arrowleaf tearthumb (Polygonum sagittatum)
Persicaria sagittata (L.) Gross.
Polygonum sagittatum L. var. gracilentum Fernald
Tracaulon sagittatum (L.) Small
Tracaulon sagittatum (L.) Small var. gracilentum (Fernald) C.F. Reed
Truellum sagittatum (L.) Soják
CONFIRMATION STATUS: Pending confirmation.
TAXONOMY: The currently acccepted scientific name for arrowleaf
tearthumb is Polygonum sagittatum L. This species is listed as Persicaria sagittata in the Flora of Virginia.
NATIVE STATUS: Native, United States and Canada.
GENERAL BOTANICAL CHARACTERISTICS:
Habit: Arrowleaf tearthumb is is an annual vine/herb that grows 6-18
inches tall and 3-6' long, often simple to extensively branched. Initially
climbing with upright stems, it generally develops a more prostrate habit,
becoming reclining or sprawling, tending to fall over and climb over ad-
jacent vegetation or itself, creating a tangle of stems and leaves. The
stems are light green to green, yellowish green, or becoming red to red-
dish purple at maturity. Stems are strongly angular, upright 4-sided and
ribbed, slender and weak. Stems are glabrous with many prickles turned
oppositely (retrorsely barbed) from the direction of the stem. Stem nodes
are swollen with an ohrea present.
Leaves: Leaves are alternate and widely spaced along the stems. The leaf
blades are up to 4" long and 1" across. They are narrowly arrow-like (sag-
ittate) in shape and their margins are smooth and slightly ciliate with stiff
hairs. The upper blade surfaces are medium green and hairless, while their
lower surfaces are pale green and slightly prickly along their central veins.
The leaves are sessile or they have petioles up to 1" long. Near the base of
each petiole, there is an oblique membranous sheath (ochrea) that wraps
around the stem, give the leaves even more of an arrowhead appearance.
This sheath is largely devoid of hairs and prickles, often weakly ciliate at
tip, lower ones often lacerate.
Flowers: Both terminal and axillary flowers are produced on short spike-
like racemes. The racemes are spherical or ovoid-spherical in shape and
up to ½" long; they are produced individually or in pairs on long naked
peduncles up to 6" long. The flowers are densely arranged along each
raceme. Individual flowers are about 1/8" long, consisting of 5 white to
pink tepals, 8 short stamens, inserted at base of perianth in 2 whorls, and
an ovary with a tripartite style. At the base of each raceme, there is a pair
of small green bracts. Similarly, at the base of each flower, there is a pair
of tiny bracts that are greenish yellow and ovate.
Fruit/Seeds: Each flower is replaced by a single dark brown to black,
dull to shiny nutlet that is about 3 mm. long, ovoid, and bluntly 3-
Roots: Arrowleaf tearthumb can form rootlets where the stems are de-
cumbent on moist open ground.
REGENERATION PROCESS: Arrowleaf tearthumb propogates itself
HABITAT TYPES: Arrowleaf tearthumb is found in a variety of wetland
habitats, including marshes, swamps, shorelines, river and creek banks,
recently burned bogs, gravelly seeps, low areas along springs, and soggy
SITE CHARACTERISTICS: Arrowleaf tearthumb prefers partial sun,
wet to moist conditions(temporary flooding is tolerated) , and soil contain-
ing silty loam, sand, gravel, or peat moss.
SEASONAL DEVELOPMENT: The blooming period occurs from mid-
summer into the fall (June into October) and lasts about 2-3 months.
GENERAL DISTRIBUTION: Arrowleaf tearthumb naturally occurs in
all the eastern states and provinces, from Florida north into the Canadian
maritime provinces, and west to Texas north into Manitoba. It also occurs
in Colorado and Oregon, but is not naturally found in the far southwestern
states, most of the the American and Canadian Rocky Mountain states and
provinces, the far western and northwestern states and provinces.
SKY MEADOWS DISTRIBUTION: To be determined.
IMPORTANCE AND USES: The floral-faunal relationships of arrow-
leaf tearthumb are similar to Persicaria spp. (Smartweeds). The nectar
and pollen of the flowers attract primarily small bees, wasps, and flies.
The leaves are eaten by the caterpillars of the butterflies Lycaena helloides
(purplish copper) and Lycaena hyllus (bronze copper), while the flowers
and developing seeds are eaten by the caterpillars of the butterfly Strymon
melinus (gray hairstreak). Other insects that feed on this plant include flea
beetles, aphids, stinkbugs, and the caterpillars of several moths. Various
species of birds that occur in wetlands eat the seeds; these include Mallards
and other dappling ducks, some rails, and granivorous songbirds (e.g., bobo-
link, swamp sparrow, redwing blackbird). Because it often forms dense
tangles of prickly stems and leaves, arrowleaf tearthumb provides protec-
tive cover for various kinds of wildlife.
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