Today's entry is written by my UBC Botanical Garden colleague Eric La Fountaine, and also includes two of his photographs (the first two). I've added the third photograph to illustrate the inflated stems that Eric writes about, though I've long intended to get better images of this species -- maybe this spring. Eric writes:
At first, I thought this plant was a dead "skeleton" left from the last season's growth. As I approached, I was surprised to find flowers--it was late December in Anza-Borrego Desert State Park. I had no idea what plant I was looking at. Daniel later identified it from the photographs. Eriogonum are often tricky to identify; there are around 250 species and many of them are found in California (Eriogonum in the USA and Canada). Species found in Anza-Borrego Desert State Park have been inventoried, which helped narrow the range of possibilities.
Eriogonum inflatum often has inflated stems, as shown in Daniel's photograph. Initially, botanists described plants with or without inflated stems as var. inflatum and var. deflatum. A.M. Stone and C.T. Mason, Jr. (Desert Plants Vol. 1, 1979) proposed that the swollen chambers were the result of larval feeding insects and the plants were not a separate variety from non-inflated ones. Later research revealed that while the chambers are used as larders or for winter protection by insects, the inflations were also commonly found on plants without insects present (Peter W. Price, The Southwestern Naturalist, 1982). If not caused by insects, why did the plants develop these swollen stems? It was noted that the inflations are less common in drier conditions. Dr. James L. Reveal of the University of Maryland, an authority on Eriogonum (he wrote the Flora of North America treatment: Eriogonum) has addressed the riddle: the swollen chambers have a high concentration of carbon dioxide and seem to be involved in gas regulation. Possibly, the inflations give photosynthetic advantages--making more CO2 available and providing additional stem surface area to a plant that supports few leaves in the dry desert environment.
Flora of North America has an excellent description and notes on Eriogonum inflatum. Commonly known as desert trumpet, it is found at lower elevations in the southwestern USA and in Baja California and Sonora, Mexico. It's not too surprising that I found flowers on the plant, as it can flower year round. The plant in my photographs reached a good height, perhaps 50-60 cm tall, but the species can grow larger, to as much as 1.5m. Southwestern North American indigenous peoples sometimes used Eriogonum inflatum as a food source and the inflated stems were used as drinking straws or fashioned into smoking pipes, hence another common name, pipeweed.