Rattlesnake Weed

Daucus pusillus

white flowers on top of stem
Rios trailhead | April 2011

Rattlesnake weed (Daucus pusillus) is a lacy little native plant with a flower that looks like a Victorian broach and a common name that suggests something less refined. It has some well known relatives, such as the tasty garden carrot and the deadly poison hemlock.

It is not known whether rattlesnake weed is an effective treatment for rattlesnake bites, but some native Americans and early Spanish apparently thought it was.

Other Common Names:

American wild carrot, southwestern carrot, Yerba de la Vibora, seed ticks

Description 4,11,26,59,67

In spite of its threatening name, rattlesnake weed is a delicate-looking annual plant. A short-lived clump of basal leaves arises from a small taproot and produces a single, often unbranched stem that grows to two feet (55 cm) or less. Stems are covered with short, stiff hairs. The foliage resembles that of the related garden carrot. Basal and cauline leaves are up to four inches (10.5 cm) long and are two to three times pinnately divided. Petioles are approximately the same length as the leaves, and their bases form U-shaped sheaths around the stem.

Flowers occur in compound umbels two inches (5 cm) or less in diameter, carried singly on top of a stem. Umbels are circular and flat or slightly depressed in the center. Each compound umbel is surrounded by a lacy collar of green, leaf-like bracts. Altogether, the neat cluster resembles a Victorian broach. (It has also been likened to a bird’s nest.4,67) Individual flowers are of the order of 1/32 inch (0.1 cm) across, too small for casual measurement. Most are bisexual, but a few staminate flowers may ocur in the center of an umbel. Sepals are absent. There are five white heart-shaped petals that are somewhat folded up along the midrib; There are five stamens and a single pistil with an inferior ovary that is barrel-shaped with radiating white bristles; there are two elongate styles with minute, capitate stigmas. Major bloom time is April to June.1

On maturity, the dry fruits split into two one-seeded halves, each half an ellipsoid with one flattened side, and less than 1/8 inch (0.25 cm) long. These often develop a pink tinge. They retain the pale bristles of the ovary and have new larger pink prickles that are barbed on the ends. Both types of bristles are superb snatching, grabbing devices for hitching a ride on fur, feathers or socks.

tiny white flowers bunched together at end of stem

Rios trailhead | May 2011

microscopic view of tiny white flowers

Close-up of flowering umbel showing prickly ovaries | Rios trailhead | May 2017

tiny red flowers on branch

Umbel with mature fruit | Santa Carina trailhead | May 2017

Distribution 7,89

Rattlesnake weed is native to California and is found across the southern United States and along the west coast from British Columbia to Baja California. In California, it is found is a variety of vegetation types below 5100 feet (1560 m) from yellow pine forests to grasslands to coastal sage scrub. It is considered a fire-follower, a plant that is more common after a fire.26,59

The is some discrepancy in descriptions of the habitat requirements of rattlesnake weed. This may reflect the regional variation. The NRCS67 reports it does not tolerate shade and can become “quite dominant” in pastures and grasslands. In southern California, it avoids direct sun, preferring small openings along the trails and between shrubs where it is partially or totally protected from direct sun.4,11 Under these circumstances, it rarely builds up large populations, although it can be dense in locally restricted areas.4

In the Reserve, rattlesnake weed occurs sporadically along the south side trails. In 2017, following drought-ending winter rains, it could be found in many areas, including the young restoration sites near the Santa Carina trailhead.

Classification 2,44,59,143

Rattlesnake weed is a dicot  angiosperm in the carrot family (or parsley family, Apiaceae). Members of this family are mostly herbs and are characterized by having flowers in compound umbels in which the peduncles of primary umbels also radiate from one point, forming a larger umbel. The term “umbel” comes from the Latin for sunshade, referring to an umbel’s resemblance to an umbrella. Previously, this family was called Umbelliferae. Members of this family often have a thick taproot, leaves that are pinnately divided or dissected, with petioles that wrap part way around the stem and a two-seeded dry fruit.

