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Pistia stratiotes

Water Lettuce

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Image:	Leaves	55KB

General Information

COMMON NAMES: Water Lettuce, Shell Flower

GLOBAL DISTRIBUTION: NATIVE e.Africa (possibly Lake Victoria); EXOTIC EXOTIC pantropical

COOK ISLANDS STATUS: Introduced - Recent, Naturalised; S.Group only (RR only - uncommon); Freshwater, wetlands - ponds; prefers shallow water where roots can reach the mud.

SIGNIFICANCE LIST: Ornamental leaves; Potential weed of waterways

KEY FEATURES: Free-floating herb to 30cm high. ROOTS feathery. LEAVES rosette, downy and pale green, wedge-shaped to 15x8cm, tip blunt and notched, 5-10 parallel ribs, with water-repellent hairs; spread during day, erect during night. FLOWERS inconspicuous. Spread by stolons which develop daughter rosettes of leaves.

Cook Islands Distribution

View Distribution Map

Southern Group: Present Makatea: -
RR	MG	AT	MK	MT	AK	PL	TK	MN
+	-	-	-	-	-	-	-	-

Northern Group: -
TN	MH	RK	PK	NS	SW
-	-	-	-	-	-

Key to Symbols

blank	no data
-	absent	L	localised
X	extinct 'naturally'	W	widespread
XQi	quarantine intercepted	R	recent
XQe	eradicated	?	query preceding category
P	present	T?	taxonomic query
S	seasonal	nn	present, said to have no name
O	occasional	?1	present, name not investigated
++++	very common	?2	presence not verified, no name recorded
+++	common	N/A	absent, name not expected
++	uncommon
+	rare
Cook Islands islands: RR =Rarotonga, MG = Mangaia, AT =‘Ātiu, MK=Ma‘uke, MT=Miti‘āro, AK=Aitutaki, PL=Palmerston, PN=Penrhyn, MN=Manuae, TK=Takūtea, TN=Tongareva (TS=Tongaleva Spoken, TW=Tongareva Written, they say "el" but write "r"), MH=Manihiki, RK=Rakahanga, PK=Pukapuka, NS=Nassau, SW=Suwarrow. After a Polynesian name: ^=orthography query. Countries and other: FIJ=Fiji, WT=Wallis & Futuna, SAM=Samoa, TON=Tonga, NIU=Niue, CK=Cook Islands, CKM=Cook Islands Māori, FP=French Polynesia, AUS=Australs, SOC=Societies, TAH=Tahiti, TUA=Tuamotus, MQS=Marquesas, MNG=Mangareva, PIT=Pitcain group, EAS=Easter Island, HAW=Hawai‘i, NZ=New Zealand, NZM=New Zealand Māori

Scientific Taxonomy

Pistia stratiotes Linnaeus
TAXONOMY: PLANTAE; ANTHOPHYTA (=Angiospermae); LILIOPSIDA (=Monocotyledones); ARECIDAE; Arales; ARACEAE

More Information

SIGNIFICANCE NOTES -
POSITIVE SIGNIFICANCE: Ornamental leaves
NEGATIVE SIGNIFICANCE: Potential weed of waterways. Comments: Naturalised in ditches, ponds and watercourses in Hawaii.

Vouchers & References

Vouchers:
None Recorded.

References:
p.1359 Wagner et al.- Flowering Plants of Hawaii
p.164 Neal - In Gardens of Hawaii
p.879 Hortus 3rd
p.901 Royal Hort. Soc. Index of Garden Plants
p.129 Tropica

Data Update History (information):
zTX, zB02, zM03a, zD02

Web Resources

Citation Information

McCormack, Gerald (2007) Cook Islands Biodiversity Database, Version 2007.2. Cook Islands Natural Heritage Trust, Rarotonga. Online at http://cookislands.bishopmuseum.org.
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