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Polygonum persicaria L.

Lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley

KingdomPlantaePlants, but not fungi, lichens, or algae
SubkingdomTracheobiontaVascular plants—plants with a “circulatory system” for delivering water and nutrients
DivisionMagnoliophytaFlowering plants, also known as angiosperms
ClassMagnoliopsidaDicotyledons—plants with two initial seed leaves
SubclassCaryophyllidaeCacti, many other succulents, carnivorous plants, and leadworts
OrderCaryophyllalesIncludes cacti, carnations, amaranths, ice plants, and many carnivorous plants
FamilyPolygonaceaeKnotweed or smartweed family
GenusPolygonumGreek poly, “many,” and gonu, “knee,” for the swollen jointed stems
SpeciespersicariaFrom persica, “peach-like,” and sagittata, “barbed or arrow shaped,” for the leaf shape. This is the medieval name for knotweed

About plant names...

Lady’s thumb, a native of Europe and Asia, became naturalized throughout the entire United States after its introduction there. It is an annual. It colonizes disturbed soils that are wet or seasonally wet, such as ditches, pastures, grain fields, and water edges.

Plants: Up to 3' (91 cm) in height, though smaller plants are common. Stems are openly branched and often reddish.

Leaves: Alternate, lanceolate to elliptic, 1-8" (2.5-20 cm) long and ¼-2" (6.3-50 mm) wide. Leaf stems (petioles) are ⅛-¼" (5-8 mm) long. Leaves often have a dark purplish triangular or lunate patch on them. Leaf joints are covered by a papery sheath (ocrea) which is characteristic of this genus. Hairs extend up to ¹/₁₆" (2 mm) from the ocrea.

Flowers: Tiny pink and white flowers form groups of spikes ½-1½" (1.3-3.8 cm) long—the most noticeable feature of these rather inconspicuous plants. Flowers appear from June to July.

Fruits: Brown to black, glossy, with one seed. They are roughly egg-shaped, but somewhat angular. Each fruit is less than ¹/₁₆" (2 mm) long. Fruits appear from July to September.

Edibility: The leaves and young shoots are “palatable and nutritious.” Young leaves may be added to salads, or cooked and served with vinegar, tasting a bit like spinach.

Some similar species:

 

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

9/3/2009 · Nashua River Rail Trail, Ayer, Mass­a­chu­setts
≈ 5 × 5" (13 × 13 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

8/31/2013 · Riverside Park, James River, Midlothian, Virginia
≈ 6 × 4½" (15 × 12 cm) ID is uncertain

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

8/31/2013 · Riverside Park, James River, Midlothian, Virginia
≈ 8 × 5" (19 × 13 cm) ID is uncertain

 
Polygonum amphibium

Polygonum cespitosum

Polygonum hydropiperoides
Common Name

water smartweed

Oriental lady’s thumb

mild water-pepper
Plant Up to 9½' (3 m) × ⅜" (1 cm), sprawling or floating. Up to 3' (91 cm) in size, sprawling or erect. 6-39" (15-100 cm) long, but slender and with upper portions usually erect, erect to sprawling. Stems are green to red. (Compare to P. amphibium, with stems up to ⅜" (1 cm) around, and more often sprawled along the surface of the water).
Flowers Pink, appearing in a thick oval cluster of tiny five-lobed flowers. The cluster is ¾-6" (2-15 cm) long. Each individual flower is ⅛-³/₁₆" (4-5 mm) in diameter. Flowers appear June to September. Pink/white flower spikes are ¾-1½" (1.9-3.8 cm) tall × ¹/₁₆-³/₁₆" (3-6 mm) thick, densely filled with individual flowers less than ¼" (6.3 mm) in size. (By contrast, P. persicaria has flower stalks ⅛-⅜" (6-12 mm) thick.) Flowers appear from June to October. Greenish, pinkish, or white flowers form loose, elongated spikes 1-3" (3-8 cm) long and ¹/₁₆-⅛" (2-5 mm) around. The spikes are on peduncles ⅜-1" (1-3 cm) long.
Leaves Alternate, and often lanceolate, but they take on many other shapes. They may be floating or upright, with papery sheaths at leaf bases. They are ¾-8" (2-20 cm) × ⅛-1¾" (5-50 mm), with petioles ¹/₃₂-1" (1-30 mm). They are not mottled. Alternate, elliptic to lanceolate, ¾-3" (2-7.5 cm) × ⅜-1¼" (1-3.5 cm), and pointed at the base and tip. Petioles are ¹/₃₂-⅛" (1-5 mm). Leaves are not mottled. Alternate, lanceolate, bristly, with smooth edges. Floating or upright, up to 1¾-6" (5-15 cm) × ⅜-⅞" (1-2.5 cm), tapering to a sharp point. Petioles are less than ