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     The genus Grindelia was described in 1807 by Willdenow, based on specimens of Grindelia inuloides that were grown in the Royal Botanical Garden in Berlin. These plants were grown from seed collected in Mexico by Humboldt and Bonpland.

     The three species pictured on this page are commonly called "Gumweed" because of their very sticky phyllaries. "Grindelia" honors David Hieronymus Grindel, Russian chemist, pharmacist, and doctor.  (Click for more biographical information about Grindel.)

Grindelia arizonica
Grindelia arizonica
Grindelia arizonica (Arizona Gumweed)
Asteraceae (Sunflower Family)

Foothills. Openings. Summer, fall.
Above: Ridge South of Dolores, August 28, 2021.
Left: Prater Ridge Trail, Mesa Verde National Park, August 13, 2005.

Grindelia arizonica typically grows several feet high and wide in a bushy shape with numerous bright yellow flowerheads which often have fairly erect ray flowers. Grindelia flowers exude a strange and strong medicinal smell, the product of their glandular, very sticky hairs. Stems of G. arizonica are often red. The toothed leaves are well-space along the stem giving the plant its characteristic open appearance.

Grindelia arizonica

Grindelia arizonica

Grindelia arizonica (Arizona Gumweed)
Asteraceae (Sunflower Family)

Foothills. Openings. Summer, fall.
Ridge South of Dolores, August 28, 2021 and Prater Ridge Trail, Mesa Verde National Park, August 13, 2005.

The very prominent phyllaries (the green overlapping structures below the yellow ray flowers) are sticky, in four or five rows, and, in this species, are vertical and pressed against the main floral body, not, or only moderately curved back at the tips. (Compare these phyllaries with those of G. squarrosa below.)

Grindelia arizonica

Grindelia arizonica (Arizona Gumweed)
Asteraceae (Sunflower Family)

Foothills. Openings. Summer, fall.
Ridge South of Dolores, August 28, 2021.

Leaves of G. arizonica are variable: they are oblong to oblanceolate to ovate-lanceolate to spatulate. They are entire to slightly dentate to pinnately lobed. They are said to be sessile and not clasping, but in the photograph at left you can see that some leaves are clasping. Plants naturally often have variable characteristics. In this case we may be seeing the result of hybridization with Grindelia decumbens, a species found in New Mexico.

 

Grindelia hirsutula
Grindelia hirsutula.  Synonym: Grindelia fastigiata. (Hairy Gumweed)
Asteraceae (Sunflower Family)

Semi-desert. Openings. Summer, fall.
Hunter Canyon, Utah, September 26, 2005.

Grindelia hirsutula grows to four feet tall in sand or clay soils in dry open places and along washes, as in the photograph at left. This species is just as sticky and aromatic as the other Grindelias shown on this page. G. hirsutula hybridizes with G. squarrosa.

Although ray flowers are present on this species in many areas, in the Four Corners region the plant often has no ray flowers.

"Hirsute" is Latin for "hairy" and "hirsutula" is "a little hairy". (Botanically, "hirsute" means "clothed with coarse, stiff hairs".) "Fastigi" is Latin for "pointed", perhaps referring to the sharply pointed bracts and/or to the pointed appearance of the disk flowers as shown in the photograph below.

The name of this species is controversial. Weber accepts it at species status but does not accept G. fastigiata; Ackerfield accepts both (with three varieties of G. hirsutula); Kartesz indicates that G. fastigiata is rare in the Four Corners region and that G. hirsutula is a species found only in far western California, never in the Four Corners states; Welsh accepts only G. fastigiata and says G. hirsutula is a synonym; Flora of the Four Corners Region does not indicate that either species exists in the Four Corners region; and Flora Neomexicana III indicates that G. hirsutula is found in a very limited area of north central New Mexico.

The Flora of North America provides a detailed analysis of all the various species (click to read) and indicates, 

Grindelia hirsutula includes 30 or more reputedly distinct, local, regional, or ecotypic [taxa] that have been named at species or infraspecific rank. Locally, such [taxa] are easily recognized; in a broad view, they intergrade with other [taxa] and are parts of a heterogeneous continuum. Taxonomies that have attempted to recognize the [taxa] as distinct "taxa" have led to almost as many specimens determined as "intermediate" as are assigned to the named "taxa."

FNA includes G. fastigiata among the 30 taxa mentioned above. In other words, the FNA does not accept G. fastigiata as a distinct taxon.

