Twoleaf Watermilfoil: A Native Plant That’s Better Left Wild
When it comes to native aquatic plants, twoleaf watermilfoil (Myriophyllum heterophyllum) presents gardeners with a bit of a puzzle. While this perennial forb is indeed native to much of North America, it’s earned a reputation as a plant that’s better appreciated in its natural habitat than invited into your backyard water feature.
What Is Twoleaf Watermilfoil?
Twoleaf watermilfoil gets its common name from its unique characteristic of having two very different types of leaves. The submerged portions display delicate, feathery foliage that looks almost like underwater Christmas trees, while any emergent parts produce broader, more typical-looking leaves. This herbaceous perennial is classified as an obligate wetland plant, meaning it almost always occurs in wetland environments across all regions of North America.
Where Does It Grow?
This native species has an impressive geographic range, naturally occurring across a vast swath of North America. You’ll find it growing wild from British Columbia to New Brunswick in Canada, and throughout most of the continental United States, including Alabama, Arkansas, Connecticut, Delaware, Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Virginia, West Virginia, and Wisconsin.
The Problem with Planting Twoleaf Watermilfoil
Here’s where things get tricky for gardeners. Despite being native, twoleaf watermilfoil has earned invasive status in some areas due to its aggressive spreading habits. Connecticut lists it as Invasive, Prohibited, while New Mexico has classified it as Prohibited. This means it’s actually illegal to plant or propagate this species in these states.
Even in areas where it’s not officially banned, this plant’s vigorous growth can quickly overwhelm small water features and crowd out other desirable aquatic plants. What starts as a small addition to your pond can rapidly become a management headache.
Conservation Considerations
Interestingly, while some states are fighting to control twoleaf watermilfoil, others are working to protect it. In New Jersey, it holds a rarity status of Highlands Listed, S3, indicating it’s considered vulnerable in that region. This highlights how the same species can behave very differently depending on local conditions and ecosystems.
Better Alternatives for Your Water Garden
If you’re looking to add native aquatic plants to your pond or water feature, consider these well-behaved alternatives:
- Wild celery (Vallisneria americana) – provides similar underwater structure without aggressive spreading
- Pickerelweed (Pontederia cordata) – offers beautiful blue flower spikes and attracts pollinators
- Arrowhead (Sagittaria latifolia) – distinctive arrow-shaped leaves and white flowers
- Native water lilies – provide surface coverage and stunning blooms
Growing Conditions (For Educational Purposes)
Should you encounter twoleaf watermilfoil in the wild, you’ll typically find it thriving in:
- Standing or slow-moving freshwater
- Full sun to partial shade conditions
- USDA hardiness zones 4-9
- Various water depths, from shallow margins to deeper areas
The Bottom Line
While twoleaf watermilfoil is undoubtedly a fascinating native plant with an important ecological role in natural wetlands, it’s simply not suitable for most residential water gardens. Its aggressive nature and legal restrictions in some areas make it a plant that’s best left to thrive in its natural habitats.
Instead, focus on selecting native aquatic plants that will enhance your water feature without taking it over. Your local native plant society or extension office can help you identify the best options for your specific region and growing conditions. Remember, being native doesn’t always mean being garden-appropriate!
