The Santa Cruz tarplant is listed as threatened under the federal Endangered Species Act (ESA), and endangered under the state of California Endangered Species Act (CESA).
Holocarpha macradenia, commonly known as the Santa Cruz tarplant, is an endangered plant endemic to Northern California.[2] Alternative common names for this plant are Santa Cruz tarweed or Santa Cruz sunflower.
Specifically Santa Cruz tarplant likes to inhabit terraced locations of coastal or valley prairiegrasslands with underlying sandy clay soils. Its characteristic habitat is in the California coastal prairie ecosystem, which may be the oldest stable ecosystem of the temperate world dating from about 600,000 years ago.
Description
Santa Cruz tarplant is an annual wildflower that can grow to 50cm tall, but is often much smaller. The flowering period is June to November. The growth habit is a single erect stem with larger specimens developing branches. Its leaves are linear and manifest longer near the plant base. The lower ranging leaves exhibit sharp, short teeth at their edges, while the upper leaves present edges that are rolled back, leading to a bristly feeling. Several other species have a similar general appearance, and can be easily mistaken for the Santa Cruz tarplant. The real Santa Cruz tarplant, though, has distinctive glands (see photos) that are not present in lookalikes.
Holocarpha macradenia, commonly known as Santa Cruz tarweed, illustrating distinctive glandsZoom view of distinctive glands, one circled in red.
The aroma of the plant has variously been described as strong, citrusy, tangerine and Christmas tree-like. The pungent smell protects it by repelling many would-be feeders.
It has characteristic yellow daisy-like flowers, with black anthers giving the appearance of striking black dots in the flower center. It is distinguished by its large number of flowers: 8 to 16 three-lobed outer ray flowers and 40 to 90 central disk flowers, more than any others in the genus Holocarpha. The flowers are situated in dense clusters at the branch tips or along the branch on a very short stem.
Drought tolerance
The Santa Cruz tarplant has an extremely long tap root, allowing it to thrive longer into the season than most coastal wildflowers. The plant produces seedbanks, which may not germinate in the next season, but which can remain viable over a period of years. Blooming season is summer, when there is less competition for pollinators and also less competition for sunlight, since in its range many plants have died back from the summer drought. Further protection from the rainless summer is a resinous coating on leaves and stems, allowing retention of water until late in the season. These resins often adhere to livestock, and, in the case of facial adherence, lead to a mascara-like effect after dust adheres to the resin in turn.
Protection and current status
Santa Cruz tarplant had been considered almost extinct by the year 1960. Subsequently, it was listed as a California endangered species and federal threatened species.[4][2] Colonies are found in the city of Santa Cruz at the Arana Gulch greenbelt and near De La Veaga Golf Course, Twin Lakes, and along Graham Hill Road;[5] in the city of Watsonville in grasslands along Harkins Slough plus a 3.4 acre coastal prairie called Tarplant Hill next to Struve Slough,[6] Spring Hills Golf Course, and on Watsonville Airport property;[7] and in the Elkhorn Slough watershed at the Elkhorn Slough Foundation's Porter Ranch in Monterey County.[8]
In the 1980s other colonies were found in the San Francisco Bay Area, including a colony in Pinole, western Contra Costa County. Ex-situ conservation of that colony was used to allow construction of a new shopping center, and a limited number of seeds from that population were moved immediately across and east of Interstate 80 onto the CalTrans right-of-way.[9] Additional seeds from that population were moved onto East Bay Regional Parks property, where most of these introduced populations died.
In another touch-and-go experiment, Santa Cruz tarplant has been shown to barely survive at the Arana Gulch colony in Santa Cruz, mostly due to lack of appropriate management, habitat fragmentation, and competition with non-native species. Active restoration experiments began in 2007 at Tarplant Hill in Watsonville by the owners, with support from the U.S. Fish and Wildlife Service Partners in Restoration Program.
