Field Pennycress (Thlaspi arvense)

Field pennycress has many distinct uses. Although it is not normally suitable for human consumption due to its bitter taste, the plant is used as fodder for livestock. In addition, the oil from field pennycress has been found to be a highly suitable renewable source for biodiesel and jet fuel.

I. Appearance and Characteristics 

Thlaspi arvense, known by the common name field pennycress, is a flowering plant in the cabbage family Brassicaceae. It is native to Eurasia, and is a common weed throughout much of North America and its home.

Thlaspi arvense is a foetid, hairless annual plant, growing up to 60 cm (24 in) tall, with upright branches. The stem leaves are arrow-shaped, narrow and toothed. It blooms between May and July, with racemes or spikes of small white flowers that have 4 sepals and 4 longer petals. Later it has round, flat, winged pods with a deep apical notch, measuring 1 cm (0.39 in) across. They contain small brown-black seeds.

The common name ‘pennycress’ is derived from the shape of the seeds looking like an old English penny. Other English common names are: stinkweed, bastard cress, fanweed, field pennycress, frenchweed and mithridate mustard. Pennycress is an annual, overwintering herb with an unpleasant odor when its leaves are squeezed. It grows up to 40 to 80 cm depending on environmental conditions. White, lavender or pink flowers with four petals develop between five and eight seeds. Numbers of chromosomes is 2x. Pennycress, has flat and circular notched pods. Its seeds have a high oil content and the species has gained interest as a potential feedstock for biofuel production.

Pennycress is planted and germinates in the fall and overwinters as a small rosette. The central stem and upper side stems terminate in erect racemes of small white flowers. Flowers are self-pollinated and produce a penny sized, heart-shaped, flat seed pod with up to 14 seeds. Each dark brown seed is oval-shaped and slightly larger than a camelina seed (Camelina sativa). Pennycress grows as a winter annual across much of the Midwestern US and the world.

II. How to Grow and Care

Sunlight

Field pennycress thrives best in full sun conditions, receiving ample light throughout the day to promote healthy growth. Although field pennycress can tolerate partial sun, its growth may slow and health can be compromised if it doesn’t receive the preferred level of light intensity. With the ability to adapt to varying sunlight, field pennycress can still perform well when light conditions are not ideal, but for optimal health and vigour, planting it in open areas where direct light is abundant will yield the best results. It is recommended for outdoor cultivation rather than indoor cultivation as it needs the intensity of natural sunlight to flourish.

Watering

Field pennycress is a plant that thrives in areas with moderate rainfall, showing a relative balance in its water needs. Watering every week suffices to keep this plant healthy and vibrant. Being a deciduous plant, field pennycress sheds its leaves during dry periods to conserve water, indicating its inherent adaptation to fluctuating water availability.

Fertilizing

In order to increase yields several studies evaluated the effect of fertilization on pennycress. Generally cover crops like pennycress are used to take up the available nutrients to prevent them from leaching. Nitrate and sulphur fertilization had positive effects on the seed yield of pennycress, but also no fertilized treatments showed sufficient yields.

Propagation

Field pennycress is easily propagated by sowing seeds in the spring. This straightforward method requires no special skills or tools. Signs of successful propagation include germination and healthy seedling growth. Ensure proper soil preparation and moisture for best results.

Transplanting

The ideal time to transplant field pennycress would be between Seasons 1 and 2, when the environment is most conducive for growth. Placement is key, so choose a sunny location with good drainage. A gentle reminder – never overwater field pennycress after transplanting to prevent root rot.

III. Uses and Benefits 

• Oil

The first attempts to grow pennycress as an oil crop took place in 1994. However, since 2002 it is more and more considered as a potential oil crop rather than a “noxious weed”. High erucic acid content (>300g per kg of its total seed oil DM) makes the oil from landraces unsuitable for food purposes. Pennycress landraces also contain Glucosinolates, which make the usage as food undesirable. Recently pennycress oil has attracted great interest as raw material for jet fuel and Biodiesel production. Oils with high erucic acid are especially suitable for jet fuel production. Oil characteristics are highly influenced by specific environmental conditions such as precipitation.

• Feed

Due to the high erucic acid content the seeds are unsuitable for human consumption. Instead, the biomass can be used as feed for livestock. Its fast growth under cold conditions favors the usage as fodder as a second crop. Its low biomass production makes it undesirable to concentrate on pennycress cultivation for fodder production.

• Food

The field pennycress has a bitter taste; it is usually parboiled to remove the bitter taste. This is mostly used in salads, sometimes in sandwich spreads. It is said to have a distinctive flavor.

• Use as a source of biodiesel

Pennycress is being developed as an oilseed crop for production of renewable fuels. The species can be planted in the fall, will germinate and form a vegetative mass which can overwinter. In the spring, the oil-rich seed can be harvested and used as a biodiesel feedstock.

IV. Harvesting and Storage

• Harvesting

Pennycress can be harvested with common machinery used for grain/corn and soybean production. This makes it favorable for integration in many crop rotations. As pennycress is grown over the winter period the combines for harvesting are available in spring time as the harvest of all other crops happens at a different time of the year. The seed yield ranges for pennycress grown as a production crop currently range from 1000 kg/ha to 1500 kg/ha

• Integration in soy maize crop rotations

In the mid east of the US a common crop rotation is Soybean and Maize. After harvest the fields are kept as fallows. Pennycress appears to be especially well suited for oil production when cultivated before soybean. As a cover crop grown over the winter period with harvest taking place in spring, it can effectively reduce soil erosion, prevent nutrient leaching, improve soil structure and increase biodiversity. The required machinery for cultivation is already available in the region, as it is the same used for maize and soybean production. In the Mid-western United States, its use as a rotation crop with soybean and maize maintains the pathogen Soybean Cyst Nematode (Heterodera glycines), though less effectively than other legumes