Grassy Tarweed
Madia gracilis
NATIVE
Description (Jepson, PlantID.net)
- Eudicotyledon
- Eudicots are a major lineage of flowering plants; see family for general characteristics
- Sunflower Family (Asteraceae)
- Annual herb
- Whole plant hairy, with gland-tipped (sticky) hairs on upper stems and leaves
- Strongly aromatic
- Leaves
- Blades oblong to linear and hairy
- Lower leaves opposite (2 leaves at each junction with stem)
- Upper leaves alternate (1 leaf at each junction with stem), some with gland-tipped hairs
- Flowers
- Inflorescence (flower arrangement) in open clusters of yellow radiate flowerheads (see Sunflower family), each head with two kinds of flowers
- Ray flowers (3-8) are lemon yellow and female (pistillate)
- Disk flowers (5-22) are yellow-green and bisexual, with black-brown anthers (pollen-producing parts)
- Phyllaries (vase-like floral bracts, collectively called the involucre) are urn-shaped, hairy, and densely glandular (sticky)
- In a single series (row), one for each ray flower
- Ovary inferior (below the attachment of other flower parts)
- Inflorescence (flower arrangement) in open clusters of yellow radiate flowerheads (see Sunflower family), each head with two kinds of flowers
- Each ovary is enfolded, pocket-like, by a phyllary
- Fruit is an achene (a single-seeded, dry fruit that does not split open), more specifically called a cypsela because of the inferior position of the ovary
- Disk-flower fruits are held together in a cup created by a set of fused, chaffy bracts (paleae)
- Height to 39 in.
Distribution
- Native to California
- Grows in many habitats including open, semi-shaded, or disturbed sites
- See Calflora for statewide observations of this plant
- Outside California, grows across Western North America, from British Columbia into Baja California, Mexico, and into Montana and Utah
- Grows at elevations to 8,200 ft.
Uses (San Mateo County Parks prohibits removal of any natural material)
- Wildlife
- Birds and small mammals feed on the seeds
- Seeds provide food for small mammals, e.g. mice, and numerous birds, e.g. mourning dove (Zenaida macroura), California quail (Callipepla californica), California towhee (Melozone crissalis), and dark-eyed junco (Junco hyemalis)
- Frequented by insects for pollen and nectar
- Host (food source for the larval stage) for small heliothodes moth (Heliothoides diminutiva)
- Birds and small mammals feed on the seeds
- Native people
- Seeds of tarweeds (Hemizonia and Madia species), which are abundant, aromatic, and rich in oil, were a prized component of pinole for many California native peoples (Lowry 2009)
- Pinole is a general term for various flours made from the ground, toasted seeds of wildflowers and grasses, eaten dry or moistened and shaped into balls or cakes (Anderson 2005)
- “Pinole” is a Hispanic version of an Aztec word
- Harvesting, done by women moving across fields and beating seeds into baskets, could occur before or after fields were burned to stimulate regrowth (Anderson 2005; Williams 2003)
- If fields were burned before harvesting, the seeds were already roasted when beaten from the scorched, still-standing, but no longer sticky plants (Williams 2000)
- Seeds of tarweeds (Hemizonia and Madia species), which are abundant, aromatic, and rich in oil, were a prized component of pinole for many California native peoples (Lowry 2009)
Name Derivation
- Madia (MAD-ee-a) – from the Chilean native name madi, used to refer to the coast tarweed, Madia sativa
- gracilis (GRAS-il-is) – from the Latin, meaning “slender” or “graceful”
- Tarweed – from the sticky nature of the tar-like oils of mature plants
Adaptations
- Well-adapted, like most tarweeds, to flower and fruit during our Mediterranean climate’s long dry summers and autumns (Lowry 2009)
- Develops deeper roots than most annuals to capture ground water before bolting
- Resinous glands on the tips of trichomes (plant hairs) increase humidity
- Mucilage (a thick, gluey substance) in stems and leaves retains moisture
- Late-summer blooming ensures few competitors for pollinators
- Ray-flower fruits are each enfolded by a glandular (sticky) phyllary, aiding in the seed’s dispersal by catching onto passing animals
- Terpenes, a group of chemical compounds exuded from glands, deter herbivory (Grenada 2017)
- Cattle enjoy young plants, but eschew mature, highly glandular plants, causing some ranchers to kill tarweeds (Lowry 2009)
- Terpene-exuding glands also provide an indirect defense against herbivory
- Glandular plants are visited by various large and small herbivorous insects
- Smaller insects, e.g., aphids and small flies, are trapped by the sticky glands and attract predatory insects, e.g., the spine-collared assassin bug (Pselliopus spinicollis)
