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Elodea densa

(Planch.) Casp. (1857)

This name is accepted

Kingdom: Viridiplantae Phylum: Magnoliophyta Class/Clade: Monocots Order: Alismatales Family: Hydrocharitaceae Genus: Elodea

anacharis, ditch moss

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Description

Key Characters:

Growth Form: Aquatic herbs.

Stems: Stems terete (cylindrical), 2–3 mm in diameter.

Roots:

Leaves: Leaves simple. Leaves in whorls of 3. Blades ovate or narrowly ovate, 3–7 mm long, 1.5–2 mm wide, middle and upper leaves in whorls of 4–5, oblong to linear, 12–40 mm long, 1.7–5 mm wide. Margins serrulate. Sessile. Stipules absent.

Flowers: Flowers above water at anthesis, insect–pollinated, unisexual (and the plants dioecious). Sepals 3, green, smaller than petals, 3-4 mm long in male flowers. Petals 3, white, up to 9-12 mm long in male flowers. Staminate flowers borne in spathes in the upper leaf axils, 11–12 mm long, on a long thread-like hypanthium 30–60 mm long. Ovary likely inferior, pistillate flowers not seen.

Fruit: Unknown. Seeds without endosperm.

Ploidy: 2n = 2n =48

Habitat: Sparingly naturalized in ponds and perhaps also slow–running ditches.

Elevation Range:

Historical Distribution

Images

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Uses and Culture

USES

  • Yes

Natural History

Statewide Status

Naturalized

Island Status

Kaua'i Naturalized
O'ahu Naturalized
Molokai Not in flora
Maui Naturalized
Hawai'i Naturalized

Dispersal Agents


Pollinators

Bibliography

Name Published In: Monatsber. Königl. Preuss. Akad. Wiss. Berlin 1857: 49 (1857)

Other References

Wagner et al. 1990:1443 (K, O, Mo, H [as Egeria densa]); Oppenheimer 2003:14 (WM); Staples & Herbst 2005:666 (DESCR); Bernardini & Lucchese 2018/POWO 2025 (Syn. Egeria densa = Elodea densa); Faccenda, Arthur, et al. 2025:186 (remove Mo [no evidence of nat.])

Occurrences

SNo. Scientific Name Locality Habitat Basis of Record Description Recorded By Record Number Island Source Date
1 Elodea densa Cultivated in water pot, Keolu Hills, Kailua, Oahu, Hawaii Cultivated, Water pot, Kailua home. Preserved_Specimen Submerged long, dark translucent green herb, sessile leaves, very few branching, white flower, emergent from water. Crago, L.M. 2005131 Oahu BISH 2005-05-09
2 Elodea densa Koloa District, Hanapepe River at Ho Rd crossing, Hanapepe Rooting in 0.3-0.6 m water. Preserved_Specimen Submerged aquatic forming dense populations. Lorence, D.H. 5205 Kauai BISH 1987-05-05
3 Elodea densa Hawaii Volcanoes National Park Abundant in fresh water pond back of dunes. Preserved_Specimen Loosely rooted or floating, flowers white, emersed. Fosberg, F.R. 53709 Hawaii BISH 1971-04-14
4 Elodea densa Hilo, Wailoa Stream near Kapiolani School Abundant supply. Preserved_Specimen Kashiwamura, V. Hawaii BISH 1993-12-06
5 Elodea densa Hilo Choking pool. Preserved_Specimen Plants up to 18 ft long, female flowers. Ewart III, G.R. Hawaii BISH 1937-11-03
6 Elodea densa Kaneohe Stream, in shallow, fast-running section of stream Forming thick mats underwater along with Vallisneria americana and an unidentified matted Alismataceae (Imada et al. 2001-44). Preserved_Specimen Imada, C. 200143 Oahu BISH 2001-06-05
7 Elodea densa Hamakua District, Kukuihaele quad, Waipio Valley, area of Wailoa Stream nearest Naalapa Falls Common submerged aquatic herb in Wailoa Stream. Preserved_Specimen Flowers white, raised above water on a thin peduncle. Imada, C. 200119 Hawaii BISH 2001-03-13
8 Elodea densa Hilo Choking pool. Preserved_Specimen Plants up to 18 ft long, female flowers. Ewart III, G.R. Hawaii BISH 1937-11-03
9 Elodea densa Blue Hole drainage, end of Kuamoo road still pool makai of start of irrigation ditch Preserved_Specimen aquatic herb, dense mats; leaves translucent Trauernicht, C. 744 Kauai BISH 2009-02-12
10 Elodea densa Honolulu Cultivated in Aquaria. Preserved_Specimen St.John, H. 11629 Oahu BISH 1932-04-24
11 Elodea densa Honolulu Distr., Makiki Stream, in channelized section at intersection of Kalakaua Ave. and South King St Associated with alien riparian vegetation, including Hydrilla, Amaranthus. Preserved_Specimen Submerged aquatic, occasional, rooted in substrate. Imada, C. 200154 Oahu BISH 2001-08-19
12 Elodea densa Kailua, Kawainui Marsh, in slow-moving waterway on ranchlands of Martin Knott adjacent to ranch entrance Preserved_Specimen Very abundant submerged herb choking the waterway. Flowers white, arising on short stalks above water surface. Imada, C. 20007 Oahu BISH 2000-06-08
13 Elodea densa Honolulu International Airport; aquatic plants from Singapore Preserved_Specimen Lvs in whorls of 4; no scales at nodes; flrs white, borne above water surface; bunch plants (tip cuttings 8-10 long); no roots; only 1 flw-long peduncle; petals ca 1/4 broad, white. Hoe, W.J. 507 Oahu BISH 1989-11-14
14 Elodea densa Honolulu Preserved_Specimen Lvs deep grn. Hoe, W.J. 564 Oahu BISH 1990-03-06
15 Elodea densa W Maui, Lahaina District, Olowalu In reservoir. Preserved_Specimen Oppenheimer, H.L. 110002 Maui BISH 2000-11-04
16 Elodea densa Pond below Kupelau Gulch Preserved_Specimen Wilbur, R.L. 290 Oahu BISH 1947-11-06
17 Elodea densa Kaneohe Stream adjacent to Kaneohe Library Preserved_Specimen Forming dense patches rooted to the substrate in fast-running fresh water. Growing with Vallisneria americana and an unidentified Alismataceae (Imada & Preston 2001-25). Imada, C. 200127 Oahu BISH 2001-05-10
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