Whitetop: Why This Pretty Perennial Should Stay Out of Your Garden
If you’ve ever come across whitetop (Cardaria) in the wild, you might have been charmed by its delicate white flowers dancing in the breeze. But before you consider adding this perennial to your garden, there’s something important you need to know about this seemingly innocent plant.
What Exactly is Whitetop?
Whitetop is a perennial forb herb – basically a non-woody plant that comes back year after year. It’s part of the mustard family and produces clusters of small, four-petaled white flowers that can be quite attractive. The plant has gray-green leaves and can form dense patches that spread across the landscape.
The Not-So-Native Truth
Here’s where things get complicated: whitetop isn’t native to North America. This European and Asian transplant has made itself at home across a huge swath of the continent, from coast to coast. You can find it established in most U.S. states and several Canadian provinces, thriving in places where it frankly shouldn’t be.
The plant has spread extensively across North America, establishing populations in Alberta, British Columbia, Manitoba, New Brunswick, Nova Scotia, Ontario, Quebec, Saskatchewan, and numerous U.S. states including Arizona, California, Colorado, Connecticut, Delaware, District of Columbia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nebraska, Nevada, New Jersey, New Mexico, New York, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Dakota, Texas, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, and Wyoming.
Why Whitetop is a Garden No-Go
While whitetop might look pretty, it’s actually considered an invasive species in many areas. Here’s why you should think twice about planting it:
- It spreads aggressively through underground rhizomes
- Seeds disperse easily, establishing new colonies
- It outcompetes native plants for resources
- Once established, it’s incredibly difficult to remove
- It can take over entire areas, reducing biodiversity
Growing Conditions (If You Encounter It)
Whitetop is frustratingly adaptable, which is part of what makes it such a successful invader. It thrives in USDA hardiness zones 3-9 and tolerates a wide range of growing conditions:
- Various soil types, from clay to sandy
- Both moist and drought conditions
- Full sun to partial shade
- Disturbed areas, roadsides, and agricultural fields
Better Alternatives for Your Garden
Instead of planting whitetop, consider these native alternatives that offer similar aesthetic appeal without the ecological baggage:
- Wild bergamot (Monarda fistulosa) – aromatic with lavender flowers
- White prairie clover (Dalea candida) – elegant white flower spikes
- Yarrow (Achillea millefolium) – white flowers and feathery foliage
- Wild ginger (Asarum canadense) – excellent native ground cover
What to Do If You Have Whitetop
If you discover whitetop on your property, the best approach is removal. Small patches can be hand-pulled (get the entire root system), while larger infestations may require professional help. Never compost whitetop plants, as they can re-establish from root fragments.
The Bottom Line
While whitetop might seem like an easy-care perennial with pretty flowers, its invasive nature makes it a poor choice for responsible gardeners. By choosing native alternatives, you’ll create a more sustainable landscape that supports local wildlife and ecosystems. Your garden – and the environment – will thank you for making the more thoughtful choice.
