The Tell-Tale Crested Floating Heart: Rid your pond of this invasive plant

Observations from a graduate student — by Corrina Vuillequez

A dense layer of CFH on pond surface, unable to see water beneath. — CFH leaves can cover the entire surface of a pond, blocking sunlight from the plants below.

At first glance, this species looks like a friendly cousin to the lily pad. With heart-shaped floating leaves and abundant white flowers, crested floating heart (Nymphoides cristata) seems like an appealing ornamental, and is often marketed as “water snowflake”. However, what starts as a cute new addition to your pond can quickly become a major headache.

Crested floating heart (or “CFH” for short) is classified as a Category 1 invasive species by the Florida Invasive Species Council. It is also listed on the Florida Noxious Weed List (Gettys et al. 2017). This means that CFH can alter the ecology of water bodies by displacing native plants. It is illegal to introduce, multiply, possess, move, or release CFH without a state permit in Florida. CFH poses a high risk to areas outside of Florida as well: The USDA estimates that 11% of the U.S. is suitable habitat for CFH, specifically in the southeast (USDA APHIS 2012).

Invasive Qualities

So, what makes this unassuming looking plant so invasive? CFH has a unique biology which makes it especially prolific and resilient. While it yields many flowers, they don’t produce viable seeds in the United States. Instead, CFH reproduces asexually through structures called ramets, which are propagules typically produced under the leaves of the plant. These ramets are clones with the same DNA as the mother plant. They will eventually separate from the mother from wind or wave action. It’s similar to how a succulent reproduces – any little piece falling off is able to root into a whole new plant. A single mother plant can produce up to 500 ramets in 6 months, 40% of which are likely to detach and sprout (Markovich et al. 2021).

Below the surface of the sediment, another beast looms – mature CFH plants produce massive root systems. Little documentation exists on CFH root biology, but I have observed that CFH root crowns become large and starchy, almost like a giant aquatic carrot. It is likely that these aid in energy storage for colder months and contribute to the species re-growing after herbicide treatments.

three images of the CFH ramets — Left: A ramet attached to a mother plant.
Middle: A typical ramet found detached from the mother plant, at the water’s surface.
Right: A ramet found dormant on the hydrosoil.

CFH carrot-like root being held in hand. — A mature CFH root crown bisected with a knife.

Impacts

Once introduced, CFH is extremely hard to get rid of. Its floating leaves can grow to cover the entire surface of a pond, blocking sunlight from reaching the native aquatic plants below. This can cause the native plants to die off, therefore reducing dissolves oxygen levels in the water and possibly leading to fish kills. On a larger scale, CFH can impede recreation, flood control, and navigation in lakes and canals (Willey et al. 2014). Achieving long-term control relies on herbicides and continues to be a difficult process, which I am seeking to improve through my work at the University of Florida.

How to Properly Rid Your Pond of CFH

If you think you have crested floating heart in your backyard pond or aquarium, take a moment to properly identify it, as there are several lookalikes in the United States. The tell-tale sign of CFH are the 3D crests in the center of each flower petal. If you do have the species, make sure to dispose of it properly. Try to collect as much of the plant material as possible, including the roots, before disposing of it in a trash bag. If the plants are in a pond, you’ll likely need waders and a shovel to fully get the roots out. At the UF/IFAS Center for Aquatic and Invasive Plants, we use drying ovens to fully destroy invasive plants before disposal. Fully dried out plants can be disposed of outside, in a trash can, or used as compost.

Native Alternatives

If you like the look of the species for your pond or aquarium, there are two native lookalikes which make great alternatives. Banana lily, also known as big floating heart, (Nymphoides aquatica), and little floating heart (Nymphoides cordata). These native floating aquatic plant species have similar-looking leaves and pretty white flowers, without the unwanted invasive characteristics (Markovich et al. 2021). We all have a part to play in keeping the spread of CFH at bay. At the UF/IFAS Center for Aquatic and Invasive Plants, we are working with vegetation managers to develop improved management protocols for controlling CFH. As a homeowner or aquarium hobbyist, make sure to shop responsibly for aquatic ornamentals, and dispose of invasive plants properly.

References

Gettys LA, Della Torre III CJ, Thayer KM, Markovich IJ. 2017. Asexual reproduction and ramet sprouting of crested floating heart (Nymphoides cristata). J. Aquat. Plant Manage 55:83–88.

Markovich IJ, Sigmon JW, Gettys LA. 2021. Chapter 2.9: Floatinghearts, pp. 59-64. In: Biology and Control of Aquatic Plants: A Best Management Practices Handbook. Fourth Edition. Aquatic Ecosystem Restoration Foundation, Marietta GA. 224 pp.

USDA APHIS. 2012. Weed risk assessment for Nymphoides cristata (Roxb.) Kuntze (Menyanthaceae) – Crested floating heart. USDA Noxious Weeds Program Risk Assessments. 16 pp.

Willey LN, Netherland MD, Haller WT, Langeland KA. 2014. Evaluation of herbicide activity against crested floating heart. J. Aquat. Plant Manage 52:47-56.

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