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Vernonia

Contributor: David A. Dierig

Copyright © 1997. 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. Toxicities
  7. Botany
    1. Taxonomy
    2. Morphology and Floral Biology
  8. Ecology
  9. Crop Culture
  10. Germplasm
  11. Key References
  12. Selected Experts

Common Names

vernonia

Scientific Names

Species: Vernonia galamensis (Cass.) Less. In Linnaea 4:314 (1829)

a. subsp. galamensis
1. var. galamensis
2. var. petitiana (A. Rich.)
3. var. australis
4. var. ethiopica
b. subsp. nairobensis
c. subsp. lushotoensis
d. subsp. mutomoensis
e. subsp. afromontana (R.E. Fries)
f. subsp. gibbosa

Before a taxonomic revision of the complex, this species was referred to in earlier literature as Vernonia pauciflora (Pursh.) Poir. An earlier and less common name for this species was Conyza pauciflora Willd.

Family: Asteraceae or Compositae

Uses

Seeds from this plant contain an oil rich in epoxy fatty acids. Epoxy oils are widely used in plasticizers and additives in flexible polyvinyl chloride (PVC) resins. This market is supplied by the epoxidation of either soybean or linseed oil. The composition of vernonia oil has superior qualities compared to these other oils. A potential market use might be as a drying agent in reformulated oil-based or alkyd-resin paints. Some 325 million gallons of paint are manufactured annually in the U.S. The drying agents currently used are major pollutants. One study showed that in Los Angeles area alone, as much as 22 tons per day of volatile organic compounds (VOCs) are released into the air from paints and varnishes. Vernonia has 'reactive dilutant' oil properties that reduce these pollutants. Other uses for the oil could be in the manufacture of new types of plastics called interpenetrating plastics. The oil can also form clear, tough, rubbery plastics or coatings on metal.

Origin

About 1000 species are found in the large genus Vernonia. The species V. galamensis is limited in distribution to primarily Eastern Africa (at present, one variety has been found in Western Africa). Another species, V. anthelmintica, originating from India, also contains high amounts of vernolic acid in the seed-oil. Attempts to domesticate this India species ended when seed shattering before harvest could not be controlled. A closely related genus, also within the taxonomical tribe of Vernonieae, Stokesia aster, native to the Southeastern U.S., also contains vernolic acid. Domestication attempts have been made but since it is a perennial plant it is not a promising candidate.

Crop Status

The annual plant is grown on small farms in Africa where seeds are bought and crushed for oil locally. Private industries have also grown this species in other countries located close to the equator. This is because the plants with the largest seed and best seed retention only flowers under short-day conditions (winter in the U.S.). These botanical varieties will not grow in the U.S. because they are frost sensitive.

New hybrids were developed at the U.S. Water Conservation Laboratory, Phoenix, Arizona between these short-day flowering types and an accession flowering under any day length. These day-neutral hybrids can be planted in February or March and harvested in September or October (long-day conditions). They have been successfully grown in Arizona, Kentucky, Missouri, Oregon, Texas, Virginia and Northern Argentina. Commercial development of these hybrids depends on further improvement of seed yields.

Toxicities

Unknown but pollen is allergenic.

Botany

Taxonomy

Size and form of the phyaries, pollen and fruit, and pappus morphology have been used to define sections within Vernonia. Other annual species of Vernonia appear to be unrelated. Workers acknowledge that there is a striking range of variation even within botanical varieties. A 'split' approach was adopted in the revision of the taxonomical treatment by Gilbert (1985) because of the interest in the species as a potential oilseed crop.

Morphology and Floral Biology

The flower head (capitula) are very variable in size. The petals that surround the seeds on the capitula (involucre) through maturity, range between eight and 25 mm long. The colors of the florets (individual flowers that makes up the capitula) are either blue to purple, or white. The capitula is made up of 50 to 150 florets. This roughly corresponds to the number of seed produced per capitula, depending on pollination events. Hairs attached to the seed (pappus) can be up to 8 mm long. Chromosome counts of accessions are 2n = 18. Subspecies readily hybridize among themselves.

Ecology

All of the taxa, except for a few accessions of V. galamensis spp. galamensis var. petitiana, are short-day plants. Most plants will flower after receiving five to 10 short days of 11 h light and 13 h dark periods. Those accessions of var. petitiana will flower any time of the year, although more flowers are produced under short days. Plants flower indeterminately.

Crop Culture

Little information is available on cultural management of day-neutral vernonia hybrids since only small research plots have been grown in the U.S. Larger production fields of short-day accessions have been grown in Zimbabwe, and other African and Central American countries near the equator. Seed yields from 1345 kg/ha in 1985 to 2494 kg/ha in 1987 have been reported from those countries.

A planting density study at Maricopa, Arizona was made in 1994 with hybrid lines by varying plant spacing within rows, which were 1 m apart. Plant populations were established at 15,000, 30,000, and 60,000 plants/ha using spacing of 0.60, 0.30, and 0.15 m, respectively. Although plants flowered earlier in the 0.60 m spacing, these plants appeared to be the poorest performers toward the end of the season. As plants mature, the stems become brittle. There is an advantage to space plants closer to provide support each other. The closer spacing may also force flowering on the top and outside canopy, achieving better plant architecture for harvesting. The planting rates of the three spacings were 4, 8, and 12 kg/ha respectively.

Field planting and harvesting can be accomplished using existing farm equipment, such as a grain drill for planting and a combine for harvesting. Further agronomic research is necessary to acquire proper herbicide labeling, and to define the best management practices.

Germplasm

The original accessions from Africa are curated by the U.S. Department of Agriculture, Agricultural Research Service, Plant Introduction Station, Iowa State University, Ames, IA 50011, Mary Brothers, Curator.

Small research quantities of hybrid germplasm are available from Dr. David Dierig, USDA-ARS, U.S. Water Conservation Laboratory, 4331 E. Broadway Road, Phoenix, AZ 85040.

Key References

Selected Experts

Terry A. Coffelt, David A. Dierig, Francis S. Nakayama, USDA-ARS, U.S. Water Conservation Laboratory, 4331 E. Broadway Road, Phoenix, AZ 85041
Tel: 602 379-4356; Fax 602 379-4355; E-mail ddierig@uswcl.ars.ag.gov

Dennis T. Ray, The University of Arizona, Plants Sciences Department, 415D Forbes Building, Tucson, AZ 85021
Tel: 520 621-7612; Fax 520 621-7186: E-mail dtray@ccit.arizona.edu

Michael Foster, Texas A&M, Texas Agricultural Experiment Station, Firestone Site, West I-10, Ft. Stockton, Texas 79735
Tel: 915 336-7696; Fax: 915 336-7697

Richard Roseburg, Oregon State University, Southern Oregon Experiment Station, 569 Hanley Road, Medford, Oregon 97502
Tel: 503 772-5165; Fax: 503 772-5110

[Contributor: David A. Dierig, USDA, ARS, U.S. Water Conservation Laboratory]

Copyright © 1997. All Rights Reserved. Quotation from this document should cite and acknowledge the contributor.


Last update Tuesday, February 24, 1998 by aw