Cuscuta jepsonii

Kartesz (1999) and some other treatments (e.g. Hickman 1993) include C. jepsonii in C. indecora var. indecora. In contrast, Costea et al. (2006) recognize C. jepsonii as a distinct species because its infrastaminal scales are completely reduced, stating "Infrastaminal scales vary to some extent in many Cuscuta species. Nevertheless, we know of no instance of complete reduction of infrastaminal scales in a species where scale development is characteristically normal, even if variable. For this reason, and until additional material can be studied, C. jepsonii is maintained as a distinct species." C. jepsonii was known only from the type specimen, collected in 1892, however new collections were discovered during a herbarium survey and phylogenic analyses on the new collections support the conclusion that C. jepsonii is distinct (Costea and Stefanovic 2009). C. jepsonii is accepted by Baldwin et al. (2012) and by Costea and Nesom in FNA (2023, vol. 14).

Cuscuta jepsonii is a parasitic plant that occurs in the western United States, where it is known only from California in the Klamath and High North Coast Ranges and Mount Shasta in the High Cascades, south to the Southern Sierra Nevada. It has been documented at 21 sites since 2009 and is known from several additional older collections. The species was originally described in 1921, but was lumped into Cuscuta indecora var. indecora by many subsequent treatments. It was later recognized as a distinct species based on the complete reduction of its infrastaminal scales. The primary threat to this species is logging, or other land management actions, that remove its host tree species. The density of host trees impacts the success of seedlings, which have a short window to make connection with the host tree. Cuscuta jepsonii has two known host species, Ceanothus diversifolius and Ceanothus prostratus.

Cuscuta jepsonii occurs in the western United States in California, with collections spanning from the Klamath and High North Coast Ranges and Mount Shasta in the High Cascades, south to the Southern Sierra Nevada (Costea and Stefanovic 2009, CNDDB 2021).

There are 28 occurrences documented, 21 of which were observed in the last 20 year (CNDDB 2021).

Cuscuta have a short window of 7-21 days after germination for the seedling to make contact with the host plant, thus limitations in host availability would negatively impact this species. The main threat to this species is logging/tree removal which could inadvertently remove the species host tree (CNDDB 2021).