Populations protected as critical habitat
In 2002, the US Fish and Wildlife Service published the final designation of Critical Habitat for the species, as follows: UNIT A - Mezue (Contra Costa County, Wildcat Canyon Regional Park) - County/City ownership. UNIT B - Graham Hill - Private ownership. UNIT C - De Laveaga - State ownership. UNIT D - Arana Gulch - County/City ownership. UNIT E - Twin Lakes - State ownership. UNIT F - Rodeo Gulch - Private ownership. UNIT G - Soquel - Private and County/City ownership. UNIT H - Porter Gulch - Private ownership. UNIT I - Watsonville - State, County/City and Private ownership. UNIT J - Casserly - Private ownership. UNIT K - Elkhorn - Private ownership.
In 2002, a total of 1,175 ha (2,902 acres) was designated as Critical Habitat.[10]
Efforts at active management to restore plant populations
The Arana Gulch populations management, the City of Santa Cruz established their Adaptive Management Working Group (AMWG) which consisted of a group of stakeholders, whose composition was approved by the California Coastal Commission Executive Director. The members have been a researcher from UC Berkeley, a biologist from California Fish and Wildlife, a biologist from US Fish and Wildlife Service, an ecologist from the California Coastal Commission, three private consultants, a UC Cooperative Extension Livestock advisor, and Santa Cruz city staff from the Planning and Parks Departments. Semi-annual meetings were held from 2013 to 2016, with the last meeting March 14, 2016.[11]
Twin Lakes State Park (Unit D0 population management between 1998 and 2003 consisted of mowing in 1998, 1999, and 2001 once in spring, and once in fall using a string trimmer. The litter was then removed using garden rakes or McCleods. The site was scraped using McCleods. In 2002, mowing continued and 15 nursery raised plants planted on February 6. The nursery plants were more robust and produced over ten times the number of seed heads than the naturally occurring individuals.
In 2002, 494 plants were grown from seeds harvested in previous years, and 344 of these plant survived, but were no more robust than the naturally occurring individuals. In 2002, where plants naturally occurred, was mowed twice as well as treated with a chain harrow.[12]
Population trends in individual plant populations
Ecological restoration projects to restore individual populations of the plants, their annual reports usually contain plant counts or estimations of the numbers of plants with a population during a certain year, and that data can be used to measure trends and successes of the restoration techniques used.
The Arana Gulch (Unit D) population first census in 1986 by Randy Morgan estimated that there were 100,000 plants on that site in Santa Cruz in four different "Areas", and by 2006 was extinct in three of the four areas, and in the remaining "Area A" had dropped to only 348 plants. Plants counts in 2013 only found 18 plants, in 2014 only 4 plants, and in 2015 zero, and 2016 34 plants. Zero plants at Arana Gulch grew in 2017, then 267 in 2018, and 47 in 2019.[13]
The 2020 census at Arana Gulch found only a single wild plant growing in Area A, even though there were several growing earlier in spring that the cattle ate, plus five planted seedlings had survived over in Area C. The amount of native and weed cover of each "Area" was surveyed in October 2020, as follows: AREA A = 72% weed grasses, 4% broadleaf weeds, 3% native grasses—Danthonia, and 4% wildflowers—poppies, and the remainder bare dirt. AREA B (never grazed) = 44% weed grasses, 41% native grasses—Bromus, 3% broadleaf weeds and the remainder bare dirt. AREA C = 72% weed grasses, 3% native grasses—Bromus, and 25% bare soil. AREA D (not grazed in 2020) = 97% weed grasses and 3% native grasses—Bromus.[14]
As a comparison to the decades of work being done at Arana Gulch, only five miles south at 300 Byers Lane in La Selva Beach on 70 acres of private property—the same area and habitat as the Arana Gulch property—the native grassland habitat at Byers Lane, started as 99% weed-covered, and was restored back to 95% native cover in only ten years.[15]
The Arana Gulch restoration methods tried so far, are burning, grazing annually with cattle, and scraping. Three of the four former plant population "Areas" are surrounded by permanent barbed wire cattle fencing[16]
The "Tarplant Hill" population in Watsonville (part of the Unit I populations) has experienced an almost identical drop in the plant numbers in that population. The plant count in 1984, estimated 10,000 plants, 1985 100,000 plants, 1986 20,000 plants, 1989 400,000 plants, and in 1990, 38,000 plants were estimated. Then in 1993, 1994, and 2003 only a single plant was found for that whole "Tarplant Hill" population. Then, counts in 2004, found 8 plants, 2005 60 plants, 2008 two plants, 2007 70 plants, 2008 59 plants, and the 2009 count found 189 plants.
