Buckthorn Family (Rhamnaceae). Mountain whitethorn is a densely branched, spiny, evergreen, flat-topped native shrub, which reaches heights of 2 to 5 feet. However, at elevations, such as the Lake Tahoe Basin, it assumes a low spreading growth form. Individual plants may spread to form continuous ground cover over areas with a diameter up to 12 feet. The numerous stems terminate in a hard sharp point thus, the name whitethorn.
Whitethorn flowers form in a small, dense cluster 1 to 2 inches long. The flowers, which bloom from late spring to mid summer, have a heavy penetrating fragrance. During the flowering season, the abundant white flowers may cause areas to appear covered with snow.
Regularity: Regularly occurring
Whitethorn ceanothus is a characteristic shrub species found in high-elevation brushfields in Baja, California, and mountains of southern California, north to southwest Oregon, and east to the western edge of Nevada [23,27,36,56]. Plants Database provides a distributional map of whitethorn ceanothus.
States or Provinces
Regional Distribution in the Western United States
This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):
BLM PHYSIOGRAPHIC REGIONS :
3 Southern Pacific Border
4 Sierra Mountains
Mountain whitethorn is well suited to dry open flats and rocky slopes with well-drained soils.
California, Nevada, and Southwest Oregon. For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site.
Whitethorn ceanothus is a native, evergreen shrub. It has a low-lying, flat-topped growth habit, especially at higher elevations, and generally reaches heights between 2 and 5 feet (0.6-1.5 m). Whitethorn ceanothus can form a continuous ground cover up to 12 feet (3.7 m) in diameter. The many short, rigid, intricately-branched stalks end in sharp spines. The numerous leaves are alternate and distinctly 3-ribbed from the base. They are small, elliptic to egg-shaped, and blunt at the tip. The leaf margins are entire or finely toothed. Flowers are in dense clusters borne on a panicle-like inflorescence. The fruit is a capsule that is slightly crested or horned and somewhat sticky at maturity. It is small, tipped by a threadlike 3-forked appendage, and 3-lobed. Each lobe has a ridge on its back and is 3-celled with each cell bearing 1 hard, round seed or nutlet. [13,25,26,47,73,74, 78,98]
Whitethorn ceanothus has high nitrogen concentrations in its foliage and soil beneath the plant due to the nitrogen-fixing bacteria Frankia spp., suggesting that it may enhance nitrogen availability for the surrounding area [75,76].
Key Plant Community Associations
Whitethorn ceanothus has a narrow range of environments in which it thrives. It is most commonly
found within sclerophyllous shrub communities in both conifer and hardwood forests of the coast
and interior ranges of the Sierra Nevada [13,31]. In addition to the previously listed habitats,
whitethorn ceanothus also occurs in the understory of giant sequoia (Sequoiadendron giganteum)
communities/groves because of its ability to tolerate low light levels [17,45,104].
Whitethorn ceanothus is not an indicator species for any specific habitat types, but is listed as
a "moderate site indicator" in forested communities of the upper montane in the southern
and central Sierra Nevada .
Other overstory species commonly associated with whitethorn ceanothus are California black oak (Quercus
kelloggii), bitter cherry (Prunus emarginata), and Brewer oak (Q. garryana var. breweri).
Common understory associates of whitethorn ceanothus include: huckleberry oak (Q. vacciniifolia),
bush chinquapin (Chrysolepis sempervirens), pinemat manzanita (Arctostaphylos nevadensis),
greenleaf manzanita (A. patula), creeping snowberry (Symphoricarpos mollis), redflower currant
(Ribes sanguineum), Sierra gooseberry (R. roezlii), California hazel (Corylus cornuta var.
californica), deerbrush (Ceanothus integerrimus), prostrate ceanothus (C. prostratus),
snowbrush ceanothus (C. velutinus), Sierra mountain misery (Chamaebatia foliolosa), salal
(Gaultheria shallon), Pacific rhododendron (Rhododendron macrophyllum), and Saskatoon serviceberry
(Amelanchier alnifolia) [21,24,52,60,63,69,98].
