Pennycress, or Thlaspi arvense, has long been viewed as a common agricultural weed. The plant is undergoing a significant shift in perception, moving from a persistent nuisance to a resource with considerable potential as researchers explore its beneficial properties. This transformation highlights a trend in agriculture where plants once considered undesirable are cultivated for new and valuable applications.
What is Pennycress?
Field pennycress is a winter annual in the Brassicaceae family, which includes mustard and canola. It typically grows up to 24 inches tall and features small, white flowers. The plant’s most defining characteristic is its seed pods, which are flat and round with a distinct notch at the top, resembling small coins and giving the plant its name. Each pod contains several small, dark seeds.
Historically, pennycress has been a pervasive weed in agricultural fields across North America and Eurasia. Its resilience and ability to produce up to 15,000 seeds per plant allowed it to spread widely. The plant also earned the nickname “stinkweed” because of the pungent, garlic-like odor it releases when its leaves and stems are crushed.
Pennycress as an Agricultural Cover Crop
As a cover crop, pennycress offers agricultural and environmental benefits during the fallow period between cash crops. Planted in the fall after the primary harvest, it establishes a dense root system that holds soil in place throughout the winter and early spring. This living cover is effective at preventing soil erosion from wind and water, protecting valuable topsoil.
The plant’s root system also plays an important role in nutrient management. Pennycress scavenges for residual nutrients in the soil, most notably nitrogen. By absorbing this excess nitrogen, the crop prevents it from leaching into groundwater or running off into nearby waterways, which helps protect water quality. This process also improves soil structure and retains nutrients for subsequent crops like corn and soybeans.
Industrial Products from Pennycress
The most significant modern applications for pennycress stem from products derived from its seeds. After harvest, the seeds, which contain a high oil content of 30-36%, are pressed to extract this oil. This oil is a primary feedstock for renewable fuels and can be refined into biodiesel and sustainable aviation fuel (SAF), a lower-emission alternative to conventional jet fuel.
Once the oil is extracted, a high-protein seed meal is left behind. This co-product shows promise as an ingredient for animal feed because it contains a favorable amino acid profile. However, wild-type pennycress meal contains high levels of glucosinolates, compounds that can be harmful to livestock. The meal must undergo processing to reduce these compounds and create a safe feed supplement.
Cultivation in Modern Farming
Pennycress is being integrated into modern farming systems, particularly the corn-soybean rotation common in the U.S. Midwest. Its life cycle as a winter annual allows it to be planted in the fall after corn is harvested and then harvested in the spring before soybeans are planted. This timing allows farmers to introduce a “third crop” into their rotation, generating income from land that would otherwise be unproductive.
To enhance its viability, research and domestication efforts are underway. Scientists use breeding and gene-editing to develop improved varieties, sometimes marketed as CoverCress. These efforts focus on creating pennycress lines with desirable traits like larger seeds, higher oil content, reduced glucosinolate levels, and earlier maturation. These improvements are aimed at making pennycress a more profitable option for farmers.