The Twin Lakes population, which is part of Unit D is on State Park property, and the naturally-occurring plant numbers were 16 in 1999, 7 in 2000, 19 in 2001, 7 in 2002 and only 5 plants in 2003.[17]
A 2020 review of the East Bay populations, outlined the history and current status of the tarplants in that area. In the 1980s, the land where the wild population was growing, was the site of a future shopping mall. A project spearheaded by Neil Havlik, collected seeds and planted them for two years, into more than 30 sites, at Sobrante Ridge Regional Preserve, Tilden and Wildcat Regional Parks, and also, properties owned by East Bay Municipal Utility District. These populations only continue to grow currently in three locations, all of which are within Wildcat Canyon, and the largest stand is along the Mezue trail.[19]
Arana Gulch population studies
The entire Arana Gulch wild population dropped to a single plant in October 2020, in "Area A", the last of the four original "areas" where 100,000 plants were originally found growing 35 years earlier.
January, 2021, the City of Santa Cruz Parks & Recreation Department's Open Space & Greenways team, in collaboration with the Arana Gulch Adaptive Management Working Group, the UCSC Greenhouse, and UCSC volunteers, did an experimental outplanting of 400 Santa Cruz tar plant, to try and ensure its persistence as a key goal of the Arana Gulch management plan. An additional 400 tarplants were scheduled to be planted in February. The short-term goal of this experimental outplanting is to identify the best outplanting methods. The long-term goal is to increase the seedbank of the tarplant at Arana to a level that will ensure a high probability of persistence for 100 years, or in perpetuity. This planting is something of a landmark—if successful could potentially exceed the targeted population goal for the Santa Cruz tarplant management program.[20]
Also in 2021, four studies were conducted of the Arana Gulch Critical Habitat Unit, where in the 1990s tarplants were divided into four population clusters--"Areas" A, B, C and D. Areas A, C and D have been grazed for several years, with the hopes that would increase the tarplant population. Instead, the tarplant population dropped to zero in two of the last six years, and only one single plant survived in 2020.
These studies were conducted, to determine the health of the Coastal Prairie habitat which the tarplant is a member, and what improvements could be made to produce future self-sustaining populations.
Study 1: How many exotic seeds are in the soil, that could potentially interfere with tarplant seedling survival? One square foot boxes were filled with topsoil, three inches deep from the four "Areas" in November 2021, and sown with California poppy seeds as a native plant stand-in for tarplant seeds, and watered daily. As seedlings germinated, they were identified and counted. Weed seedling counts indicate that tarplants have a massive amount of weed competition, with 129-516 weed grass seedlings sprouting in each box, that overwhelmed and killed all of the poppy seedlings that sprouted.