Habitat: Rangeland Cover Types
This species is known to occur in association with the following Rangeland Cover Types (as classified by the Society for Range Management, SRM):
More info for the term: cover
SRM (RANGELAND) COVER TYPES :
209 Montane shrubland
Habitat: Cover Types
This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):
More info for the term: cover
SAF COVER TYPES :
207 Red fir
210 Interior Douglas-fir
211 White fir
218 Lodgepole pine
219 Limber pine
234 Douglas-fir-tanoak-Pacific madrone
237 Interior ponderosa pine
243 Sierra Nevada mixed conifer
244 Pacific ponderosa pine-Douglas-fir
245 Pacific ponderosa pine
246 California black oak
247 Jeffrey pine
249 Canyon live oak
256 California mixed subalpine
Habitat: Plant Associations
This species is known to occur in association with the following plant community types (as classified by Küchler 1964):
More info for the term: shrub
KUCHLER  PLANT ASSOCIATIONS:
K005 Mixed conifer forest
K007 Red fir forest
K008 Lodgepole pine-subalpine forest
K010 Ponderosa shrub forest
K018 Pine-Douglas-fir forest
K020 Spruce-fir-Douglas-fir forest
K023 Juniper-pinyon woodland
K029 California mixed evergreen forest
K034 Montane chaparral
This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):
FRES21 Ponderosa pine
FRES26 Lodgepole pine
FRES34 Chaparral-mountain shrub
Whitethorn ceanothus grows best in open situations [10,17]. Dry, open flats, pine forests, rocky ridges, and washes that have well-drained soils are common sites where whitethorn ceanothus is found [23,47,52,74,98]. Areas that have been burned or logged are very favorable for populations of whitethorn ceanothus [2,27,71]. It can also survive and thrives in the shade of coniferous timber .
Fire Management Considerations
Prescribed burning of whitethorn ceanothus is used in land management to increase browse .
The evolution of whitethorn ceanothus and fire together suggests that the use of prescribed burning is a viable management option in areas to promote whitethorn ceanothus. The use of fire to promote whitethorn ceanothus is suitable because of the fire-stimulated germination of seeds and stump-sprouting in moderate fuel consumption burns. The species adds nitrogen to the soil, possibly enhancing conifer regeneration.
Conversely, overstocked or well-established stands of whitethorn ceanothus add significantly to fuel loading. Extensive stands of whitethorn ceanothus and montane chaparral patches exhibited the greatest mean fire spread/minute and the greatest flame lengths compared to forested types . Snyder  notes that during succession, brush cover is still significant even as the basal area of trees doubles. If these populations persist as noted they could act as ladder fuels, increasing the possibility of a stand replacing fire.
Fuel loading becomes an important factor to recognize when using prescribed fire as a land management tool. The changing fire regime in communities where whitethorn ceanothus becomes established, to infrequent, high-severity fires , suggests that using fire to manage whitethorn ceanothus should be done with caution.
Broad-scale Impacts of Plant Response to Fire
Dormant whitethorn ceanothus seeds in the soil can withstand temperatures up to 220 Â°F (105 ÂºC). This
ability to withstand high soil temperatures is an important survival tool and permits the seeds to
endure long heat exposure during wildland fires and then germinate and occupy burned areas. Seeds
exposed to lethal temperature regimes created by burning heavy accumulations of slash or decaying
logs are destroyed .
Fire removes most of the above ground whitethorn ceanothus biomass, leaving nitrogen-rich, bare mineral
soil. Following fire, patches of whitethorn ceanothus maintain higher amounts of available nitrogen for
up to 6 months on both low- and high-intensity burn plots. If these areas continue to have more available
nitrogen than other patch types, this long-term effect may enhance tree seedling growth .
The Research Project Summary Plant response to prescribed burning with
varying season, weather, and fuel moisture in mixed-conifer forests of
California provides information on prescribed fire and postfire response
of many plant community species including whitethorn ceanothus.
Plant Response to Fire
Whitethorn ceanothus responds favorably to fire. Many soil-stored seeds germinate after fire breaks seed dormancy; seedlings can account for more than half of the plants present in burn areas [34,37]. Whitethorn ceanothus also stump-sprouts after fire . Burned areas stimulate nitrification through the perpetuation of nitrogen-fixing shrubs such as whitethorn ceanothus, accelerating the recycling of nutrients stored in living and dead plants .
