Field Pennycress: Understanding This Widespread Non-Native Annual
If you’ve ever noticed small white flowers clustered atop slender stems in early spring, followed by distinctive heart-shaped seed pods, you’ve likely encountered field pennycress (Thlaspi arvense). This hardy annual forb has made itself quite at home across North America, though it originally hails from Europe and western Asia.
What is Field Pennycress?
Field pennycress is a non-woody annual plant that belongs to the mustard family. As a forb, it lacks significant woody tissue and completes its entire life cycle within a single growing season. The plant is characterized by its small, four-petaled white flowers that bloom in dense clusters, followed by its most distinctive feature – flattened, heart-shaped seed pods that give it a unique appearance in the landscape.
Where You’ll Find It
This adaptable plant has established itself throughout virtually all of North America, from Alaska to Florida and from coast to coast. It grows in all U.S. states, Canadian provinces and territories, and even extends into Greenland. Field pennycress thrives in disturbed soils, agricultural areas, roadsides, and waste places.
Growing Characteristics and Habitat
Field pennycress is remarkably adaptable and hardy, which explains its widespread distribution. Here are its key growing traits:
- Soil preferences: Thrives in poor, disturbed soils and tolerates a wide range of soil conditions
- Water needs: Classified as obligate upland in most regions, meaning it rarely occurs in wetlands
- Sunlight: Grows best in full sun to partial shade
- Climate: Cool-weather annual that can establish in USDA zones 2-10
- Growth habit: Forms rosettes in fall, then sends up flowering stems in spring
Should You Grow Field Pennycress?
Here’s where things get interesting. While field pennycress isn’t typically sold in garden centers or featured in landscape designs, it does have some characteristics that might appeal to certain gardeners:
Potential Benefits:
- Early spring blooms provide nectar for small pollinators when few other flowers are available
- Extremely low-maintenance once established
- Interesting seed pods add texture to wild or naturalized areas
- Can help stabilize disturbed soil
Considerations:
- As a non-native species, it doesn’t provide the same ecological benefits as native plants
- Can self-seed aggressively and may spread beyond intended areas
- Often considered a weed in agricultural settings
- Short bloom period and somewhat unremarkable appearance
Native Alternatives to Consider
If you’re drawn to field pennycress for its early spring flowers and low-maintenance nature, consider these native alternatives that provide similar benefits with greater ecological value:
- Wild ginger (Asarum canadense): Low-growing native groundcover
- Spring beauty (Claytonia virginica): Early spring wildflower
- Toothworts (Cardamine species): Native mustard family members with similar flowers
- Wild columbine (Aquilegia canadensis): Native spring bloomer
If You Choose to Grow It
Should you decide to incorporate field pennycress into a wild garden or naturalized area, here’s what you need to know:
- Planting: Seeds can be direct-sown in fall or early spring
- Care: Requires virtually no maintenance once established
- Management: Monitor for excessive self-seeding and remove unwanted plants before they set seed
- Best uses: Disturbed areas, wildlife gardens, or areas where you want temporary ground cover
The Bottom Line
Field pennycress is one of those plants that gardeners are more likely to encounter than intentionally plant. While it’s not necessarily harmful to grow, its non-native status means it won’t provide the same benefits to local wildlife and ecosystems as native species would. If you appreciate its early flowers and hardy nature, consider exploring native alternatives that offer similar characteristics with greater ecological value.
Whether you embrace it as a quirky addition to a wild garden or remove it in favor of native species, understanding field pennycress helps you make informed decisions about the plants in your landscape.
