Waterthyme: Why This Aquatic Plant Should Stay Out of Your Garden
If you’re researching waterthyme (Hydrilla verticillata) for your garden or water feature, I need to stop you right there. While this submerged aquatic plant might seem appealing for ponds or water gardens, it’s actually one of the most problematic invasive species in North America. Let me explain why you’ll want to steer clear of this underwater troublemaker.
What is Waterthyme?
Waterthyme is a perennial aquatic forb – essentially an underwater plant that lacks significant woody tissue but packs a serious invasive punch. Originally from Asia, Africa, and Australia, this non-native species has established itself as an unwelcome guest across much of the United States, where it reproduces spontaneously and persists without any human help.
Where You’ll Find It (Unfortunately)
This aquatic invader has spread to an impressive 26 states, including Alabama, Arizona, Arkansas, California, Connecticut, Delaware, District of Columbia, Florida, Georgia, Indiana, Iowa, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Mississippi, New Jersey, New York, North Carolina, Pennsylvania, South Carolina, Tennessee, Texas, Virginia, and Washington. That’s a lot of territory for one troublesome plant!
Why Waterthyme is Bad News for Your Garden and Beyond
Here’s where things get serious. Waterthyme isn’t just invasive – it’s been classified with various levels of invasive and prohibited status across multiple states:
- Alabama: Category 1 invasive
- Connecticut: Invasive and prohibited
- Delaware: Invasive
- Michigan: Watch list and prohibited
- Minnesota: Prohibited
- Missouri: Invasive
- North Carolina: Invasive
- Wisconsin: Prohibited
To make matters worse, it’s also classified as a noxious weed at the federal level. When a plant earns this many red flags, you know it’s trouble.
The Wetland Menace
Waterthyme is what we call an obligate wetland species, meaning it almost always occurs in wetlands across every region of the United States. This specialization might sound harmless, but it actually makes the plant incredibly effective at colonizing and dominating aquatic habitats, choking out native species that wildlife depends on.
Why You Should Never Plant Waterthyme
I cannot stress this enough: do not plant waterthyme in your garden, pond, or any water feature. Here’s why:
- It forms dense underwater mats that crowd out native aquatic plants
- It disrupts entire aquatic ecosystems
- Once established, it’s extremely difficult and expensive to remove
- It can spread to natural waterways, causing environmental damage
- Planting it may be illegal in your state
Better Alternatives for Your Water Garden
Instead of waterthyme, consider these native aquatic alternatives that will support local wildlife without causing ecological havoc:
- Wild celery (Vallisneria americana)
- Coontail (Ceratophyllum demersum)
- Various native pondweeds (Potamogeton species)
- Water milfoil native species (depending on your region)
What to Do If You Find Waterthyme
If you suspect you have waterthyme in your pond or local waterway, contact your state’s invasive species program or extension office immediately. Early detection and rapid response are crucial for controlling this aggressive invader.
The Bottom Line
While waterthyme might seem like just another aquatic plant, its invasive nature and legal status make it a definite no-go for any responsible gardener. Stick with native alternatives that will beautify your water features while supporting local ecosystems. Your local wildlife (and your wallet) will thank you for avoiding this aquatic troublemaker.
Remember: the best garden is one that works in harmony with nature, not against it. Choose native plants, and leave the invasive species like waterthyme where they belong – far away from your garden.