Broad-scale Impacts of Fire
A study in mixed conifer ecosystems in the Sierra Nevada, in which whitethorn ceanothus occurred, showed that if duff consumption was 64% or less, few whitethorn ceanothus shrubs were killed and few seeds were stimulated to germinate. The threshold heat load necessary to scarify high numbers of seed stored in the soil bank was very close to the threshold that can kill below ground meristematic tissues of resprouting shrubs. At consumption levels greater than 64% the number of seedlings increased exponentially while survival of resprouters decreased from 94 to 50%. If duff consumption was greater than 94% both are reduced and the heat loads are severe enough to cause a decline in the number of seeds in the soil which survive and successfully germinate . A later study by Kauffman and Martin  done in the same mixed conifer ecosystems of the Sierra Nevada , shows that whitethorn ceanothus was more resistant to fire-induced mortality than other species found in association, such as California black oak and tanoak (Lithocarpus densiflorus). Although there were few or relatively no shrubs present on plots before burning, numbers and frequency of whitethorn ceanothus increased after burning [46,59].
Immediate Effect of Fire
Fire top-kills or kills whitethorn ceanothus, depending on severity . It is resistant to fire-induced mortality because of the deeply buried meristematic tissues .
POSTFIRE REGENERATION STRATEGY :
Tall shrub, adventitious bud/root crown
Ground residual colonizer (on-site, initial community)
Fire adaptations: Whitethorn ceanothus is highly dependent on fire [11,14]. After fire it regenerates by stump-sprouting or from seed depending on the severity of the burn. It is characterized specifically as an obligate sprouter in moderate fuel-consumption burns and a facultative seeder following high fuel-consumption fires [25,54]. The seeds of whitethorn ceanothus are refractory: requiring heat alone or in conjunction with other conditions such as cold stratification . Heat from a burn initiates germination by cracking the seed coat to allow for absorption of water [10,17,38,80,82].
FIRE REGIMES: Whitethorn ceanothus occurs in a mixed fire regime. The presettlement fire regime for communities where whitethorn ceanothus occurs consisted of frequent, low-severity burns and larger stand-replacing fires. Postsettlement, this trend has changed and produced more lethal fires with higher severities and longer intervals . The fire return intervals in the montane chaparral, where whitethorn ceanothus most often occurs, are "probably quite variable" due to the influence of poor growing conditions . Fire in the subalpine forest habitats where whitethorn ceanothus occurs is infrequent due to limited productivity and fuel accumulation in association with short growing season and heavy snow cover .
The following table provides fire return intervals for plant communities and ecosystems where whitethorn ceanothus is important. For further information, see the FEIS review of the dominant species listed below. If you are interested in plant communities or ecosystems that are not listed below, see the complete FEIS Fire Regime Table.
|Community or ecosystem||Dominant species||Fire return interval range (years)|
|California montane chaparral||Ceanothus and/or Arctostaphylos spp.||50-100|
|pinyon-juniper||Pinus-Juniperus spp.||<35 |
|Sierra lodgepole pine*||Pinus contorta var. murrayana||35-200|
|Jeffrey pine||Pinus jeffreyi||5-30|
|Pacific ponderosa pine*||Pinus ponderosa var. ponderosa||1-47 |
|interior ponderosa pine*||Pinus ponderosa var. scopulorum||2-30 [4,5,64]|
|coastal Douglas-fir*||Pseudotsuga menziesii var. menziesii||40-240 [4,72,84]|
|California mixed evergreen||Pseudotsuga menziesii var. menziesii-Lithocarpus densiflorus-Arbutus menziesii||<35|
|canyon live oak||Quercus chrysolepis||4]|
|California black oak||Quercus kelloggii||5-30 |
More info for the terms: succession, tree
Whitethorn ceanothus can be classified as both an early- and late-successional species. It is considered a pioneer species most commonly associated with early successional stages because of its ability to germinate from seed and sprout after disturbance [15,81]. Since whitethorn ceanothus is one of the 1st plants to become established on denuded soils, it has immediate value in soil protection and later serves as a nurse crop for coniferous species . It is possible that whitethorn ceanothus plays an important role in succession by providing a more favorable microclimate of nutrient rich microsites in otherwise harsh growing conditions .