Three different soil samples were taken from Area A, plus one sample from each of Areas B, C and D. The number of weed grass seedlings that sprouted per square foot were: Area A = 129–374. Area B = 451. Area C = 464. Area D = 516. The broadleaf weed seedlings were also an important issue: Area A = 8–17. Area B = 29. Area C = 45. Area D = 33 per square foot.[21]
Study 2: Has cattle grazing over time, remove soil nutrients that tarplant seedlings need for survival? Wood boxes, one square foot each, were filled with topsoil and poppy seeds sown as a stand-in for the tarplants, and all other seedlings as they sprouted removed, leaving the poppy seedlings to grow unmolested. However, the poppy seedlings soon showed they were nutrient-starved by their lack of growth and leaf-color. Organic fertilizers and organic matter were added periodically, until the plants started to thrive.[22]
Study 3: Is there a connection between where wild tarplants grew in the past, with the percentage of Coastal Prairie cover in Area-A? Locations in Area A where wild tarplants grew over the past 25 years had been previously mapped. Sixteen linear vegetation-cover transects were run for 200 feet in slices 25 feet apart across those wild tarplant locations, and 20 x 25 foot polygons were produced from two-foot apart sampling points. Overlaying the location of wild tarplant on top of the vegetation cover survey, found that the tarplants at Arana Gulch seem to need a high quality Coastal Prairie matrix to maintain a self-sustaining population, that is approximately 80-95% native grass cover, consisting of a 60% Danthonia-30% Stipa-10% native Bromus species mix.[23]
Study 4: Tarplant seedlings planted out, what genetic diversity exists in the Arana Gulch population? Spring 2021, UCSC-greenhouse grown seedlings, sprouted from originally wild-harvested Arana Gulch seeds, were planted out in Area-A. Photographed in June, 2021, showed that there were at least twelve different forms of the tarplant seedlings—from plants with widespread branches, to round compact shapes, and each flowering at slightly different times and in different manners. Since all of the seedlings were grown from seeds originally collected from wild plants at Arana Gulch, this planting acted as a perfect "common garden" study, to detect genetic variations within the population.[24]
The Mooloolah River National Park is a nationally protected area located on the Sunshine Coast, Queensland. It covers an area of 830.9 hectares and is bordered by the Mooloolah River to the east, Claymore and Dixon Roads to the west, and the Lower Mooloolah River Environmental Reserve to the south. It is bisected by the Sunshine Motorway with the northern, 161.93 hectare component of the Park being a later addition. The Park was initially vacant crown land prior to national park designation in 1960. Surrounding land uses include livestock grazing, urban development and the campus of the University of the Sunshine Coast. It is the second largest mainland park on the coastal lowlands in South East Queensland after Noosa National Park and represents an example of low-lying coastal floodplain distinctive of the region.
Watsonville is a city in Santa Cruz County, California, in the Monterey Bay Area of the Central Coast of California. The population was 52,590 at the 2020 census. Predominantly Latino and Democratic, Watsonville is a self-designated sanctuary city.
Bromus tectorum, known as downy brome, drooping brome or cheatgrass, is a winter annual grass native to Europe, southwestern Asia, and northern Africa, but has become invasive in many other areas. It now is present in most of Europe, southern Russia, Japan, South Africa, Australia, New Zealand, Iceland, Greenland, North America and western Central Asia. In the eastern US B. tectorum is common along roadsides and as a crop weed, but usually does not dominate an ecosystem. It has become a dominant species in the Intermountain West and parts of Canada, and displays especially invasive behavior in the sagebrush steppe ecosystems where it has been listed as noxious weed. B. tectorum often enters the site in an area that has been disturbed, and then quickly expands into the surrounding area through its rapid growth and prolific seed production.
Cortaderia selloana is a species of flowering plant in the Poaceae family. It is referred to by the common name pampas grass, and is native to southern South America, including the Pampas region after which it is named. It is widely distributed throughout the world as a cultivated ornamental and an invasive species.
Genista monspessulana, commonly known as French broom, Montpellier broom, or Cape broom (Australia), is a woody leguminous perennial shrub. The yellow-flowering bush is native to the Mediterranean region, and while it may still be commonly sold in some garden stores, it is considered an invasive plant in most places where it has been introduced. It is a noxious weed on the western coast of the US and in parts of Australia.
California coastal prairie, also known as northern coastal grassland, is a grassland plant community of California and Oregon in the temperate grasslands, savannas, and shrublands biome. This ecosystem is found along the Pacific Coast, from as far south as Los Angeles in Southern California to southern Oregon. It typically stretches as far inland as 100 km, and occurs at altitudes of 350 m or lower.
