A small constructed pond sits on the low side of UBC Botanical Garden’s EH Lohbrunner Alpine Garden. This pond was absolutely “hopping” (bad pun intended) with activity on a hot day during an unusually dry July. Many Pacific tree frogs (Hyla regilla (PDF) were sunning themselves on the leaves of Nymphoides peltata. In the water were hundreds of tadpoles nearly ready to join them.
The frogs were a treat to see, but other signs of wildlife around the pond reminded me of the ecological importance of water. As I approached the pond’s edge, I initiated a flurry of activity as water striders, birds and bees hurried to move away. For my part, I had to watch out for the coyote scat that lay along the mossy bank. This small pond is clearly an important source of refreshment in a region that is experiencing “drought level 4” (a level of drought at which the water supply is insufficient to meet ecosystem and socioeconomic needs).
This species, also known as yellow floating heart, is often planted by North American water gardeners. It is easy to grow in shallow ponds that have little moving water (the second photograph by Daniel shows it growing in a pond in Vancouver, Canada’s Queen Elizabeth Park). The heart-shaped leaves display slightly different hues of green, and I find the pattern that they create as they sit just at the water’s surface very calming. And of course, there are the inflorescences. These are bright yellow and held about 3 cm above the water by stalks that each support two to five flowers. The five petals have a delicate fringe along their margins. Each flower blooms for one day. Van der Velde and Van der Heijden (1981) explain that the development of flowers occurs in a sequence, so that each Nymphoides peltata stand blooms over a long period of time (June to October).
Nymphoides peltata produces capsules with numerous floating seeds that can spread downstream. It can also reproduce vegetatively from stems, roots, and even leaves. Unfortunately, in many parts of North America, cultivated Nymphoides peltata have escaped into the wild. It is considered an invasive species in many states of the USA as well as in the Canadian provinces of Ontario and Quebec.
In its native range of temperate Europe, temperate Asia, and a bit of subtropical Asia, Nymphoides peltata plays an important role in its ecosystem. Its long flowering period and ability to form large stands makes it crucial to many pollinator species (see 1981 article linked above). Despite its weediness in North America, Nymphoides peltata is considered a vulnerable species in Japan, where it once commonly grew wild. Takagawa et. al. 2005 found that only one Japanese population, in Lake Kasumigaura, retains the potential for sexual reproduction.