Gumplant

Grindelia camporum

yellow gum plant flowers
Stonebridge Mesa | June 2017

Gumplant (Grindelia camporum) is not an especially attractive plant, but it has a quirky charm. It is a tall, rangy plant that thrives during the hot summer months when the yellow, daisy-like flowers are an important pollen source. The plant, especially the flower buds, are covered with a sticky, milky substance that gives the plant its name. This gum is thought to protect against herbivores and also against damage from ultra-violet radiation.

Native Americans used gumplant to treat lung problems and skin infections. It is still widely used by herbalists today for pulmonary problems such as bronchitis, whooping cough, hay fever and emphysema.

Other Common Names:

Common gumweed, San Diego gumplant, White-stem gumplant, Great Valley Gumweed, Resinweed

Description 11,26,34,59,67,306

Gum plant is a highly variable species with many local forms. Descriptions in the literature are often based on local populations may differ more than usual from each other and from ours.

Gumplant is a gangly plant, with open branching to about four feet. Leathery leaves are obovate to oblanceolate, somewhat waved, with variable margins, often sharply serrate occasionally nearly untoothed. Basal leaves are usually less than six inches long with a blade that tapers to a winged petiole. Cauline leaves are smaller and lack petioles; the leaf base clasps the stem, often with two small basal wings. The entire plant is glandular and highly resinous, but this is most conspicuous in the developing flower heads.

Yellow daisy-like flower heads are held in open clusters, each flower at the end of a stem-like peduncle. The base of the flower head is hemispheric to flattened globose, with several layers of overlapping phyllaries. Phyllaries are linear with the tips strongly recurved. Phyllaries have numerous glands that produce copious amounts of white, gummy substance that coats the unopened flower head, making it glisten.  Flower heads appear in late summer and consist of  yellow ray florets surrounding a dense “eye” of many yellow disk florets. Ray flowers lack stamens. The single ovary is inferior with one two-branched style that extends slightly beyond the corolla tube. Disc flowers have a tubular lobed corolla and five or six stamens with the anthers united into a tube around the two-branched style. Flowers can usually be found between May and July although flowers in Nov. have been reported.468

Each fertilized floret produces a one-seeded fruit. The pappus is reduced to one to three small, easily-detached bristles; these resemble tiny porcupine quills and their function is unknown.

yellow-flowered gum plant

Stonebridge Mesa | June 2011

Daisy-like gum plant flower

Stonebridge Mesa | June 2011

seed head

Seed head | Stonebridge Mesa | Oct. 2019

Distribution 7,26,34,67,468

Gumplant is a California native most common below 4000 ft in the Central Valley, in the San Francisco Bay area and along the southwestern coast into northern Baja. It is found in a variety of habitats – dry slopes and fields, clay or sandy roadsides, stream banks and dry washes in chaparral and coastal sage scrub. It thrives in hot dry climates.

In the Reserve, gumplant is found primarily on Stonebridge Mesa. It can be quite abundant, but often blooms among masses of yellow tarplant (Deinandra fasciculata ) which neatly camouflages the gumplants.

Reserve map of chaparral, coastal sage scrub and grassland

Classification

Gumplant is a dicot angiosperm in the sunflower family, the Asteraceae.2 This is the largest family of vascular plants in the Northern Hemisphere.143 “Flowers” of Asteraceae are made up of one or both of two types of flowers (florets): symmetrical disk florets and strapped-shaped ray florets. These are crowded onto a common base (receptacle), and together are often assumed to be a single flower, which we call a flower head.11,44,49

There are more than 75 species of  Asteraceae reported from the Reserve.48 Native species include such diverse species as sea dahlia (Leptosyne maritime), coyote brush (Baccharis pilularis), California sagebrush (Artemisia californica), yellow pincushion (Chaenactis grabriuscula), and cobwebby thistle (Circium occidentale).

The genus Grindelia is a highly variable array of ecological forms from diverse habitats over a large area in America.67 The most recent (1934) treatment of the genus established many species that botanists today regard as subspecies, varieties and local races. 67,306  Some of these are accepted by some botanists, others have been regrouped into larger taxa.

Many descriptions in the literature of G. camporum differ considerably from our plants. I have relied on the experienced botanists who have examined our Reserve plants and determined them to be G. camporum. This taxonomy follows the current generic treatment by Jepson7 (our accepted authority) but differs from that of Flora of North America306 which unites 30 of our more  distinct local populations that have been described at a species or intraspecific rank (including G. camporum) into one variable species, G. hirsutula.

Alternate Scientific Names:

Grindelia robusta, G. hirsutula

Jepson eFlora Taxon Page
field of gum plant and tarweed

Stonebridge Mesa | June 2019

Daisy-like gum plant flower

Stonebridge Mesa | June 2017

section of seed head

Seed head; left to right, lines show pappus, corolla, developing fruit | Stonebridge Mesa | Oct. 2019

Ecology

There are reports that the resin of gumplant serves to deter grazing insects67 and also that it protects the buds from strong sunlight.23,34
The latter function has recently received support from research on a related gumplant in Patagonia.502 The resin, which has similarities to pine resin, absorbs in the UV-B spectrum of sunlight. In the presence of UV-B, gumplant increases its production of resin. At the same time, the presence of UV-B appears to reduce both plant height and biomass.

field of yellow gum plants

Stonebridge Mesa | June 2011

Flower bud

Unopened bud | Stonebridge Mesa | June 2016

close-up of flower base

Glandular phyllaries | Stonebridge Mesa | Oct. 2019

Human Uses

I have found no reports that the local Indians, the Kumeyaay, used gumplant, but other California tribes used several species of gumplant interchangeably for medicinal purposes. They drank a tea or decoction of stems, leaves and buds as treatment for respiratory ailments such as asthma, bronchitis and whooping cough.15,23,34,503 For skin problems, especially poison oak, the resin from the plant tops was applied directly or made into a wash. There is one report503 that the buds were chewed like gum; the writer tried it and “it wasn’t pleasant”.

Today, Grindelia may be found in herbal remedies, where it is mainly used for its anti-inflammatory, expectorant, sedative and pain-relieving properties.67,92,503 At present, there is insufficient evidence to judge its effectiveness.482

field of gum plant

Stonebridge Mesa | May 2016

gum plant flower

Flower head with recurved phyllaries | Stonebridge Mesa | June 2017

clump od gum plant leaves

Basal rosette | Stonebridge Mesa | May 2016

Interesting Facts

In California, the common names for this plant are versions of “gumplant” “gumweed” and “resinweed” – not likely  to stimulate visions of bouquets. The early Spanish saw things more romantically and called it Boton de Oro  or “golden button”.67

gangly gum plant with yellow flowers

Stonebridge Mesa | June 2017

yellow gum plant flower

Flower head and unopened bud | Stonebridge Mesa | June 2017

Daisy-like gum plant flower with bee

Stonebridge Mesa | June 2011

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