- Predatory insects also eat larger visiting insects, e.g., some weevils and mealybugs, and the small heliothodes moth caterpillar (Heliothodes diminutiva), that would otherwise eat the tarweed
- In a controlled study, UC researchers found that hayfield tarweed and common madia plants with trapped insects produced more flowers and seeds (LoPresti 2017)
- Watch this short video showing the assassin bug in action (KQED 2021)
Notes
- The Tarweed-Silversword subtribe (Madiinae) includes some 127 species, principally in California, where it likely originated, and Hawaii (Flora; Baldwin 2000)
- California’s tarweeds are traditionally called “true tarweeds”
- Most are summer-flowering annuals in summer-drought habitats
- Leaves and phyllaries are usually hairy and glandular
- Most species have radiate heads of yellow or white flowers
- Each phyllary cups or encloses a single ray flower
- Anthers are usually dark
- Chaffy bracts usually create a ring between the ray and disk flowers
- Edgewood has 10 tarweeds in 5 genera
- Achyrachaena species: blow-wives (A. mollis)
- Hemizonia species: hayfield tarweed (H. congesta ssp. luzulifolia)
- Lagophylla species: common hareleaf (L. ramosissima)
- Layia species: tidy-tips (L. platyglossa), tall layia (L. hieracioides), and woodland tidy-tips (L. gaillardioides)
- Madia species: common madia (M. elegans), threadstem tarweed (M. exigua), slender tarweed (M. gracilis), and coast tarweed (M. sativa)
- California’s tarweeds are traditionally called “true tarweeds”
- The scent of slender tarweed is often described as pleasingly citrus-like
ID Tips
- May be confused with coast tarweed (M. sativa), tall layia (L. hieracioides), or common hareleaf (L. ramosissima), all of which are also in the Tarweed subtribe (Madiinae) and have similar flowers
| Common Hareleaf | Slender Tarweed | Tall Layia | Coast Tarweed | |
| Height | ≤ 40 in. | ≤ 40 in. | ≤ 50 in. | ≤ 100 in. |
| Stems | not glandular (sticky) … dark, wiry | upper stems glandular (sticky) … green | glandular (sticky) … green | densely glandular (sticky) … green |
| Leaves | upper leaves sometimes glandular (sticky) | upper leaves glandular (sticky) | glandular (sticky) | densely glandular (sticky) |
| Flower Clusters | open or dense | open | open | dense |
| Flower Color | pale yellow | lemon yellow | yellow | yellow |
| Scent | negligible | pleasant | sweet or pungent | pungent |
| Blooming Season | late spring – early fall | spring | spring | summer |
At Edgewood
- Found in grasslands
- See iNaturalist for observations of this plant
- Flowers May – July
Specific References
Anderson, M.K. 2005. Tending the Wild. University of California, Berkeley.
Baldwin, B.G., and B.L.Wessa. 2000, Dec.1. Origin and relationships of the tarweed-silversword lineage (Compositae-Madiinea). American Journal of Botany.
California Native Plant Society Yerba Buena Chapter. The tarweeds.
Granada Native Garden Newsletter. 2017, Oct. 15. Tarweeds — and their evil cousin!
KQED San Francisco. 2021, Sept. 8. You can’t unsee the assassin bug’s dirty work [Video]. Deep Look. YouTube.
LoPresti, E., B. Krimmel, and I. Pearse. 2017, Dec. 20. Entrapped carrion increases indirect plant resistance and intra-guild predation on a sticky tarweed. Abstract. OIKOS.
Lowry, J.L. 2009, July 1. The scent of summer. Bay Nature.
Prigge, B.A., and A.C. Gibson. 2013. Madia gracilis. A Naturalist’s Flora of the Santa Monica Mountains and Simi Hills, California. Web version, hosted at Wildflowers of the Santa Monica Mountains National Recreation Area. United States Department of Interior, National Park Service.
Ross, T., and A. Bartow. 2012. Grassy tarweed Madia gracilis (Sm.) D.D. Keck. Plant Guide. United States Department of Agriculture, Natural Resources Conservation Service, Plant Materials Center, Corvallis, Oregon.
Williams, G. W. 2000. Early fire use in Oregon. Fire Management Today 60(3): 13-20.
Williams, G. W. 2003. References on the American Indian use of fire in ecosytems. Intertribal Timber Council.
General References
Calflora Database. 2014. Berkeley, California.
Calscape. 2018. California Native Plant Society.
Charters, M.L. 2015. California Plant Names: Latin and Greek Meaning and Derivations.
Charters, M.L. 2017. Southern California Wildflowers: Guide to the Pronunciation of Specific, Generic and Family Names.
Corelli, T. 2004. Flowering Plants of Edgewood Natural Preserve (2nd. ed.). Monocot Press, Half Moon Bay, California.
Flora of North America. efloras.org.
Harris, J.G., and M.W. Harris. 2013. Plant Identification Terminology: An Illustrated Glossary. Spring Lake Publishing, Spring Lake, Utah.
Native American Ethnobotany DB.
Regents of the University of California. Jepson eFlora. Jepson Herbarium. University of California, Berkeley.