Nymphoides indica is a flowering perennial herb that is commonly known as water snowflake, floating heart, or robust marshwort. It is one of 70 species under the Menyanthaceae family, which includes an assortment of wetland plants that spread via creeping rhizomes. Those that are classified under the genus Nymphoides maintain a fully submersed aquatic habit and are popularly known for their resemblance to water lilies (Nymphaea). Due to their attractive features, they are often used as ornamental pond and aquarium plants.
Like many of its cousins, N. indica has a pantropical range that spans most of the equator. The simple heart-shaped leaves of this species grace the surface of many freshwater habitats. These expand to up to 8 inches (20 cm) across and are a lovely emerald green color under full sun.
In contrast, this plant’s flowers produce white petals that are especially notable for their frilly edges. These densely fringed petals, numbering 5 – 6 per flower, are borne on stalks that rise high above the floating foliage. The flowers extend to just an inch (2.5 cm) across and look remarkably like snowflakes on a warm summer day! When pollinated, these become capsule-like fruits containing a few spherical seeds.
Facts, Benefits & Uses of Water Snowflake
Water snowflake is normally found in lakes, ponds, bogs, and marshes in areas that experience warm or mild winters. It is a tender plant that can spread quite aggressively by multiple means. These include free-floating adventitious roots, plantlets produced along its leaves, and seeds that can withstand pond bottom conditions for up to 3 years. As a result, the weed potential of this species has been highlighted by several regions in the US. When properly controlled, however, Nymphoides indica is a charming marginal plant that can help keep your pond clean by filtering out nitrates.
This aquatic plant is sure to provide pond owners with fleeting summer joys as its frilly flowers last for just a day! Its vegetative parts can increase the structural richness of pond margins, thereby providing shelter and protection for spawners, juvenile fish, and visiting amphibians. Water snowflake is sometimes harvested from the wild as its parts are a great source of nutrition.
Water Snowflake Growth, Hardiness & Climate
Water snowflake is generally tolerant of many light and depth conditions, as long as its vegetation is not exposed to frosts. Although a few leaves develop floating roots, the majority of its shoots can grow to a full marginal depth and eventually become rooted in muddy sediment. Hardy to USDA zones 8 – 11, this species prefers to grow in water temperatures that range from 20 – 27˚C (68 – 81˚F) and thrives best in a slow-moving or mild current.
A single water snowflake plant can have a spread of up to 2 feet (60 cm) wide. When grown in colonies, the plant can provide ample shade to significantly reduce algal growth. Caution must be taken when cultivating populations, as these can spread quite vigorously. To prevent uncontrolled growth, plantlets and leaves with adventitious roots may have to be removed regularly. Keep in mind that seeds may also sink to your pond bottom (or spread to other waterways) and generate new plants over time.
How to Plant Water Snowflake
Water snowflake can be planted via seed or propagated using leaf plantlets, cuttings, and root divisions. The most straightforward means of cultivating this plant is done by using plantlets, which produce their own floating roots, or mature stalk cuttings, which eventually produce young white-colored roots. Once enough roots have formed, these can be planted in a pot with clay soil or left to grow on their own towards the substrate. The entire plant may become established even if just a third of its roots are buried in soil or gravel. The calmer the water, the more quickly roots are able to anchor themselves.
The leaves of this plant can be induced to produce roots if placed in a dish/basin set-up that is rich in iron or fertilizer. You may opt to cut off the section of the leaf that has produced ample roots. Plant this leaf section in submerged soil, preferably under 1 – 3 inches (2.5 – 7.6 cm) of water so that ample sunlight is still provided. This way, new baby plants should form. Adjust the water depth according to your desired growth habit.
If you are able to obtain bare-rooted water snowflake plants, plant these as soon as possible in pots or mesh baskets with fine soil or aquatic gravel. These can be placed directly into your pond, at a depth of 4 – 12 inches (10 – 30 cm), and gradually moved into deeper areas as the shoots increase in height.
How to Care For Water Snowflake
Water snowflake is generally easy to care for and is not susceptible to many pests and diseases. Do look out for snails as these can severely damage the leaves if left to feed on the plant. To ensure that your plant produces floating leaves and flowers, it must be exposed to at least 3 hours of full sunlight per day. Low light conditions, coupled with cooler temperatures, may force the plant to fully mature before its shoots can reach the surface.
Your water snowflake plant will regularly strive to produce leaves that reach the surface. These typically last for up to 2 weeks, depending on water conditions, and may need to be cut down once they begin to decay. Individual leaves may be dropped off by the mother plant and should be removed if you wish to prevent the plant from spreading. Spent flowers should also be removed to prevent seeding. Though the plant is a perennial, many gardeners replace it with new stock every 5 years to maximize its showiness.
How to Winter Water Snowflake
Water snowflake is not a frost-hardy plant and will have to be either brought indoors or treated as an annual (particularly if you live outside of USDA zones 8 – 11). Once temperatures drop to below 7˚C (45˚C), transfer your potted plant to an indoor tank or basin. This should be situated in a frost-free room or a warm area of your greenhouse. You may opt to cut down its foliage prior to moving it indoors. Once temperatures begin to rise and the final frosts have thawed, the plant can be re-situated outdoors. Place it in a shallow area of the pond and gradually move your pot deeper once new shoots begin to form.
Is Water Snowflake Invasive or Toxic?
Water snowflake is non-toxic but can, unfortunately, grow to become invasive in mild climates and standing water conditions. Its capacity for vigorous growth and rapid spread has caused it to be a nuisance plant in some areas of the US, such as Hawaii, Texas, and Florida. N. indica is also known for being a weed in several rice paddy systems in Asia. Its seeds, which are easily dispersed by water and live vectors (e.g. humans, waterfowl, mammals) can persist for a few years. In areas where water snowflake populations have spread considerably, herbicides have been tested for their efficiency in quelling plant growth.
When populations are uncontrolled or restricted, the floating leaves of this plant can form mats and block out sunlight. This results in low-oxygen conditions and the reduction of water flow. Consequently, floating debris can become trapped, stimulating bacterial growth and suffocating other aquatic plants. In some cases, summer tourism and boating industries are impacted as the floating mats can impede water recreational activities.
Where to Buy Water Snowflake & Seeds? (UK & US)
Nymphoides indica can be purchased as bare-rooted plants from plant nurseries and aquascaping shops across its native range. They may be quite difficult to find in states where the plant is deemed invasive. Do check your state’s quarantine requirements or forbidden plants list if you intend to purchase this species online. You may opt for other Nymphoides species, which tend to have similar leaves and flowers, if unable to obtain this one. Be aware that many ornamentally grown varieties (e.g. Nymphoides peltata, Nymphoides cristata) unfortunately have a similar capacity for invasiveness.
Can you cut the roots of the snowflake when its too long?