Melilotus albus, known as honey clover, white melilot (UK), Bokhara clover (Australia), white sweetclover (US), and sweet clover, is a nitrogen-fixing legume in the family Fabaceae. Melilotus albus is considered a valuable honey plant and source of nectar and is often grown for forage. Its characteristic sweet odor, intensified by drying, is derived from coumarin.
The Santa Cruz cypress is a species of North American tree within the cypress family. The species is endemic to the Santa Cruz Mountains within the Santa Cruz and San Mateo counties of west-central California. The U.S. Fish and Wildlife Service listed the species on the Endangered Species Act in 1987 due to increasing threats from habitat loss and disruption of natural forest fire regimes. In 2016, the conservation status of the Santa Cruz cypress changed to Threatened. The cited reasoning was a decrease in threats against their habitat.
The California Floristic Province (CFP) is a floristic province with a Mediterranean-type climate located on the Pacific Coast of North America with a distinctive flora similar to other regions with a winter rainfall and summer drought climate like the Mediterranean Basin. This biodiversity hotspot is known for being the home of the Sierran giant sequoia tree and its close relative the coast redwood. In 1996, the Province was designated as a biodiversity hotspot allowing it to join ranks among 33 other areas in the world with many endemic species. To be named a biodiversity hotspot, an area has to contain species and plant life that cannot be found anywhere else in the world. The California Floristic Province is home to over 3,000 species of vascular plants, 60% of which are endemic to the province.
Potentilla hickmanii is an endangered perennial herb of the rose family. This rare plant species is found in a narrowly restricted range in two locations in coastal northern California, in Monterey County, and in very small colonies in San Mateo County. This small wildflower, endemic to western slopes of the outer coastal range along the Pacific Ocean coast, produces bright yellow blossoms through spring and summer.
The U.S. Fish and Wildlife Service (USFWS) has a number of programs aimed at Mission blue butterfly habitat conservation, which include lands traditionally inhabited by the Mission blue butterfly, an endangered species. A recovery plan, drawn up by the U.S. Fish and Wildlife Service in 1984, outlined the need to protect Mission blue habitat and to repair habitat damaged by urbanization, off highway vehicle traffic, and invasion by exotic, non-native plants. An example of the type of work being done by governmental and citizen agencies can be found at the Marin Headlands in the Golden Gate National Recreation Area. In addition, regular wildfires have opened new habitat conservation opportunities as well as damaging existing ones.
Arana Gulch is a creek and landform that forms part of the southeastern boundary of the city of Santa Cruz, California. The creek begins in the Santa Cruz Mountains and flows southwest into Monterey Bay via what was once called Woods Lagoon, now the Santa Cruz Small Craft Harbor.
San Gregorio Creek is a river in San Mateo County, California. Its tributaries originate on the western ridges of the Santa Cruz Mountains whence it courses southwest through steep forested canyons. The San Gregorio Creek mainstem begins at the confluence of Alpine and La Honda Creeks, whence it flows 12 miles (19 km) through rolling grasslands and pasturelands until it meets the Pacific Ocean at San Gregorio State Beach. It traverses the small unincorporated communities of La Honda, San Gregorio, Redwood Terrace and Sky Londa.
Arctostaphylos densiflora, known by the common name Vine Hill manzanita, is a very rare species of manzanita. It is endemic to Sonoma County, California, where it is known from only one extant population of 20 to 30 individual plants. These last wild members of the species are on land near Sebastopol which is owned and protected by the California Native Plant Society. In addition, there are five to ten plants of this manzanita taxon growing on private property about a mile away. The local habitat is mostly chaparral on sandy shale soils.
Taeniatherum is a genus of Eurasian and North African plants in the grass family.
The Ellicott Slough National Wildlife Refuge is a United States National Wildlife Refuge located in the northern part of the Monterey Bay area of California.
