CALIFORNIA NATIVE PLANT SOCIETY
Channel Islands Chapter
Rare Plant Profiles: Arceuthobium divaricatum
Arceuthobium divaricatum Engelmann, Pinyon Dwarf Mistletoe, is a perennial stem parasite plant in the Viscaceae (Mistletoe Family) using Pinus monophylla, P. edulis, and P. quadrifolia, the pinyon pines, as its host.   Its stems and leaves are olive-green to brown, 7-12 cm long and 2-4 mm wide at the base.   Arceuthobium divaricatum is found closely associated with its host plant, found in Singleleaf Pinyon Pine Series/Pinus monophylla Alliance vegetation from 1,400 to 2,300 m elevation.   Its seeds are translucent, round, and sticky, and mature in September and October.

Arceuthobium divaricatum photo by David Magney Arceuthobium divaricatum close-up photo by David Magney


Arceuthobium divaricatum ranges from southern California to western Texas, including Nevada, Utah, and Colorado, and northern Mexico.   This range is generally the same distribution of its host plants, Pinus monophylla, P. edulis, and P. quadrifolia, pinyon pines.   In California, it is known from Fresno, Inyo, Kern, Los Angeles, Mono, San Bernardino, and Ventura Counties.   A total of 67 voucher specimens have been deposited in one or more public California herbaria, representing a total of approximately 52 distinct populations:
  • 2 in eastern Fresno County (Sierra Nevada);
  • 12 in Inyo County;
  • 3 in eastern Kern County;
  • 6 in northern Los Angeles County;
  • 1 in Mono County (White Mountains in Jeffrey Mine Canyon at 7,600 ft);
  • 27 in San Bernardino County; and
  • 2 in northern Ventura County, and 7 other known (unvouchered) northern Ventura County occurrences.
There are approximately eight extant populations/occurrences in Ventura County, including the small population present east of the Ridgelite Mine in the northeastern corner of Lockwood Valley, with most occurring in the Cuyama Badlands area of northwestern Ventura County.   There is at least one population on Mount Piños in the Seymour Creek drainage.


Rarity Status
Global rarity ranking: G5.
State rarity ranking: not ranked.
CNPS State Inventory: Not listed.
CNPS Ventura County Uncommon, between 6 and 10 populations countywide (Magney 2008).


Impacts/Threats to Species
Arceuthobium divaricatum is threatened with extirpation locally from timber harvesting (for firewood), mining (such as for mine expansion at Pacific Custom Materials/TXI’s Ridgelite Mine in northeastern Ventura County, and mistletoe eradication efforts by the U.S.D.A. Forest Service, who considers all mistletoe species to be serious pests.   The BLM has cleared hundreds of acres of Pinyon-Juniper Woodland habitat in eastern Nevada, eliminating habitat (e.g. northeastern flank of Wilson Creek Range in Lincoln County), and possibly populations of, Arceuthobium divaricatum.

photo of cleared PJW in eastern Nevada by David Magney


Recommendations
Due to the scarcity of populations of Arceuthobium divaricatum in California, and because of anthropogenic threats to it, the following recommendations are made:
CNDDB State rarity ranking: S2.2
CNPS List: 2.2 or 4.2
CHANNEL ISLANDS CHAPTER, CALIFORNIA NATIVE PLANT SOCIETY, PO Box 6, Ojai, CA 93024-0006
Special thanks to Carlin Moyer for the beautiful illustrations on our site.   Photographs and maps are by David Magney.
Created: 11 September 2008; Last updated: 11 September 2008
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