In normal seral conditions whitethorn ceanothus is overtopped and killed by the conifer species that become established in their shade. The brushfields can, however, significantly hinder conifer regeneration and slow the rate of forest succession. If there is repeated fire, whitethorn ceanothus brushfields can become semipermanent communities . Where fire is lacking, it does not establish and populations decrease, and in some cases are eliminated, in the shade of dense tree canopies .
A study by Fernau and others  along the west face of the central Sierra Nevada classified whitethorn ceanothus as a late-successional species, with populations peaking 26-32 years after disturbance. Findings published by Minnich  also provide evidence that it is capable of existing in later successional stages. He states that chronosequences of postsuccession show the establishment of seedlings of whitethorn ceanothus without fire, apparently from seed caches.
Whitethorn ceanothus regenerates by seed and vegetative means. Germination from seeds stored in the soil is the primary mode of reproduction for whitethorn ceanothus and generally takes place after fire [40,54]. Prolific sprouting occurs from a lignotuber when damage is done to the top of the plant [40,50]. Whitethorn ceanothus is an obligate sprouter in moderate fuel-consumption burns and a facultative seeder following high fuel-consumption burns .
Pollination: Whitethorn ceanothus is an insect-pollinated species .
Seed production: Ceanothus spp. are prolific seed producers. Thousands of viable seeds can be produced per hectare and remain dormant in the soil and duff layer until disturbance stimulates germination [38,48]. At approximately 4 years of age, whitethorn ceanothus is capable of seed production and reaches a maximum seed load of approximately 4,500 seeds per plant by the age of 20 to 25. Seed production remains high until the plant is senescent, around 40 years of age, or where the plants are inhibited by shade .
Seed dispersal: Whitethorn ceanothus seeds are autochorus, meaning that the main mode of seed dispersal is by the plant itself . The seeds are small and tend to stay where they fall, unless they are carried off by birds, rodents, or ants [22,67]. Ceanothus seeds can also be forcibly ejected from the seed pods when they ripen [22,55].
Seed banking: Because of the large number of seeds produced by whitethorn ceanothus, substantial seed reservoirs exist in the soil and duff layer. The number of seeds in the soil can be expected to vary from year to year depending on the amount of seeds produced and seeds utilized by consumers . Keeley  notes a relationship between the seed bank size and stand age where whitethorn ceanothus is found; the older the stand the larger the seed bank will be. Seed quantities of whitethorn ceanothus combined with littleleaf ceanothus (Ceanothus parvifolius) in over-mature mixed coniferous forests can number up to 1.9 million/acre .
Germination: Whitethorn ceanothus is heavily dependent upon fire for germination . The seeds of whitethorn ceanothus are refractory: they require a heat stimulus alone or in conjunction with other conditions such as cold stratification . Fire, or similar heat treatment, is necessary to crack the seed coat to allow for absorption of water and subsequent germination. Maximum germination occurs with the sequence of fire and a natural stratification period of 10 to 16 weeks [10,17,38,55,80,82]. Whitethorn ceanothus was observed to be germinating profusely on logged areas, perhaps because of heat from insolation .
Fire aids in the germination of seeds but can also destroy them. High intensity or high frequency fires can be detrimental to the seed bank and can result in lower rates of germination [22,68,80,82]. Overall, fire appears to be beneficial in promoting seed numbers, germination, and seedling population [52,68].
The initiation of germination depends on the following: how long the seeds had been dormant; length of time since the last soil disturbance; heat of previous fires; amount of moisture in the soil; persistence of the winter snow pack; soil temperatures; sun exposure; and how deeply the seed was buried .
Seedling establishment/growth: Gratkowski  notes that whitethorn ceanothus seedling establishment is much higher in burned areas than in nonburned areas, where it is almost nonexistent. Biswell  states that seedlings are seldom seen except where there has been fire. Nevertheless, the mortality of Ceanothus spp. seedlings is high during the first 2 postfire years . Environmental factors that affect the growth and survival of these seedlings include insects and other animal browsing, damping-off fungus, soil moisture, exposure, and soil temperature. The first 2 weeks after emergence are the most critical for survival .
