Source: Wikimedia Commons
Water poppy
BeginnerHydrocleys nymphoides
A South American floating-leaved plant with round leaves that produces a succession of one-day, poppy-like yellow flowers. Called mizuhinageshi in Japanese. Cold-sensitive and listed as an alien species under consideration for control, so keep it out of the wild.
About
Water poppy (Hydrocleys nymphoides), known in Japan as mizuhinageshi, is a floating-leaved perennial of the Alismataceae. It is widespread in South and Central America and, grown widely as an ornamental, has naturalised in Australia, New Zealand, South Africa, the southern United States and elsewhere. Rooted in the bottom, it floats round leaves on the surface and spreads by stems that root and form new plants at their nodes. It grows in water up to 30–38 cm deep but prefers about 15 cm, and one plant can spread about 1.5 m across. It was introduced to Japan in the early Showa era and is locally naturalised in Kanagawa, Hyogo, Kagawa, Kochi and Miyazaki. The Ministry of the Environment's 2nd edition list (September 2026) places it among alien species under consideration for control. It is cold-sensitive and said to overwinter only in southern Japan. Popular for biotopes and water-lily bowls, it is widely sold in Japan.
Size of the Water poppy
The Water poppy grows to One plant can spread about 1.5 m across; prefers water about 15 cm deep.
Temperature & humidity for the Water poppy
Each flower lasts only a day, but they appear over a long season once the water reaches about 21°C.
Basic Info
Origin
South and Central America
Lifespan
Perennial; easily killed by cold
Size
One plant can spread about 1.5 m across; prefers water about 15 cm deep
Temperature
20〜28℃
Watering & Fertilizer
Feeds through roots in the soil
Growing Tips
Lighting
Grow outdoors in a sunny spot.
CO2 & Fertilizer
No CO2 needed; plant in a pot sunk under water so it feeds from the soil.
Water Temperature & Quality
Flowers once water reaches about 21°C. Cold-sensitive: overwinter indoors in a shallow tub, kept moist and bright.
Substrate & Attachment
Best in about 15 cm of water and tolerates up to 30–38 cm; suits water-lily bowls and shallow biotope areas.
Trimming & Propagation
Plantlets form at the nodes of creeping stems; separate rooted ones to propagate and thin out as needed.
Cautions
Listed as an alien species under consideration for control. Where water connects to natural waterways, stop fragments from washing out; never release it.
Water poppy FAQ
QWhat is the growing difficulty level for Water poppy?
Beginner. A variety suitable for beginners. No special equipment or experience is required—you can grow it without problems by setting up a basic cultivation environment.
QHow large does Water poppy get?
The mature size of Water poppy is One plant can spread about 1.5 m across; prefers water about 15 cm deep. This may vary slightly depending on cultivation environment and individual differences.
QHow should I water and fertilize Water poppy?
Water poppy: watering & fertilizer — Feeds through roots in the soil. Aim for appropriate frequency and amount.
QWhat is the typical price for Water poppy?
The price of Water poppy varies significantly by variety, characteristics, size, and lineage. Please check GrowerDirect's price guide for the latest market information.
Last updated: September 23, 2026
References & Sources
Edited & verified by: GrowerDirect Editorial Team
The classifications, regulations, and growing data on this page are created and verified based on the primary information database below.
Taxonomy & Authority
Regulations & Conservation Status
Not listed in CITES (no match in Species+). Listed as an alien species under consideration for control (mizuhinageshi) in the Ministry of the Environment's 2nd edition list (September 2026). It is not a Specified Invasive Alien Species and may be sold and grown, but where cultivation connects to natural waters, fragments must not be allowed to wash out, and it must not be taken into areas important for biodiversity. Never dump it in rivers or ponds.
Sources: Species+ (CITES listing check) / Ministry of the Environment: List of Alien Species that may Damage Ecosystems / Ministry of the Environment: alien species list, plants (2nd ed.)
Regulations may change. Always verify the latest information with the relevant authorities.
Related Species
Find listings for this species
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