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Bocconia frutescens is a species of flowering plant in the poppy family known by many common names, including plume poppy, tree poppy, tree celandine, parrotweed, sea oxeye daisy, and John Crow bush in English, gordolobo, llorasangre, tabaquillo, palo amarillo, palo de toro and pan cimarrón in Spanish, bois codine in French and bwa kodenn in Haitian Kreyòl. It is native to the Americas, including Mexico, parts of Central and South America, and the West Indies. It is perhaps better known in Hawaii, where it is an introduced species and an aggressive invasive weed with rapid negative effects on local ecosystems. In other parts of the United States it is used as an ornamental plant for its "tropical"-looking foliage.
Younger Lagoon Reserve is a 72-acre (28-hectare) University of California Natural Reserve System reserve on the northern shore of Monterey Bay in Santa Cruz County, California. The site is owned by the University of California and managed for teaching and research. It is adjacent to Long Marine Laboratory.
An escaped plant is a cultivated plant that has escaped from agriculture, forestry or garden cultivation and has become naturalized in the wild. Usually not native to an area, escaped plants may become invasive. Therefore, escaped plants are the subject of research in invasion biology.
↑ Gary Deghi, C. Michael Hogan et al., Final Environmental Impact Report of the Pinole Valley Shopping Center for the city of Pinole, Earth Metrics Incorporated (1986)
↑ 50 CFR Part 17. Endangered and Threatened Wildlife and Plants; Final Designation of Critical Habitat for Holocarpha macradenia (Santa Cruz Tarplant); Final Rule. pages 63968-63992. Vol. 67, No. 200, October 16, 2002, Rules and Regulations
↑ Report - "Management Actions and Population Trends For the Twin Lakes Population of Holocarpha macradenia Santa Cruz Tarplant September 1998 thru July 2003" N/D by Tim Hyland, California State Parks Resource Ecologist Santa Cruz District
↑ Dremann, Craig Carlton. 2020. October 15 Vegetation Survey of the Arana Gulch Tarplant populations and Vegetation cover. Notebook #291, pages 12-16. Unpublished
↑ Dremann, Craig Carlton with Michael Shaw. 2002. Releasing the Native Swedbank: An Innovative Approach to Restoring a Coastal California Ecosystem. Ecological Restoration. Vol. 20, 2:103-107 - https://www.ecoseeds.com/shaw.pdf
↑ Arana Gulch Habitat Management Plan, City of Santa Cruz, Year 3 (2016) Annual Report.
↑ Report--"Management Actions and Population Trends For the Twin Lakes Population of Holocarpha macradenia Santa Cruz Tarplant September 1998 thru July 2003" N/D by Tim Hyland, California State Parks Resource Ecologist, Santa Cruz District.
↑ Restoration of Santa Cruz Tarplant (Holocarpha macrademia) and Coastal Prairie on Tarplant Hill, Santa Criz County. Cooperative Agreement #81440-7-J303. October, 2009. Annual report, reflects work accomplished during the time period September 1, 2007 - October 1, 2009
↑ Dremann, Craig Carlton. 2021. "Arana Gulch, Santa Cruz, California, the Four Tarplant Critical Habitat Areas-- Results of Box Tests of soil, counting weed seedlings sprouting from one square foot." https://www.ecoseeds.com/Arana-Gulch-Box-test-for-seedlings.pdf
↑ Dremann, Craig Carlton. 2021. "Arana Gulch Area-A native grass Coastal Prairie cover transects, west-east every 25 feet starting parallel to the southernmost fence, and the transect starting from the western fence line and going 200 feet eastward--compared with locations of the Endangered Santa Cruz Tarplant in one of its Critical Habitat Units" https://www.ecoseeds.com/Arana-Gulch-transects-AREA-A.pdf
↑ Dremann, Craig Carlton. 2021. "Endangered Santa Cruz Tarplant's (Holocarpha macradenia - Asteraceae) exceptional variations in genetic diversity, observed in nursery-grown seedlings spring 2021, planted in a "Common Garden" of the Arana Gulch, Santa Cruz, California - USFWS Critical Habitat Unit population." https://www.ecoseeds.com/Santa-Cruz-tarplant-genetic-diversity.pdf
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