Asexual regeneration: Layering is common in whitethorn ceanothus at higher elevations where the weight of snow forces branches and stems down to the ground . Stump-sprouting from a lignotuber is also common after the top of the shrub is damaged [40,50].
Growth Form (according to Raunkiær Life-form classification)
Life History and Behavior
Seasonal development of whitethorn ceanothus begins with emergence and extends through a growing season ranging from 75 to 95 days depending on emergence date and elevation at which it is found. Germination of seedlings begins in late May and June, and they are usually well established by 4 weeks of age. The seedlings were observed to grow at a rate of 0.2 inches (0.5 cm) per week until late August when they began to go dormant. After the 1st growing season whitethorn ceanothus grow very rapidly. In mature whitethorn ceanothus new growth and flower bud swelling occur at the same time, ranging from late May to mid-June depending on elevation. Blossoming is expected about 10 days later and continues for approximately 23 days .
Molecular Biology and Genetics
Barcode data: Ceanothus cordulatus
Statistics of barcoding coverage: Ceanothus cordulatus
Public Records: 2
Specimens with Barcodes: 2
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: NNR - Unranked
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status (e.g. threatened or endangered species, state noxious status, and wetland indicator values).
Pests and potential problems
Fairly free from diseases, but is susceptible to crown and root problems related to agricultural soils and wet and poorly drained soils.
There a few main points to consider when managing whitethorn ceanothus. It increases with
disturbance and forms very dense, difficult to penetrate brushfields. It is regarded as a
very strong competitor that can hinder tree seedling growth and subsequent conifer regeneration
[22,57,94]. Whitethorn ceanothus may compete with tree seedlings, but it also provides ongoing
nitrogen that may improve the site for conifer establishment and growth after establishment.
Soil nitrogen, however, probably becomes most important for tree seedlings after they have
cleared the initial hurdle of establishment [49,76]. In the past, herbicide treatments and
allowing livestock grazing in whitethorn ceanothus brushfields were used as management options
to open the dense shrub canopy. This increased the amount of light reaching the young conifers in
the understory and decreased brush competition for soil moisture and nutrients. Initial applications
of herbicide resulted in 100% top kill and 20% whitethorn ceanothus mortality with plant mortality
reaching 90% after the 3rd application [35,39,40,43,92,103]. A study done by Hobbs and Radosevich
 concluded that the control of evergreen woody species such as whitethorn ceanothus in young
conifer plantations improved tree seedling growth and in some cases survival.
Conversely, whitethorn ceanothus is valuable as a browse species and if populations decrease,
the amount of available forage for wildlife and livestock is also decreased . Prescribed
burns are often used in land management to encourage the establishment of whitethorn ceanothus
because of its importance as a browse species . It is also beneficial as a nurse plant for
conifer and Sierra gooseberry seedlings, providing shade and available nitrogen .
Tappeiner  reported the average size of open-grown whitethorn ceanothus plants on ungrazed,
9-year-old tree plantations in the Sierra Nevada and Klamath Mountains. Average crown diameter
was 5.7 feet (1.7 m) and average height was 3.2 feet (.98 m). This information may be useful in
predicting shrub development.
Cultivars, improved and selected materials (and area of origin)
‘Maleza’ Cultivar: This was released by the Lockeford,Plant Materials Center, Lockeford, California in 1989. Maleza mountain whitethorn is well suited for medium to coarse textured, well-drained soils. It is adapted to the Tahoe Basin, but grows well at elevations down to 3500 feet where precipitation is adequate.
Contact your local Natural Resources Conservation Service (formerly Soil Conservation Service) office for more information. Look in the phone book under ”United States Government.” The Natural Resources Conservation Service will be listed under the subheading “Department of Agriculture.”
Mountain whitethorn seeds mature in late August and September. The seeds are contained within a triangular capsule. Collected capsules should be stored in paper bags and allowed to dry until they open and reveal the seeds.
The seed has a hard exterior coat and therefore a combination of soaking in hot water and cold storage pretreatments are necessary. Seeds should be placed in hot water, preheated to 180 degrees F., and then allowed to cool and soak for 24 hours. Following this hot water treatment, mix the seed with moist sand, place the mixture in plastic bags and store in the refrigerator.
