The Dodder's of Eaton Canyon

The Cuscutas (Dodder) of Eaton Canyon and the San Gabriel Mountains
By Susan Hopkins aka squirrelbait

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.

There are two common species of dodder in the San Gabriel Mountains, Cuscuta californica and Cuscuta subinclusa. While at first glance they appear very similar, there is a way to tell them apart. By their host plants and their flowers.

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
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
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.

Cuscuta californica, California Dodder
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

Cuscuta subinclusa, Canyon Dodder

Flowers: The corolla tube is very long and narrow with no or nearly so filaments.

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

Publicado por squirrelbait squirrelbait, 14 de septiembre de 2021

Comentarios

Thanks for this post! I'll try to be more observant of the host plants in the future and may go back through some of my older dodder observations to see if I can ID to species.

Publicado por amyjaecker-jones hace alrededor de 1 mes (Marca)

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