Arceuthobium campylopodum subsp. siskiyouense
Wiens & Nickrent) Nickrent, Phytoneuron 2012-51: 10. 2012.
Plants forming witches' brooms. Stems brown, 6–8(–10) cm; third internode 8–9(–15) × 2 mm, dominant shoot 2–2.5 mm diam. at base. Staminate flowers 3 mm diam.; petals 3 or 4. Fruits 4 × 2.5 mm.
Phenology: Flowering Aug–Sep; fruiting Sep–Oct.
Habitat: Coniferous forests, especially closed-cone pine forests with knobcone pine.
Elevation: 400–1200 m.
Meiosis likely occurs in July, with fruits maturing 13 months after pollination.
The principal host of subsp. siskiyouense is Pinus attenuata; rare hosts include P. contorta, P. jeffreyi, and P. ponderosa. Subspecies siskiyouense is endemic to the Klamath and Siskiyou mountains.