as an
ornamental plant Ornamental plants or garden plants are plants that are primarily grown for their beauty but also for qualities such as scent or how they shape physical space. Many flowering plants and garden varieties tend to be specially bred cultivars that ...
by specialty
plant Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all curr ...
nurseries, for planting in California native plant and wildlife gardens. It forms an interesting shrub with flowers that hummingbirds like. It prefers to have its leaves in full sun, but likes its roots in the shade. This species is tolerant of most soils, but requires excellent drainage. It needs fast draining soil of pH 6–7, in USDA zones 7–10. This plant is best suited on north-facing, dry rocky slopes. It grows at a moderate pace in a rounded shape, usually about high by wide. It prefers regular light watering over the first summer after planting. After establishment, this drought-tolerant shrub should survive the dry months with no supplemental water, though it can usually handle summer watering infrequently. It provides white and pink blooms over winter and spring, and is hardy down to 20 °F during these months.


Propagation

This species is notoriously difficult to propagate, and wild seedlings are seldom to survive past a year. Wild seeds are viable, and can be grown successfully provided proper protocols are followed. The fleshy outer layer of the fruit first must be removed, with some putting the fruits with water in a blender to remove the outer layer. Stones are then removed from the blender, and broken open with wire cutters. As the stones are brittle, around half of the seeds can be released undamaged. Seeds that are damaged in this process can be soaked in 0.3% hydrogen peroxide and copper soap to curb pathogens. Seeds may also be soaked in water to improve germination. However, they germinate best when stratified at 55 °F, often accomplished by placing them in a refrigerator. The treated seeds are placed in a food container on top of fine, moist potting soil, and within two weeks, around half of the seeds will have radicles emerging. Once these radicles emerge, it is recommended to place the seeds into pots, in a soil mix with extra perlite to improve drainage. The delicate plantlets need shade and periodic misting in this period. Eventually, cotyledons will emerge within fibrous sheaths. When the sheaths fall off and release the cotyledons, misting may be stopped, but shade is still required for root development.


Gallery

File:Old-growth mission manzanita in San Diego County, California.jpg, The trunk of an old-growth ''Xylococcus'' in San Diego County File:Xylococcus bicolor 900 45.jpg, A view of the whole plant File:J20161123-0059—Xylococcus bicolor—RPBG—DxO (30540577264).jpg, Flowers and flower buds File:J20151209-0043—Xylococcus bicolor—RPBG (23363556749).jpg, The drupes File:MissionManzanitaBlooming03-P.jpg, In bloom with old fruit File:Xylococcus bicolor 116910873.jpg, The young fruits


See also

* '' Ornithostaphylos'' – Another monotypic Arbutoideae genus in the same region * ''
Cneoridium ''Cneoridium'' is a monotypic genus in the citrus family which contains the single species ''Cneoridium dumosum'', commonly known as bushrue or coast spice bush. This perennial, evergreen shrub is native to the coast of southern California and B ...
'' – An unrelated (also monotypic) shrub in the same region that also has dark, spherical berries * '' Sideroxylon grandiflorum –'' A drupaceous tree that was (erroneously) believed to have lost its reproductive capabilities due to the extinction of the dodo. * '' Cercocarpus traskiae'' ''–'' Another shrub native to California that may go extinct because of the failure of seedlings to survive.


References

*James Lightner ''San Diego County Native Plants'', San Diego Flora (2004)


External links


CalFlora Database: ''Xylococcus bicolor'' (mission manzanita)Jepson's "A Flora of California"Jepson Flora Project (TJM93) treatment of "Xylococcus bicolor"

Jepson eFlora (JM2) treatment of "Xylococcus bicolor"Photos of ''Xylococcus bicolor''
{{Taxonbar, from1=Q3488329, from2=Q17372400 Arbutoideae Flora of California Flora of Baja California Flora of Baja California Sur Plants described in 1842 Garden plants of North America Drought-tolerant plants Taxa named by Thomas Nuttall