Nymphoides peltata is commonly known as yellow floating heart, fringed water lily, or entire marshwort. Notorious for being an aggressive weed, this infamous perennial belongs to the Menyathaceae or Buckbean family of wetland and aquatic plants. Along with its waterlily-resembling cousins, yellow floating heart is one of 50 species classified under the Nymphoides genus. It is set apart from its tropical cousins, however, as it is the sole Nymphoides species that can thrive under temperate conditions. Its native range extends from the Mediterranean to Eurasia, though it is now spread widely across Europe and North America.
This aquatic plant is typically bottom-rooted and has bright green foliage which floats on the water’s surface. It has earned its common name from its circular or heart-shaped leaves that spread to about 15 cm (5.9 inches) in diameter at maturity. With slightly scalloped margins, these leaves tend to have purplish undersides and are borne by long submerged stalks. Attached to a network of rhizomes underwater, the stalks also give rise to flower-bearing peduncles that stand a few inches above water.
The vivid yellow flowers, characterized by five distinctly fringed petals, are fleeting beauties that only last a day! When pollinated by bees or butterflies, these short-lived blooms develop into tiny capsules containing winged seeds.
Facts, Benefits & Uses of Yellow Floating Heart
Yellow floating heart was originally brought to the US as an ornamental pond plant. It has unfortunately earned ill-repute as a troublesome weed due to its extremely efficient forms of self-propagation. Its seeds have several adaptations, making everything that comes into contact with them a potential vector. Their winged margins allow them to float on the water’s surface. Moreover, they are covered in fine hairs that can cling to waterfowl, boating gear, and just about anything with which they come into contact.
In nature, N. peltata can be found in slow-moving bodies of water and may even thrive in swamps, canals, and waterways. Though it is associated with higher pond biodiversity, it must be cultivated with caution. Colonies usually form dense floating mats that can threaten the underlying aquatic ecosystem by shading out native plants. This can lead to reduced oxygen levels and the prevention of water flow. The resulting stagnant water conditions, in turn, may become breeding grounds for mosquitoes and other pests and may force resident wildlife to seek refuge elsewhere.
Yellow Floating Heart Growth, Hardiness & Climate
Hardy to USDA zones 5 – 10, N. peltata grows best in loamy soil and submerged in calm water. It thrives best under mesothermal to continental climate conditions with average temperatures above 10˚C (50˚F). As this species requires trace amounts of calcium for the production of its floating leaves, it prefers neutral to alkaline soil. Given proper growth requirements, it may reach a spread of 2.5 meters (8 feet) under full sun exposure. Aside from seed production, it can reproduce by vegetative means via its rhizomes, stolons, and leaves with intact stems.
Yellow floating heart is suited for cultivation in ponds or water gardens, as long as its growth can be restricted to your area. Bear in mind that under intense rainfall conditions, flooding of ponds can inadvertently spread fragments and seeds to the surrounding waterways. If it comes into contact with poorly-drained rich soil, it will spread more vigorously and may wreak havoc in natural systems.
How to Plant Yellow Floating Heart
This species can be grown via seeds, but is more easily propagated via fragments. Obtain runners during the summer and pot these in rich loamy soil. As this species can spread via rhizomes, it is advisable to restrict its growth to within pots. Submerge these pots in shallow water until roots are established. Once the crown is stable, pots can be moved deeper into your pond, up to a depth of 60 cm (2 feet).
If you intend to grow this plant via seeds, you may need to first create a greenhouse set-up. Sow seeds into pots that are submerged in at least 25 mm (1 inch) of water. Once the first true leaves appear, seedlings may be transferred into individual pots that are likewise kept submerged. It can take up to two years for individual seedlings to reach maturity. Once individual plants have developed root systems, you may transfer your pots into a shallow section of the pond or water garden. This should be done in late spring.
How to Care For Yellow Floating Heart
Yellow floating heart is a low-maintenance plant that will rarely require special attention. Simply make sure to keep the plant submerged in neutral to alkaline water, as it will not thrive in acidic conditions. Regularly check your pond water’s pH levels to ensure that it does not drop. Situate this plant in an area that receives ample sunlight and routinely check its leaves for typical waterlily pests, such as beetles, aphids, false leaf-mining midges, and moths. Remove dead or yellowing leaves from the water’s surface, as these will attract disease and unnecessarily block out light.
Note that this plant has weed potential and may have to be cut back or restricted with barrier materials to prevent pond invasion. Hand-pulling and mechanical removal may also be performed to control its growth.
How to Winter Yellow Floating Heart
Nymphoides peltata will not require special overwintering conditions as it naturally grows dormant during the winter. Its leaves and stems die back, and the plant remains intact as tuberous rhizomes. As long as these are submerged in a few feet of water, they will survive through the winter. If juveniles are being grown along the margins of your pond, you may consider transferring these into a warm area of your greenhouse. After the final frosts, expect shoots to reappear and grow towards the water’s surface once more.
Is Yellow Floating Heart Invasive or Toxic?
Considering its potential for both sexual and vegetative reproduction, yellow floating heart is capable of colonizing considerably large bodies of water, provided it has access to rich soil. It is considered an invasive species in several regions of the US (particularly the Great Lakes), and is even on the prohibited plant lists of several states, e.g. Michigan, Washington, South Carolina, Maine, etc. Its invasiveness or weed potential has also been noted in Sweden, New Zealand, and Ireland.
Fortunately non-toxic, this formidable plant has several pathway vectors and is a challenge to eradicate. It has impacted some areas enough to cause economic and social consequences, as the thick mats of vegetation can be costly to remove and serve as an impediment to tourist activities. If you are located in an affected area but would like to grow a similar plant, consider growing other non-invasive Nymphoides species that are native to your area.
Where to Buy Yellow Floating Heart & Seeds? (UK & US)
This species can be purchased from plant nurseries and aquascaping shops across its native range. It may also be purchased via online plant portals, but do bear in mind that there may be restrictions. If located in the US, you will need to check your state’s prohibited plant list prior to purchasing this species. Some areas have listed Nymphoides peltata in their quarantine list, making it illegal to trade, buy, sell, and distribute this species within their jurisdictions.