The carrot family includes important foods such as celery, carrots, and parsnips, and flavorful herbs such as parsley, cumin, coriander, dill, and caraway. The same family includes two extremely toxic plants: water hemlock (Cicuta maculata) and poison hemlock (Conium maculatum). The latter is a non-native plant that has become established in the Reserve.48 It is thought to be the plant that killed Socrates.56

Three other native members of the carrot family have been reported from the Reserve:48  shiny lomatium (or biscuit root, Lomatium lucidum), Pacific sanicle (or gamble weed, Sanicula crassicaulis) and California hedge-parsley (Yabea microcarpa).

Jepson eFlora Taxon Page
ariel view of leaves

Young plant | Santa Carina trailhead | May 2017

close up of tiny flowers bunched together

Santa Carina trailhead | April 2015

weed with small white flower pods on top

Santa Carina trailhead | April 2017

Ecology 41,337

Most seed-producing plants have developed one or more methods for dispersing seeds away from the parent plants and for spreading out the potential offspring populations. This reduces direct competition between the next year’s seedlings and between the seedlings and the parent plants, and it facilitates population expansion into new areas. Many plants are dispersed by animals that eat the fruit or store the fruit for future use; fruits of other plants are dispersed by wind or water. The little, prickly seeds of rattlesnake weed are very effective hitchhikers, grabbing a ride in the fur of animals, the feet of birds or, more recently, the clothing of humans.

In spite of the seemingly endless number of times that we have to de-burr our pets or our socks, hitchhiking is not a common method of seed dispersal. It is estimated that only 5% of plants have evolved this strategy, and these are mainly plants within the Carrot family (Apiaceae), like rattlesnake weed, or within the sunflower family (Asteraceae). The poster child for a plant hitchhiker may be cocklebur (Xanthium straminarium) whose tenacious hooks were the inspiration for Velcro™.

tiny seed pods on sweater

Santa Carina trailhead | May 2017

view of single white flower pod

Two-chambered dry fruit | Rios trailhead | May 2017

tiny white flowers with red interior

Close-up of mature fruit | Santa Carina trailhead | May 2017

Human Uses  

There are scattered reports of native Americans using rattlesnake weed as a treatment for rattlesnake bites; either a decoction was swallowed or a poultice of the chewed plant was applied directly to the wound.15,59,282 It does not appear, however, that the effectiveness has been confirmed.59 Other records describe the use of the roots as food, either fresh or cooked.282

Locally, the Kumeyaay boiled the whole rattlesnake weed into medicine for fevers or toothaches.16 The Chumash Indians of Santa Barbara and the Channel Islands may have used it for rattlesnake bites, as well as in snake charming rituals, but the reports may have confused our rattlesnake weed and the related biscuit root (Lomatium californicum).15

Extreme care must be taken not to mistake poison hemlock (Conium maculatum) for rattlesnake weed. Poison hemlock is similar in appearance but is one of the most deadly plants in North America.41,143 Those that have made that mistake have not had happy endings.56

tiny white flowers with red parts

Close-up of mature fruit | Santa Carina trailhead | May 2017

tiny white flowers under microscope

Close-up of flowering umbel | Santa Carina trailhead | April 2017

plant with small white flower pods on top of stems

Santa Inez trailhead | May 2011

Interesting Facts 41,338,339

Rattlesnake weed is closely related to Queen Anne’s lace (Daucus carota), from which the garden carrot was derived.The original wild carrot did not have the typical carrot taproot, and It is thought that it was first domesticated for medicinal purposes, probablybetween 2000 and 3000 years ago. The carrot with the taproot we know today was developed about 600 AD. The first roots were purple. Orange carrots were produced in Holland in the 17th Century, to celebrate the Royal House of Orange. From Holland, they were brought to the Americas. Carrots are now grown worldwide.

green plants with small white flowers on top of stems

Santa Carina trailhead | April 2017

leaf with many different parts

Pinnately divided leaf | Santa Carina trailhead | May 2017

tiny white flowers bunched together

Rios trailhead | April 2017

Photo Gallery