Grindelia hirsutula was named and described by William Jackson Hooker and George Arnott in 1833, from collections made by Lay and Collie on the 1825-1828 Beechey Expedition.

Grindelia hirsutula
Grindelia hirsutula. Synonym: Grindelia fastigiata. (Hairy Gumweed)
Asteraceae (Sunflower Family)

Semi-desert, foothills. Openings. Summer, fall.
Hunter Canyon, Utah, September 26, 2005 and Arches National Park, Utah, May 27, 2016.

                                 Grindelia hirsutula

 

Grindelia nuda

Grindelia nuda

Grindelia nuda

Grindelia nuda. Synonyms: Grindelia squarrosa, Grindelia aphanactis. (Rayless Gumweed)
Asteraceae (Sunflower Family)

Foothills. Openings, shrublands, woodlands, disturbed areas. Summer, fall.
Durango West II Natural Areas, August 24, 2021.

Flower heads of Grindelia nuda have only disc flowers; there are no ray flowers. In this and many other respects G. nuda is similar to G. squarrosa, and in fact, several floras (including the FNA, BONAP, and Colorado Flora) consider this taxon to be G. squarrosa. It is accepted as a distinct species by the Flora of the Four Corners Region and the Flora of Colorado, but these two floras do not agree on a number of significant morphological characteristics of G. nuda.

Baker, Earle, and Tracy were the first to collect this species for science in 1898 in Durango, and in 1904 Rydberg described it and named it Grindelia aphanactis. Guy Nesom renamed it Grindelia nuda variety aphanactis in 1990, returning it to the specific epithet (nuda) that Alphonso Wood had given it in the mid-1800s. I cannot provide a BONAP map for G. nuda since BONAP considers it to be the same species as G. squarrosa, but other sources indicate that this taxon is found across the southern section of the West and is found scattered through the lower elevations and foothills of the Four Corners region.

Grindelia nuda

Grindelia nuda

Grindelia nuda. Synonyms: Grindelia squarrosa, Grindelia aphanactis. (Rayless Gumweed)
Asteraceae (Sunflower Family)

Foothills. Openings, shrublands, woodlands, disturbed areas. Summer, fall.
Durango West II Natural Areas, August 24, 2021.

Leaves are much longer than wide, dark green, sometimes clasping the stem, and often toothed.

Stems are smooth ("glabrous") and vary from almost white to green to red. Stems crisscross, and as all the photographs show (especially the top photograph in this section), this gives the shrub-like plant an interlaced, messy appearance.

Phyllaries are moderately to strongly recurved, sometimes bending backwards into a circle.

 

Grindelia squarrosa
Grindelia squarrosa (Curly Gumweed)
Asteraceae (Sunflower Family)

Foothills. Openings. Summer, fall.
Dolores River Canyon, August 20, 2005.

Stems of G. squarrosa are usually green, not red, and leaves are more serrated than in G. arizonica.

Meriwether Lewis was the first to collect this plant for science. He collected it on the banks of the Missouri River, near Tonwontonga, Nebraska, August 17, 1804. Click to see Lewis' specimen. Frederick Pursh named the new species Donia squarrosa in 1814.  It was renamed Grindelia squarrosa by Dunal in 1819.

Grindelia squarrosa
Grindelia squarrosa (Curly Gumweed)
Asteraceae (Sunflower Family)

Foothills. Openings. Summer, fall.
Dolores River Canyon, August 20, 2005.

From a distance, the species of Grindelia pictured on this page are very similar looking.  A close look shows that a most noticeable difference is in the curving of the phyllaries.  The arching ("recurved") phyllaries of G. squarrosa are prominent and key to identifying this species.

Several floras, including the Flora of North America, indicate that G. squarrosa can sometimes be found without ray flowers. Other floras, such as, Ackerfield's Flora of Colorado indicate that this species always has ray flowers and that the rayless Grindelias are G. fastigiata or G. nuda, neither of which are accepted as species by FNA.

"Squarrosa" is Latin for "scaly or rough", but botanically means "recurved", i.e., curved backwards. This recurved shape would, of course, make the phyllaries feel scaly or rough. 

 

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Range map for Grindelia arizonica  

Grindelia fastigiata

Range map for Grindelia fastigiata. This name is considered a synonym by the Flora of North America. The taxon is included in G. hirsutula. See the note immediately below and the discussion above.

Grindelia hirsutula

Range map for Grindelia hirsutula (Range according to Kartesz, but FNA places G. hirsutula in all western states and more. Click to see map.)

Range map for Grindelia squarrosa