dwarf-mistletoes

genus Arceuthobium

Member of mistletoes (tribe Visceae)
sandalwood family (family Santalaceae)
dicots (class Magnoliopsida)
flowering plants (subphylum Angiospermae)

There are no other wild species of this genus in the bay area.

Calflora and Jepson recognize only western dwarf-mistletoe (Arceuthobium campylopodum) in the bay area, but both treat gray pine dwarf-mistletoe (Arceuthobium occidentale) as a synonym. Meanwhile, iNaturalist and POWO treat these as two different species.

Although FNA treats gray pine dwarf-mistletoe (Arceuthobium occidentale) as a subspecies of western dwarf-mistletoe (Arceuthobium campylopodum), it at least gives me some clue how to tell them apart. Range is hard to resolve in sufficient detail from FNA, but iNaturalist includes only one non-occidentale subspecies which has been identified in the bay area, ssp. campylopodum. Therefore, the characteristics listed here are taken from FNA’s description of ssp. campylopodum and ssp. occidentale.

gray pine dwarf-mistletoe
Arceuthobium occidentale

plants usually forming localized infections only
principal host is gray pine (Pinus sabiniana)
by far the most common ID in the bay area, despite it being ignored by Calflora and Jepson

western dwarf-mistletoe
Arceuthobium campylopodum

plants usually forming witches’ brooms
third internodes 7–11 mm long, 1.5–2 mm thick
principal local host is ponderosa pine (Pinus ponderosa)

also on jeffrey pine (Pinus jeffreyi), but that isn’t found in the bay area

coastal dwarf-mistletoe
Arceuthobium littorum

plants usually forming witches’ brooms
third internodes 10–15 mm long, 2–3.5 mm thick
principal hosts are bishop pine (Pinus muricata) and monterey pine (Pinus radiata)
so far found just outside the bay area, but its hosts are here, so it’s probably just a matter of time before it is found locally

3 observed taxons / 1 key

Chris’s observations: 4 (1 is research grade)

Locations:

Henry Coe SP
Jacks Peak CP
Mt. Diablo SP
Pinnacles NP

Months:

Oct.: 2
Nov.: 1
Dec.: 0
Jan.: 0
Feb.: 0
Mar.: 0
Apr.: 1

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Taxon info: iNaturalist – Calflora – Jepson eFlora – FNA

Bay Area species: iNaturalist – Calflora