Redstem Filaree (not native)

The San Elijo Ecological Reserve is home to four similar, non-native species in the genus Erodium, often called filaree. The species also bear several names involving bird beaks and alfilerilla, from the Spanish word for pin.  The most common Erodium species is redstem filaree (E. cicutarium). Redstem filaree is an aggressive spreader and often carpets newly disturbed areas before native species can regain their hold. In the Reserve, filaree rarely invades establish plant communities but is a pesky problem in areas being revegetated. As fast as the non-native plants are removed, the filaree moves in.

On the other hand, species of filaree are excellent forage for horses, cows and sheep – better than most of our native grasses and forbs which can not survive heavy grazing pressure from domestic livestock.  As described by Cronise in 1868 ⁴⁷⁴

              … To the eye alfilerilla is a flattened tuft, hugging the ground.  It appears to give scarcely a fair hold to the bite of cattle, but, if lifted up, it shows a great mouthful.

Description ^{2,4,11,23,59,340,552}  

Redstem filaree (Erodium cicutarium) is a low-growing annual or biennial from a deep taproot. Early leaves form a ground-hugging rosette of fern-like leaves.  Leaves are generally less than 3 inches (7.5 cm) long; pinnately divided into numerous leaflets that are themselves pinnately divided. Stems, midveins and leaf edges may be tinged with red. Plants are covered with glandular and non-glandular hairs.

Flowers occur in loose clusters of two to seven flowers from one or more upright, branched, leafy stems. Pale magenta flowers are held four to twenty-four inches (10 – 50 cm) above the basal rosette.  There are five sepals and five petals of about equal size. Each sepal is tipped with a finger-like projection. A petal is ovate to elliptic, tapering or clawed at the base; there are often three dark veins from the base. The five stamens have anthers that are dark reddish-purple when mature. The single pistil consists of a superior five-lobed ovary and five styles that are united into a single column with five red-purple “fingers” spreading at the top. In the Reserve, blooms may begin as early as November and continue through June.

A fruit has five seeds, each with a long terminal projection (an awn) derived from the style. Awns are loosely attached along the style column and together they are called the beak. A cluster of fruits often resembles a group of birds with upraised beaks – giving the plant its common avian names.

Classification ^11,59,143  

Erodium is a genus in the geranium family (Geraniaceae), which is characterized by having five free petals, 5 or 10 stamens and a superior ovary with five chambers and five styles united into a style column that ends with five filamentous lobes that spread out like fingers. In the fruit, the awns elongate into a needle-like beak. At maturity, the dry fruit splits apart to release the seeds.

In the Reserve four species of Erodium and two species of Geranium have been reported. Only G. caroliniatum is native, and it is uncommon.

Ecology

Most plants disperse their seeds with the help of birds and animals or wind or water. However, in a few plants, including several filarees, seeds are self-propelled and self-burying.

In the mature fruit of redstem filaree, the needle-like awn at the top of the seed is hygroscopically active, coiling when dry and relaxing when wet. Initially all five awns in a flower adhere to one another along the style column; this attachment holds the awns straight. As the fruit dries, the internal stresses of each awn cause it to try to coil, and the tension developed abruptly pulls the seed away from the fruit; there is enough force to propel the seed and the awn as much as 18 inches (50 cm) from the parent plant.  Short videos of this process are given in some references.^{41 550 552}

Even after becoming detached from the parent plant, the awn continues to coil and straighten as ambient moisture varies. This movement causes the seed to twist and cartwheel along the ground until the seed encounters a depression or crevice. This halts its motion, and the effect of the changing shape of the awn is to cause the seed to burrow further into the ground until it is buried.⁵⁵¹

The initial dispersal moves the seed far enough from the parent plant to lessen competition, while retaining the seed in the habitat in which the parent plant was successful. The subsequent movement puts the seed below ground where it is protected from predation and environmental fluctuations, and where it may get an early start at germination.

Human Uses

The introduction of filaree into the Americas was closely associated with the introduction of domestic livestock.⁵⁴⁹ Filaree has coexisted and co-evolved with domesticated cattle, horses and sheep for at least 10,000 years and, unlike our native forage species, it is adapted to the heavy grazing pressure provided by managed herds. Much of the success of filaree in California may be due to the abundance of non-native livestock and the greater ability of filaree to withstand heavy grazing.

A major use of filaree has always been as a forage crop. Filaree is mentioned in the accounts of early explorers, such as Capt. Frémont, a botanist and naturalist who produced the earliest baseline of California’s herbaceous flora: “The face of the country was beautiful with a luxuriant growth of geranium (erodium cicutarium), so esteemed as food for cattle and horses”⁴⁷⁴

In 1896, in what may have been California’s first popular wildflower book, Parsons wrote: “This plant [redstem filaree] is found in abundance everywhere, and is one of our most valuable forage plants.”³⁹⁹  (She also adds “Children call them clocks, and love to stand the seed up in their clothing and watch the beaks wind slowly about, like the hands of a timepiece.”)

And a recent U. S. Department of Agriculture report concludes  “Redstem stork’s bill is important forage for cattle, horses and domestic sheep in California, Nevada and Arizona.” . . .  “The plant is resilient under heavy grazing pressure.”⁵

Interesting Facts

At the top of the redstem filaree seed, just below the awn are two tiny structures, called pits, which may be subtended by one or two furrows. A few references ^2,4,59 use pits to characterize Erodium species, but most do not mention them, perhaps because they are too small for the usual field identification.

The pits are quite intricate structures.⁵⁹ They are not random growths as from an injury or infection. Were they bigger, they might be vacuum cleaners, or cache pots or defensive devices from a Harry Potter adventure.

What are they? Do/did they have a function? Are they associated with the seed-driving motions of the awns?  Are they remnants of some past feature no longer functional? If anyone has an answer, please let us know.