Pennycress: A Hardy Annual That Divides Gardeners
If you’ve ever wondered about that small, white-flowered plant popping up in disturbed soil around your neighborhood, you might be looking at pennycress (Microthlaspi). This unassuming annual has a knack for appearing where you least expect it, and whether that’s a blessing or a nuisance depends entirely on your gardening perspective.
What Exactly is Pennycress?
Pennycress is an annual forb – essentially a non-woody flowering plant that completes its entire life cycle in one growing season. Don’t let its humble appearance fool you; this little survivor has made itself quite at home across much of North America, despite originally hailing from Europe and western Asia.
As a non-native species, pennycress has successfully established itself in the wild throughout much of Canada and the United States, reproducing without any human assistance. It’s what botanists call naturalized – not native, but not necessarily going anywhere either.
Where You’ll Find Pennycress
This adaptable little plant has spread across an impressive range, currently growing in Arkansas, Ontario, Quebec, District of Columbia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Missouri, New Jersey, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, Tennessee, Virginia, Washington, and West Virginia.
The Pennycress Look
Pennycress won’t win any beauty contests, but it has its own understated charm. The plant forms a low rosette of small leaves and sends up delicate stems topped with clusters of tiny white flowers. What really catches the eye are the distinctive heart-shaped seed pods that follow – these flat, coin-like pods are what give pennycress its common name.
Expect this annual to reach modest heights, typically staying close to the ground in its rosette form before sending up flowering stems.
Growing Conditions and Care
Here’s where pennycress really shines – it’s practically indestructible. This hardy annual thrives in USDA zones 3-9 and isn’t particularly fussy about its living conditions:
- Sunlight: Full sun to partial shade
- Soil: Well-draining soil, but tolerates poor conditions
- Water: Drought tolerant once established
- Maintenance: Minimal – this is a plant and forget species
The real appeal of pennycress lies in its ability to colonize disturbed soils and areas where other plants struggle. It’s particularly fond of roadsides, vacant lots, and anywhere the soil has been turned over.
Garden Role and Design Considerations
Pennycress works best in naturalized areas, cottage gardens, or spaces where you want a low-maintenance ground cover that can handle tough conditions. It’s excellent for filling in bare spots and can serve as a living mulch in informal garden settings.
However, keep in mind that this plant is a prolific self-seeder. Once established, you’re likely to see it returning year after year, and it may spread beyond where you originally planted it.
Wildlife and Pollinator Benefits
The small white flowers of pennycress provide an early source of nectar for small bees and other beneficial insects, particularly valuable because it blooms when many native plants are still dormant. While it’s not a powerhouse pollinator plant, every little bit helps support local insect populations.
Should You Plant Pennycress?
This is where things get interesting. Pennycress is remarkably easy to grow and can fill challenging spots in the landscape. However, as a non-native species with a tendency to self-seed enthusiastically, it’s worth considering whether there might be native alternatives that could serve your garden better.
Consider these native alternatives that offer similar benefits:
- Wild ginger for shaded groundcover
- Wild strawberry for sunny areas
- Native violets for early spring color
- Wintergreen for evergreen groundcover
If you do choose to grow pennycress, be prepared for its self-seeding nature and consider whether you’re comfortable with it potentially spreading beyond your intended planting area.
The Bottom Line
Pennycress is one of those plants that perfectly embodies the phrase one gardener’s weed is another’s wildflower. It’s incredibly easy to grow, requires virtually no care, and provides some wildlife benefits. Just be aware that once you invite it into your garden, it may decide to stay longer than originally planned – and bring friends.