Periodically check the bags for moisture and for swelling of the seed which indicates that they are close to germinating. Once the seeds have swollen, plant them in containers of potting soil and cover them with approximately ½ inch of soil.
After the plants have formed a third pair of leaves they can be transplanted individually to larger ½ to 1 gallon containers. The young plants will be ready for their permanent location in 1 ½ to 2 years. New plants should be watered occasionally until they are well established. Afterward, deep watering every 1 to 1 ½ months will be adequate to maintain uniform growth.
Container grown plants may be available from local nurseries. Dig a hole two to three times the diameter of the root ball and at least six inches deeper. Backfill the hole with six inches of native soil. Make a few, 1/8 inch deep vertical cuts in the root ball, or carefully “tease” roots away from the root ball with your hands to encourage roots to grow into the new soil. Set the plant into the hole and fill in around the roots, firming the soil with your hands as you fill, until the hole is half full. Fill the hole with water and allow it to settle. This will settle the silt and eliminate air pockets around the roots.
Backfill with enough planting mix so the plant will set at the same level it was growing at in the container. Water to allow soil to settle, then add more soil if necessary. Build a berm of soil to form a watering basin around the outer edge of the hole. Break the basin down after two or three years.
Relevance to Humans and Ecosystems
Importance to Livestock and Wildlife
Whitethorn ceanothus is an important browse producer for wildlife species . It is a major component of the diet of mule deer in the summer ranges of the Sierra Nevada and is also used by cattle on summer grazing allotments [9,17,27,49,57,58,85]. Gordon  suggests that the spine-tipped branchlets that develop after establishment may make the shrub less desirable to deer as a browse component. Whitethorn ceanothus is also browsed by bighorn sheep, goats, and domestic sheep [22,25]. Long-eared chipmunks collect and cache the seeds of whitethorn ceanothus [41,97]. High amounts of whitethorn ceanothus are eaten by pocket gophers in California . The fruit of the shrub is eaten by birds and small mammals . Whitethorn ceanothus also provides forage and nesting habitat for the dusky woodrat and part of the diet of the mountain pocket gopher . Whitethorn ceanothus is a host plant for the Great Basin tent caterpillar .
Palatability/nutritional value: Whitethorn ceanothus is an important browse species for deer because of its high crude protein content and palatability [9,22,25,49]. It does not, however, provide sufficient nutrients for optimum growth and development in mule deer and is more valuable when consumed along with other species . It is considered as a poor to fair browse species for livestock such as cattle, domestic sheep, and goats [22,25,73].
Cover value: No information is available on this topic.
Value for rehabilitation of disturbed sites
Whitethorn ceanothus has considerable value when used for site amelioration. It is used for erosion control on slopes, terraces, and steep banks [78,89,90]. Whitethorn ceanothus is very important for rehabilitation because of nitrogen-fixing and other soil-building attributes. It is tolerant of severe sites and can play a soil building role on these sites [22,49]. It has successfully been used for these purposes in the Lake Tahoe Basin and Lost Canyon, California [15,19,89,90].
A list of available/potential seed sources can be acquired in the USDA, NRCS Commercial Sources of Conservation Plant Material, available online .
Mountain whitethorn can be used for ground cover on slopes, terraces or steep banks and as a barrier plant. Mountain whitethorn may be allowed to assume natural forms or may be shaped through pruning and pinching off the growing tips.
Ceanothus cordulatus is a species of shrub in the buckthorn family Rhamnaceae known by the common names mountain whitethorn and whitethorn ceanothus. It is native to California and adjacent sections of Oregon, Nevada, and Baja California, where it grows on mountain ridges and other forested areas. This is a spreading shrub growing usually wider than tall and up to about 1.5 meters. The stems are gray, with the twigs yellow-green in color and fuzzy in texture when new. The evergreen leaves are alternately arranged and up to 3 centimeters long. Each is oval in shape with three ribs and generally not toothed. The leaves may be hairy or not. The inflorescence is panicle-shaped, up to about 4 centimeters long. The flowers are white to off-white with five sepals and five petals. The fruit is a rough, ridged capsule up to half a centimeter long. It has three valves inside, each containing a seed.
Names and Taxonomy
specific to whitethorn ceanothus is not available, references will be made to the genus Ceanothus.
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