By Linda Jones.
The Broomrape family are parasites with specialized structures on the roots for taking food, water and nutrients from the host plants. There are over 200 species worldwide with about a dozen species in the San Diego area.
Some parasitic plants are well known, like Dodder (Cuscuta spp) which is a true parasite on other plants. It has no chlorophyll in its cells and so gets all its food, water and nutrients from the host plant. A successful parasite is one that does not kill its host, thereby keeping a supply of necessary food and hosts in the area. In the case of dodder, it dies after blooming, and the host can once again grow without the parasite robbing it of needed nutrients.
There are a number of flowering plants found in this area that are partial or hemi-parasites. These, like the familiar mistletoe (Phorodendron spp) that shows up at Christmas markets, are green due to the presence of chlorophyll in the cells. A hemiparasite can manufacture its own food but grows more vigorously and ensures sufficient energy for reproduction if it takes water and nutrients from its neighbors. Since only the hemiparasite’s roots attach to the host’s roots, it is hard to identify the host plant(s) and there is little in the literature that identifies specific hosts for different species of hemiparasites.
One of the plants that stirred my interest in parasitic plants was dark-tipped bird’s beak (Cordylanthus rigidus ssp setigerus) which I see growing annually along the Santa Carina trail in the San Elijo Lagoon. Dark-tipped bird’s beak is found in coastal sage scrub, chaparral and oak woodlands, in open and disturbed areas.
This is an annual plant, appearing about late winter and flowering from May to September. In the garden it is seasonal plant that reaches about 1-1.5m in height and has a pretty airy, open shape. Foliage is a colorful green and/or burgundy. It is unusual in that it reaches maturity during the hot, dry season, later in the year than most annuals. Its hemiparasite lifestyle may help it outlast other annuals.
The flowers are unusual and give the plant its common name, bird’s beak (see picture and use your imagination!). The whitish flowers are strongly bilateral with red-burgundy striping on the strap-like calyx and bract that bracket it. The flower produces heavy nectar but depends on heavier bee species like the bumblebees (Bombus spp), sweat bees (Halictus spp) and to a lesser extent hummingbirds for pollination since opening the two-lipped corolla to reach the nectar requires a heavier body.
Saltmarsh bird’s beak (Chloropyron maritimum ssp maritimum) once occurred in salt marshes from San Francisco to Baja but due to habitat loss (yet another example) it now only occurs south of Carpenteria. It is now listed as endangered both by the state and federally. Records for San Diego are from the southern marshes, Imperial Beach and Tijuana Slough.
Purple owl’s clover and the paintbrushes are closely related hemiparasites (Castilleja species) occurring in San Diego County.