Pontederia cordata L.

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Common names:
pickerel weed, pickerelweed
Synonyms:
Pontederia cordata L. var. angustifolia (Pursh) Torr. & Elliott; Pontederia cordata L. var. lanceolata (Nutt.) Griseb.; Pontederia cordata L. var. lancifolia (Muhl. ex Elliott) Torr.; Pontederia lanceolata Nutt.
Description:
Growth form:
Perennial aquatic herb,
Size:
15 cm - 1.2 m tall.
Stems
of two types: rhizome-like, contracted, vegetative stems, which are submersed underwater; and erect, flowering stems, which are slightly constricted just below the first node.
Leaves
of two types: a basal rosette of stalkless, linear leaves, which are normally underwater; and emergent, stalked (up to 60 cm), lance- to heart-shaped, 6 - 22 cm long, 0.7 - 12 cm wide stem leaves with a 7 - 29 cm long stipule. The leaf stalks of the emergent leaves are distinctly constricted just below the blades. Veins of leaf blades all parallel, curved, and never with netlike veins between them.
Inflorescence
a long-stalked, elongate spike (2 - 15 cm long) of fifty to several hundred, stalkless flowers. The inflorescence stalk is glandular-hairy or long, silky-hairy, and the upper part of the stalk has a 5 - 17 cm long bract folded around it.
Flowers
numerous, stalkless, mauve, 4 - 12 mm long, 1 - 1.6 cm wide, bilaterally symmetric, two-lipped, but generally funnel-shaped with spreading lobes. The flowers are only open for one day.
Tepals
six, but fused into a 3 - 9 mm long tube, then separating into 5 - 8 mm long, inversely lance-shaped, pointy-tipped lobes, which together appear as an upper three-lobed lip, and a lower three-lobed lip. The tepals are covered with glandular or long, silky hairs, and while all tepals are mauve, the upper, central lobe has a distinctive, two-lobed, yellow spot.
Stamens
six, but of two lengths: the upper three short (1.5 - 6.3 mm long), and the lower three longer (0.7 - 1.3 cm long). Filaments purple, and glandular-hairy. Anthers yellow, and egg-shaped to oblong.
Pistil
with one, three-chambered, superior ovary; and one, three-lobed style.
Fruit
a spike of numerous, single-seeded, single-chambered, egg-shaped, 4 - 6 mm long, 2 - 3 mm wide, bladder-like units (utricles), which have longitudinal, toothed ridges.
Help:
Plant Glossary
Similar species:
If only the leaves of Pontederia cordata are present, it could possibly be mistaken with some other common aquatic herbs such as Alisma triviale, A. subcordatum, Echinodorus berteroi, or even Sagittaria rigida and S. graminea, but all the leaves of those species have netlike veins running between the major lengthwise parallel veins. Once flowers are present, those species are rather unlike P. cordata because they have stalked flowers, many have branched inflorescences, and all have three obvious and separate sepals, three petals, and at least six pistils that form small or large fruiting heads of achenes. Another broad-leaved aquatic plant that is more closely related to P. cordata (in the same family) is the aggressive invasive Eichhornia crassipes, or water hyacinth. This species has been reported in the Chicago Region a few times, but it cannot survive through the winters. It differs from P. cordata by having more rounded and very leathery leaf blades, very inflated and almost bladder-like leaf stalks, larger flowers (over 2 cm wide), and capsules for fruit.
Flowering:
June to September
Habitat and ecology:
Somewhat rare, close to shores and in shallow water of lakes and slow-moving streams, also in shallow open water of bogs.
Regional occurrence:
native
Notes:
This is the only species of Pontederia in North America, and it extends south into Mexico, Central America, and South America. There can be much variation in leaf shape within populations and even on single plants.
Etymology:
Pontederia cordata
vPlants
name code: POCO14 ; page author: The Field Museum ; page date: 2010-03-15
Further information (external links):
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References:
Horn, C. N. 2002. Pontederia. In Magnoliophyta: Liliidae: Liliales and Orchidales. Vol. 26 of Flora of North America north of Mexico. ed. Flora of North America Editorial Committee, 45 - 46. New York: Oxford University Press.

Information provided on this page applies to the Chicago Region and may not be relevant or complete for other regions.

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