Index | Search | Home

New Crop FactSHEET

Grindelia

Contributor: Steven P. McLaughlin, Office of Arid Lands Studies, University of Arizona.

Copyright © 1995. All Rights Reserved. Quotation from this document should cite and acknowledge the contributor.


  1. Common Names
  2. Scientific Names
  3. Uses
  4. Origin
  5. Crop Status
  6. Botany
    1. Taxonomy
    2. Morphology
    3. Resin Chemistry
    4. Reproductive Biology
  7. Crop Culture
    1. Agronomy
    2. Harvesting and Processing
  8. Germplasm
    1. Key References
  9. Selected Experts

Common Names

English: gumweed
Spanish: boton de oro

Scientific Names

Species: Grindelia camporum Greene var. camporum
Family: Asteraceae (Compositae)

Uses

The resins produced by Grindelia consist mostly of labdane-type diterpenoid resin acids, similar in chemistry and physical properties to those obtained from pine trees for use in the "naval stores" industry. Resins from various species of Grindelia have been patented for use in adhesives, rubber, coatings, textiles, and polymers. Grindelia resins could provide a potential alternative source of diterpene resin acids for use in inks, sizings, adhesives, tackifiers, and other naval stores products.

Origin

Grindelia camporum var. camporum is native to the San Joaquin Valley, Sacramento Valley, and adjacent Coast Ranges of Central California. It is one of the few plants in this area of winter rainfall to grow and flower primarily in the hot, dry summer months.

Crop Status

Grindelia camporum var. camporum has been grown experimentally in Arizona and in Pakistan. Investigations on the agronomy and resins of South American species are currently underway in Argentina and Chile.

Botany

Taxonomy

There are approximately 40-60 species of Grindelia native to temperate, mostly arid and semiarid regions of North and South America. The basic chromosome number is x=6; diploids (2N=12), tetraploids (4N=24), and hexaploids (6N=36) are known. Species of Grindelia are often poorly differentiated and the taxonomy of the genus is still poorly understood. Tetraploid forms of G. camporum have traditionally been recognized as G. camporum var. camporum; diploid forms encompass several named taxa. The most recent taxonomic treatment lumps several distinct forms, including diploid G. procera, into G. camporum var. camporum.

Morphology

Grindelia species include annuals, biennials, herbaceous perennials, and shrubs. G. camporum var. camporum is an herbaceous perennial. It initially produces a basal rosette of leaves which soon bolts to produced several branched, flowering stems 60-200 cm tall. The leaves are shiny, entire or serrate, and 2-6 cm long. The capitula consist of fertile, yellow ray and disk florets with 2-6 short awns. Resin is produced in sessile, multicellular, densely-staining glands found on the involucre bracts, leaves, and stems. Density of resin glands is highest on the involucre bracts and lowest on the stems. Thus the highest crude resin yields are found in the flower heads (ca. 20%) and the lowest yields are from the stems (ca. 2%); leaves yield ca. 14% crude resin. There is significant variation between populations of G. camporum var. camporum (grown in a common-garden environment) in phenology, biomass production, leaf and flower morphology, and resin yield. Crude resin yields are highest (ca. 15%, based on individual plant analyses) in plants from populations in the northernmost part of the species' range in California.

Resin Chemistry

Grindelic acid is the primary component of the resin in most species of Grindelia in North and South America. Derivatives of grindelic acid that occur with a lower percentage yield include 17-acetoxygrindelic acid, 6-oxo-grindelic acid, 13-isogrindelic acid, 7,8-epoxygrindelic acid, and strictanoic acid. In G. acutifolia and occasional collections of a few other Rocky Mountain species, 17-methoxygrindelic acid and 17-acetoxygrindelic acid are the major components, while 17-acetoxygrindelic acid is the major component in the resin of G. subalpina. It is not yet known how variation in resin chemistry affects physical properties of the resin. Grindelia havardii of Texas and G. discoidea of Argentina produce labdanoids lacking the tetrahydrofuran ring that is characteristic of grindelic acid and its derivatives.

Reproductive Biology

Grindelia camporum var. camporum is self-incompatible. Hand pollinations between plants from different populations showed that all populations were fully compatible. In these hand-pollination studies achene yields ranged from 21-71 per capitulum. Individual florets remain open for one day. Anthesis in the capitulum is centrifugal with ray florets opening last. Achenes mature approximately 22 days after pollination and are fully dispersed 53 days after anthesis. Mean achene weight is 430 g-1.

Crop Culture

Agronomy

Grindelia camporum var. camporum was selected for agronomic development because it appeared to represent the best combination of biomass production, resin yield (10-15% crude resin), and drought tolerance of all of the North American species. Grindelia glutinosa and G. tarapacana from Chile have been reported to have higher crude resin yields, 17% and 26%, respectively.

Arizona field trials were initiated with transplants since the achenes proved to have a light requirement for germination. Research in Pakistan found high rates of germination in soil for seeds planted at shallow depths (1-3 mm) when the soil was kept constantly moist. Optimum planting density is approximately 80000 plants/ha. Stands planted in Arizona in October could be harvested in late June and again in late September producing a total yield of 12.5 Mg DW/ha/y with an average crude resin yield of 9.4%. In field trials at Lahore, Pakistan, G. camporum var. camporum produced a total biomass yield of 13.6 Mg DW/ha/y from two harvests; crude resin yield was also 9.4%. The Arizona plots were irrigated with 67 cm of water; plants in Pakistan received just 33 cm.

Harvesting and Processing

Plants can be cut and windrowed in the field to dry for 2-5 days. Air-dried plant material is then hammermilled with a 4 mm screen and stored pending extraction. The crude resin can be obtained by solvent extraction with a polar solvent such as cyclohexane or dichloromethane. Yields obtained in the laboratory from individually harvested plants appear to be 2-3% higher than yields observed from samples of bulked, field-dried, hammermilled plants. Lost of leaf material during collection and handling, and loss of finer, resin-rich material during hammermilling may account for this difference.

Germplasm

No germplasm collections of Grindelia are currently being maintained.

Key References

Selected Experts

Joseph J. Hoffmann, Bioresources Research Facility, Office of Arid Lands Studies, University of Arizona, 250 E. Valencia Rd., Tucson, AZ 85706. Tel: 520-741-1691; FAX: 520-741-1468; Email: jjhoff@ccit.arizona.edu.

Steven P. McLaughlin, Bioresources Research Facility, Office of Arid Lands Studies, University of Arizona, 250 E. Valencia Rd., Tucson, AZ 85706. Tel: 520-741-1691; FAX: 520-741-1468; Email: spmcl@ag.arizona.edu.

Contributor: Steven P. McLaughlin, Office of Arid Lands Studies, University of Arizona.

Copyright © 1995. All Rights Reserved. Quotation from this document should cite and acknowledge the contributor.


Last update Tuesday, February 24, 1998 by aw