Zannichellia palustris

This is a submerged aquatic plant about ¾-3' long that branches occasionally; it is a perennial. The weak stems are light green, glabrous, and filiform (about 0.5 mm. across). The leaves are arranged oppositely or in pseudo-whorls at intervals along these stems; they are 1-3" long and 0.5-1.0 mm. across. The leaves are light to medium green, linear in shape and flattened, smooth along their margins, and glabrous, tapering to acute tips. The stems and leaves often darken with age or become brown from a coating of algae. Membranous sheaths surround the stems at the bases of the leaves; these delicate sheaths disintegrate with age. Horned Pondweed is monoecious, producing separate male (staminate) and female (pistillate) flowers on the same plant. These inconspicuous flowers are located at the bases of the leaves, where male and female flowers often occur together. Male flowers occur individually; each male flower consists of a single stamen. Female flowers occur in groups of 1-5; each female flower consists of an ovary with a style and a peltate stigma. Neither male nor female flowers have petals and sepals. The blooming period can occur from late spring into the summer. Cross-pollination of the flowers occurs underwater. Fertile female flowers are replaced by beaked fruits about 3.0-3.5 mm. in length. Each slightly flattened fruit has a curved-ovoid shape that is convex and occasionally crested on one side and either straight or slightly concave on the other side. The beak of each fruit is prominent. The fruits usually have short pedicels (0.5-1.0 mm. in length) or they share a short peduncle (0.5-1.0 mm. in length). Each fruit contains a single achene that is distributed by water. The root system is fibrous and rhizomatous. Clonal colonies of plants often develop from the rhizomes.

The native Horned Pondweed is occasional in northern and west-central Illinois, while in the rest of the state it is uncommon or absent. In addition to North America, this aquatic plant also occurs in Eurasia and other continents. Habitats include marshes with open water, springs and streams, drainage canals, small ponds, and protected inlets of lakes. Outside of Illinois, this plant can be found in brackish marshes and bays.

Polish Exclusive Economic Zone, Swedish Exclusive Economic Zone

Nile region, oases, Mediterranean region and Egyptian desert.     

Cosmopolitan.

Zannichellia palustris var. pedicellata Fr.:
Argentina (South America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Zannichellia palustris var. repens Koch:
Argentina (South America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Zannichellia palustris var. major Koch:
United States (North America)
Canada (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Zannichellia palustris subsp. pedicellata Wahlenb. & Rosen:
Sweden (Europe)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Zannichellia palustris L.:
Chile (South America)
Canada (North America)
Pakistan (Asia)
Brazil (South America)
China (Asia)
United States (North America)
Argentina (South America)
Peru (South America)
Bolivia (South America)
Mexico (Mesoamerica)
Colombia (South America)
Madagascar (Africa & Madagascar)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Alta., B.C., Man., N.B., Nfld. and Labr. (Nfld.), N.W.T., N.S., Ont., P.E.I., Que., Sask.; Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Del., D.C., Fla., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Oreg., Pa., R.I., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Mexico; West Indies; Central America; South America; Eurasia; Africa; Australia.

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

United States

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

Global Range: Cosmopolitan.

Distribution: A cosmopolitan species.

Leaves linear, opposite or in whorls. Peduncle of the inflorescence 1-1.5 mm long. Male and female flowers subsessile; pedicels 0.5-1 mm. style very short in flower, 2-2.5 mm in fruit; stigma peltate, wavy; achenes 2-5, stalked; stalk 1-1.5 mm long, back of the achene curved and dentate.

Herbs entirely submersed. Stems to 50 cm ´ 0.2----0.6 mm. Leaves 3.5--4.2 cm ´ 0.2--1 mm, apex acute. Staminate flowers: filament 1.5--2 mm, connective prolonged into blunt tip 0.1 mm. Pistillate flowers: pistils 4--5; style 0.4--0.7 mm. Fruits 1.7--2.8 ´ 0.6--0.9 mm; rostrum 0.7--2 mm; podogyne 0.1--1.5 mm; pedicel 0.3--1.2 mm.

The native Horned Pondweed is occasional in northern and west-central Illinois, while in the rest of the state it is uncommon or absent. In addition to North America, this aquatic plant also occurs in Eurasia and other continents. Habitats include marshes with open water, springs and streams, drainage canals, small ponds, and protected inlets of lakes. Outside of Illinois, this plant can be found in brackish marshes and bays.

Fresh and brackish water in canals and drains.

Brackish or fresh waters of streams, lakes, or estuaries; 0--2900m.

Depth range based on 4 specimens in 1 taxon.

Environmental ranges
  Depth range (m): 2 - 2
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Comments: Brackish and fresh water.

The foliage of Horned Pondweed is probably consumed by some aquatic insects, but information is currently lacking. Waterfowl consume the foliage and seeds of these plants

Foodplant / feeds on
larva of Macroplea mutica feeds on root of Zannichellia palustris
Remarks: Other: uncertain

Flowering spring--summer.

Fl. Per. February-March.

Annual or perennial.

The following is a representative barcode sequence, the centroid of all available sequences for this species.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 9
Specimens with Barcodes: 9
Species With Barcodes: 1

Canada

Rounded National Status Rank: N4 - Apparently Secure

United States

Rounded National Status Rank: NNR - Unranked

Rounded Global Status Rank: G5 - Secure

Reasons: Widespread cosmopolitan species with many thousands of occurrences.

The preference is full or partial sun, shallow water up to 4' deep, and a bottom that is mucky, sandy, or rocky. Either fresh or brackish water is tolerated if it is reasonably clear; the pH of the water can vary from mildly acidic to alkaline. Locations with strong currents or wave action should be avoided.