Yellow floating heart (Nymphoides peltata)

Synonyms: Limnanthemum peltatum, Villarsia nymphoides, Nymphoides nymphaeoides

Common Names: fringed water lily, floating heart, entire marshwort

Description:

Yellow floating heart (Nymphoides peltata) is an invasive aquatic plant from Eurasia that was brought to North America as an ornamental for water gardens and ponds [2]. It has escaped into lakes, ponds, and slow streams, where it forms dense floating mats of small lily-like leaves topped with bright yellow flowers [2][3]. MISIN tracks it because those mats shade out native water plants, lower oxygen in the water, and make boating, fishing, and swimming difficult [2][3].

Habit:

Yellow floating heart is a rooted water plant that sends up long stalks from underwater stems, with leaves that float flat on the surface like small water-lily pads [3]. The leaves are heart-shaped to nearly round, 2 to 6 inches across, shiny green with slightly wavy edges, and often have reddish-purple blotches [3]. From June into October it produces bright yellow flowers that stand just above the water, each with five petals that have distinctly fringed (frilly) edges [3].

It is easiest to spot in summer, when the yellow fringed flowers are open above a carpet of floating leaves [3]. The combination of a small heart-shaped floating leaf and a yellow fringed flower is the giveaway ? native floating-leaf plants this size have white flowers, not yellow fringed ones [3].

At-a-glance cues:

1. Heart-shaped to round floating leaves, 2?6 inches across, with wavy edges and often reddish-purple blotches [3]
2. Bright yellow flowers held above the water, each with five fringed (frilly-edged) petals [3]
3. Flowers from June through October, singly or in small clusters [3]
4. Dense floating mats on still or slow-moving water [2][3]

Leaves:

1. Float flat on the water surface on long stalks rising from underwater stems [3]
2. Heart-shaped to nearly round, 2?6 inches (5?15 cm) across [3]
3. Margins smooth but slightly wavy or rippled [3]
4. Shiny green, often with reddish-purple blotches, resembling small water-lily pads [3]

Stems:

1. Soft, non-woody underwater stems and long leaf stalks (no woody parts) [3]
2. Roots in the bottom sediment and spreads along the bottom by underground stems (rhizomes) and runners (stolons) [2][3]
3. Broken stem, leaf, and node fragments can root and grow into new plants [2]

Flowers:

1. Bright yellow, about an inch or more across, held just above the water surface [3]
2. Five petals, each with distinctly fringed (frilly) edges [3]
3. Borne singly or in small clusters of up to five [3]
4. Bloom from June through October; each flower has both male and female parts [3]

Fruit and seeds:

1. Fruit is a capsule about an inch long, holding numerous flat, oval seeds [3]
2. Seeds have hairy or fringed edges that let them float on the water [2][3]
3. Ripe capsules split open and release the floating seeds, which drift and can stick to animals [2]
4. The plant also spreads heavily by rhizomes, runners, and broken fragments [2]

Habitat:

Yellow floating heart grows in still or slow-moving water ? ponds, lakes, swamps, channels, and slow streams [3]. It roots in the bottom and can grow in water from about 1.5 to 13 feet (0.5?4 m) deep, and it tolerates low-oxygen conditions [3].

The plant is native to Eurasia, from eastern Asia to Europe and the Mediterranean [1][2]. It was introduced to North America as an ornamental pond plant in the late 1800s and has since spread to many states across the country and into Canada [2].

Reproduction:

Yellow floating heart reaches new water in several ways, and people are a big part of it. It is sold and shared as a water-garden plant, and it escapes or is dumped into natural waters [2]. Once present, broken pieces ? a stem, a leaf with its node, or a bit of rhizome ? drift away and root into new plants, and these fragments hitch rides on boats, trailers, and fishing gear to other lakes [2]. Its seeds also float on the water and can cling to animals, spreading it downstream and around a lake [2].

The plant is a perennial that comes back year after year from its underwater stems, and it spreads fast by rhizomes and runners as well as by seed [2][3]. Because even small fragments can start new plants, the key to control is removing every piece and cleaning gear before moving between waters; remove plants before the seed capsules form during the June?October bloom to limit floating seed [2][3].

Impact and Damage:

Yellow floating heart is not known to harm people or pets directly, but it can ruin the use and health of a pond or lake. It grows into dense floating mats that cover the surface, blocking light to the water below and crowding out native water plants [2][3]. Those mats make it hard to boat, fish, or swim, and the still, shaded water beneath them can become stagnant [2][3].

For natural areas, the mats lower the oxygen in the water below, which can stress fish and other aquatic life and push wildlife to move elsewhere [2]. The shaded, low-oxygen water can also create good mosquito breeding habitat [2]. Once established, a single patch can expand quickly into a near-solid cover over a calm waterbody [2][3].

Similar species:

Several floating-leaf plants look similar, but the yellow, fringed flower of yellow floating heart sets it apart from native plants of the same size.

Native floating hearts (Nymphoides species, such as little floating heart) have similar small heart-shaped floating leaves, but their flowers are white, not yellow [3]. Fragrant water lily (Nymphaea odorata) has much larger round floating leaves with a single deep notch and large, many-petaled white-to-pink flowers, unlike the small leaves and fringed yellow flowers of yellow floating heart [3]. Spatterdock (yellow pond-lily, Nuphar species) does have yellow flowers, but they are large and cup- or ball-shaped rather than flat and fringed, and its leaves are much bigger [3]. Watershield (Brasenia schreberi) has small oval floating leaves attached at the center with no notch, dull reddish flowers, and a jelly-like coating on its undersides and stems [3].

Monitoring and rapid response:

Signs to watch for:

1. Patches of small, heart-shaped floating leaves with wavy edges on still or slow water [3]
2. Bright yellow, fringed flowers held above the surface from June through October [3]
3. Dense floating mats spreading across a pond, lake, or slow stream [2][3]

What you can do:

1. For small patches, hand-pull or rake out the plants, working to lift the rooted stems and rhizomes, not just the leaves [2].
2. Work carefully: every fragment ? a stem piece, a leaf with its node, or a bit of rhizome ? can grow into a new plant, so collect every piece [2].
3. Remove all plant material from the water and dispose of it on land away from the shoreline; do not compost it near water [2].
4. Remove plants before the seed capsules form during the summer bloom to limit floating seed [3].
5. Clean, drain, and dry boats, trailers, and gear before moving between waters so you do not carry fragments to a new lake [2].
6. Check first: removing aquatic plants from lakes and ponds is often regulated, so contact your state aquatic or environmental agency before treating or clearing plants in shared or public water.
7. Natural area crews should target small, new infestations and outlier patches first, use repeated coordinated removal with careful fragment control, and monitor downstream where seeds and pieces drift [2].

When to call a professional:

1. Established mats, large or flowing waterbodies, or any site where fragments could spread downstream.
2. Sites where hand removal cannot keep up with regrowth.
3. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. USDA NRCS Plants Database. Nymphoides peltata (S.G.Gmel.) Kuntze. plants.usda.gov
2. U.S. Geological Survey, Nonindigenous Aquatic Species Database. Nymphoides peltata ? Species Profile. nas.er.usgs.gov
3. Michigan Department of Natural Resources. Invasive Species: Yellow Floating Heart. michigan.gov/invasives
4. Minnesota Department of Natural Resources. Yellow Floating Heart (Nymphoides peltata). dnr.state.mn.us
5. Invasive Species Centre. Yellow Floating Heart. invasivespeciescentre.ca

---