It can be difficult to believe that these plants are part of the morning-glory family, Convolvulaceae. Cuscuta’s are a parasitic vine which climbs other plants and takes nutrition directly from them via haustoria, a root-like structure. Dodder resembles a pile of yellow-orange straw wrapped tightly around its host plant. It is mostly stem, the leaves are reduced to scales on the stem's surface, since they are not needed for photosynthesis while the dodder is obtaining nutrients from its host. It bears tiny white flowers which are only about 3 millimetres wide, and fruits which are even smaller. All dodders have a preferred host plant. Sometimes they will make do with what is available.
Photo : Cuscata california on Eriodictyon crassifolium. Note the haustoria.
Let’s start by looking at Cuscuta species that you are unlikely to find and get them out of the way. There are 3 rare Cuscuta that occur in the San Gabriel Mountains.
Cuscuta campestris on herbs and shrubs Elevation < 350m which has rounded calex, like a little ball.
Cuscuta denticulata Found in desert scrublands and Joshua tree woodlands. Tiny flowers shorter then wide, little teeth.
Cuscuta indecora on herbs, Maybe Lytle Creek Canyon, super rare with very pale threads.
Cuscuta pacifica There is a forth Cuscuta that tends to show up on the iNaturalist suggestion bar, Cuscuta pacifica or Pacific Goldenthread. C. pacifica is a halophyte, meaning that it is a salt-tolerant plant that grows in soil or waters of high salinity, living in coastal salt march habitats. Which means, you are not going to find this cuscuta in the San Gabriel Mountains or Eaton Canyon.
A hand lens is recommened for inspecting the flowers.
California Dodder
Cuscuta californica
Flowers: Shallow bell, with long filaments
Host plants: Parasitizes herb & shrubs; non-woody perennials and annuals
California Buckwheat * Eriogonum fasciculatum
White Sage Salvia apiana
Black Sage * Salvia mellifera
Yerba Santa* Eriodictyon crassifolium
Scale Broom/Broom Sage * Lepidospartum squamatum
Showy Penstemon * Penstemon spectabilis
Southern Monkey Flower * Diplacus longiflorus
Deerweed *
Phacelia (seen on an iNaturalist observation)
California Lilacs ** Ceanothus
* I have observed these relationships
** Cross-over host
Canyon Dodder
Cuscuta subinclusa
Flowers: The corolla tube is very long andEriodictyon crassifolium narrow with no or nearly so filaments.Eriodictyon crassifolium
Host Plants: Parasitizes woody shrubs and trees
Laurel Sumac * Malosma laurina
Poison Oak * Toxidendron diveralobum
Mule Fat * Baccharis salicifolia
Blue Elderberry Sambucus nigra
Bush Poppy Dendromecon rigida
Willow * Salix
Tree Tobacco * Nicotiana glauca
California Lilacs ** Ceanothus
* I have observed these relationships
** Cross-over host
I recently learned that Dodders can be hosts to a certain weevil, that creates a gall on the thin threads of the plant. So the Dodders have host plants and then they play host to weevil. I Love nature! https://www.inaturalist.org/taxa/231111-Smicronyx-sculpticollis
References:
Field Guide to the Flora of the San Gabriel Mountains, Orlando Mistretta, 2020
Wildflowers of Orange County and the Santa Ana Mountains, Robert L. Allen & Fred M. Roberts, Jr. 2013
Conversations with Robert Allen
Credits:
By Susan Hopkins