By Vikram Koundinya, Iowa State University and Ray Hansen, program director, AgMRC, Iowa State University, email@example.com.
Updated March 2012.
Field pennycress (Thlaspi arvense) is primarily an annual weed of winter small grains, nurseries and horticultural crops that is found throughout the United States. A member of the mustard family, it is known by common names like Frenchweed, fanweed or stinkweed in different areas of the country. Although established in every state except Hawaii, pennycress is abundant in the northern states, especially in the northwest, and more sparsely established in the southeast. It is found in waste places, open disturbed areas, roadsides, railroads, sometimes in grasslands, old fields, riparian areas and forest edges.
Young leaves are without hairs, round to oval in outline, with a distinct white midvein and wavy margin. Individual flowers are very small and occur in clusters at the ends of the 'bottle-brush' stems. Leaves initially have a wavy margin. Leaves along the flowering stem have toothed margins and pointed lobes that clasp the stem at the base of the leaf. The root system consists of a taproot. The stem is erect, ranging from 4 to 24 inches in height, branching in the upper portions and without hairs. Each seed pod is circular, approximately 1/2 inch in diameter, relatively flat and distinctly winged along the outer margins. Each pod divides in half and may contain as many as 16 seeds.
The oval, hairless leaves of the rosette, leaves with pointed lobes that clasp the flowering stem and bottle-brush appearance of the seedhead are the characteristics that help in the identification of field pennycress. This species is a prolific seeder (about 7,000 seeds per plant) and forms a long-lived (up to 20-30 years) seedbank, making it difficult to eradicate from an area once it becomes common.
Field pennycress has some potentially significant industrial applications. Its seeds contain about 26 percent oil, and this oil contains about 40 percent euric acid, a fatty acid. This fatty acid is similar to that of biodiesel resources, including animal fats and soybean and sunflower oils. Biodiesel from these sources can be used alone or mixed with petroleum-based diesel to lower the emission of hydrocarbons, carbon monoxide and other pollutants in engine exhaust. Crushed seed left over from biodiesel production, called meal, also has promise as an organic fertilizer and natural weed killer for low-acreage, high-value crops.
Another pennycress species found in the United States is called alpine pennycress (Thlaspi caerulescens). It is a small perennial plant having small rosettes of leaves that grow on unbranched stems. The plant has small, arrow-shaped leaves that end in tiny white flowers. In the United States, alpine pennycress is found in the Western states of Texas, Colorado, Wyoming and Montana. Unlike field pennycress, the pods of the alpine pennycress do not resemble pennies; they are more heart-shaped. However, the flowers are more distinctive, being white or lilac with violet anthers.
Alpine pennycress is known to absorb heavy metals. USDA and University of Maryland researchers found that this species of pennycress can remove cadmium and zinc metals from soil. The cost of the remediation method, called “phytoextraction,” was about $250 to $1,000 per acre per year. Thus, the method is cheaper than other methods of soil reclamation.
Acidifying soil helps plant remove cadmium, zinc metals, Ag Research Service (ARS), USDA, 2005 - Researchers found that increasing soil acidity can maximize the ability of alpine pennycress to remove cadmium and zinc metals from soil.
Field Pennycress: Thlaspi arvense, Weed Identification Guide, Virginia Tech.
Midwestern Weed May Inspire Newfound Respect, ARS, USDA, 2006 - This article discusses the economic potential of field pennycress. ARS scientists believe that field pennycress seed might be useful for making biofuel and a nature-based weed killer.
- The biology and non-chemical control of field pennycress (Thlaspi arvense L.), Henry Doubleday Research Association, UK, 2007 - Written by an organic organization, this article gives a botanical description of and control measures for field pennycress. The uses and harmful effects of field pennycress are also discussed.
- Making Pennycress Pay Off, Biodiesel magazine, 2008 - Illinois researchers believe they have developed the ability to transform a weed into a biodiesel feedstock.
- Biofumigant compounds released by field pennycress (Thlaspi arvense) seedmeal, ARS, USDA, 2005 - USDA research was conducted on defatted field pennycress seedmeal. This seedmeal appeared to offer potential as a biofumigant for high-value horticultural crops for both conventional and organic growers.
Plants, from pennycress to willow, have potential to cleanup polluted soils, researchers are finding; Chronicle Online; Cornell University; 2007.
- A taste for heavy metal, Nature, 2003 - A Purdue University study determined that pennycress was the most promising crop that could be used to reclaim heavy metal rich soils.
- Green Technology Research: Phytoremediation Case Study, University of Washington, 1990-1993 - This case study describes the phytoremediation carried out at the Pig's Eye Landfill in St Paul, Minnesota. Researchers planted pennycress and four other plants at the site, which was contaminated with waste from incinerated sewage sludge, to reduce the toxic levels of cadmium and zinc.
Written January 2008 and updated March 2012.