This perennial wildflower is usually an emergent aquatic that is exerted 1-3' above the water line, otherwise it is a terrestrial plant of similar height. The stems are usually unbranched, although larger plants are sometimes branched below. The stems are light green, angular-terete, and glabrous. At intervals along each stem, there are pairs of opposite leaves about 2-6' long and ¼-1' across that are either sessile or short-petioled. The deciduous leaves are narrowly lanceolate, linear-lanceolate, elliptic, or narrowly elliptic in shape and usually smooth along their margins. Less often, the outer margins may be slightly undulate or shallowly crenate. Both the upper and lower surfaces of the leaves are medium green and glabrous. From the axils of the middle to upper leaves, there develops individual spikes of flowers on long peduncles. Each floral spike is about 1' long and capitate (head-like) in appearance; there are several overlapping flowers and buds per spike. Each flower is about ¾' across, consisting of a short-tubular corolla with 4 lobes, a short-tubular calyx with 5 teeth, 2 stamens with dark purple or dark brown anthers, and an ovary with a slender white style. The corolla has a shallowly notched upper lobe that curves backward, 2 lateral lobes that are widely spreading, and a lower lobe that curves slightly downward. Except for the dark purple mottling at the base of the lower lobe, the lobes are mostly white, otherwise they are tinted pale purple or they are lightly speckled with fine purple dots. The lobes of the corolla are longer than the corolla tube, and they are oblong to oblong-oblanceolate in shape. The green calyx is about ¼' long and glabrous; its teeth are narrowly lanceolate. The ascending straight peduncles are a little shorter to about as long as the leaves (up to 6' in length); they are  medium green, angular, and glabrous. The blooming period occurs from early summer into the fall, lasting about 2-4 months. Usually, only a few flowers are in bloom at the same time. Afterwards, the flowers are replaced by seed capsules up to ½' long that taper to stipe-like bases. Each capsule has 2 cells, and each cell contains 2 seeds. The seeds are about 1/8' (3 mm.) in length and warty. The root system is highly rhizomatous, forming colonies of plants.

The native Water Willow is occasional in most areas of Illinois, except the NW section of the state, where it is uncommon or absent (see Distribution Map). Habitats include sandbars, gravelbars, or mudbars of rivers, low islands in rivers or ponds, shallow water or muddy banks of ponds and rivers, shallow water of rocky upland streams, shallow water or wet areas of swamps, and sandy marshes. Water Willow occurs in wetlands with either stagnant water or slow to moderate currents of water.

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Dianthera americana L.:
Canada (North America)
United States (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.

Justicia americana var. subcoriacea Fernald:
United States (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.

Justicia mortuifluminis Fernald:
United States (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.

Justicia americana (L.) Vahl:
Canada (North America)
United States (North America)
Mexico (Mesoamerica)

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.

The native Water Willow is occasional in most areas of Illinois, except the NW section of the state, where it is uncommon or absent (see Distribution Map). Habitats include sandbars, gravelbars, or mudbars of rivers, low islands in rivers or ponds, shallow water or muddy banks of ponds and rivers, shallow water of rocky upland streams, shallow water or wet areas of swamps, and sandy marshes. Water Willow occurs in wetlands with either stagnant water or slow to moderate currents of water.

The flowers are cross-pollinated primarily by bees, including honeybees, bumblebees, Anthophorine bees (Anthophora spp.), Little Carpenter bees (Ceratina spp.), Cuckoo bees (Epeolus spp., Triepeolus spp.), Digger bees (Melissodes spp., Synhalonia spp.), Leaf-Cutter bees (Megachile spp.), Green metallic bees, and other Halictid bees. Other floral visitors include various wasps, bee flies (Bombyliidae), Thick-headed flies (Conopidae), Syrphid flies (non-pollinating), small butterflies, and skippers. These insects obtain primarily nectar from the flowers, although some bees collect pollen and some flies feed on pollen. Water Willow is one of the host plants for the caterpillars of Darapsa versicolor (Hydrangea Sphinx); they feed on the foliage. This plant is also a minor source of food for Muskrats.

Justicia americana (Water Willow)
(Most bees suck nectar; some bees collect pollen as indicated below; flies and beetles suck nectar or feed on pollen; other insects suck nectar; most observations are from Robertson, otherwise they are from Conger and Estes & Thorp as indicated below)

Bees (long-tongued)
Apidae (Apinae): Apis mellifera fq; Apidae (Bombini): Bombus griseocallis sn fq, Bombus impatiens sn, Bombus pensylvanica sn; Anthophoridae (Anthophorini): Anthophora abrupta sn fq; Anthophoridae (Ceratinini): Ceratina dupla dupla sn fq; Anthophoridae (Epeolini): Epeolus bifasciatus sn, Triepeolus lunatus concolor sn; Anthophoridae (Eucerini): Florilegus condigna sn fq, Melissodes bimaculata bimaculata sn fq, Melissodes communis sn , Synhalonia dilecta sn , Synhalonia rosae sn; Anthophoridae (Nomadini): Nomada articulata sn; Megachilidae (Coelioxini): Coelioxys octodentata sn, Coelioxys sayi sn fq; Megachilidae (Megachilini): Megachile addenda sn cp, Megachile brevis brevis sn, Megachile latimanus sn/cp (Cng), Megachile montivaga sn, Megachile pugnatus sn, Megachile texana sn; Megachilidae (Osmiini): Hoplitis cylindricans sn cp, Hoplitis pilosifrons sn cp fq, Osmia distincta sn

Bees (short-tongued)
Halictidae (Halictinae): Agapostemon sericea sn (Rb, Cng), Agapostemon virescens sn, Augochlorella aurata sn, Augochlorella striata sn cp fq, Halictus confusus sn, Halictus ligatus sn, Halictus rubicunda sn fq, Lasioglossum imitatus sn cp, Lasioglossum lustrans sn (ET), Lasioglossum pilosus pilosus cp, Lasioglossum versatus sn cp fq; Andrenidae (Andreninae): Andrena sp. sn/cp (Cng); Andrenidae (Panurginae): Calliopsis andreniformis sn fq

Wasps
Sphecidae (Bembicinae): Bembix americana sn, Microbembex monodonta sn fq (Cng); Sphecidae (Sphecinae): Ammophila nigricans sn; Scoliidae: Campsomeris plumipes sn

Flies
Syrphidae: Allograpta obliqua fp np, Eristalis tenax sn fp, Parhelophilus laetus fp np, Sphaerophoria contiqua fp np, Syritta pipiens sn (Rb, Cng), Toxomerus marginatus fp np, Tropidia quadrata sn (Rb, Cng); Bombyliidae: Bombylius atriceps sn fq, Bombylius helvus sn, Rhynchanthrax parvicornis sn; Conopidae: Physocephala tibialis sn, Zodion fulvifrons sn; Calliphoridae: Lucilia illustris sn/fp (Cng)

Butterflies
Nymphalidae: Chlosyne nycteis sn; Lycaenidae: Celastrina argiolus sn; Pieridae: Pieris rapae sn (Rb, Cng)

Skippers
Hesperiidae: Epargyreus clarus sn, Erynnis martialis sn, Euphyes vestris sn, Thorybes bathyllus sn

Beetles
Scarabaeidae: Anomala lucicola sn/fp (Cng)

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


No available public DNA sequences.

Download FASTA File

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 2
Specimens with Barcodes: 2
Species With Barcodes: 1

Canada

Rounded National Status Rank: N2 - Imperiled

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

The preference is full or partial sun, shallow standing water (up to 3' deep) or wet conditions, and soil that is muddy, sandy, or gravelly.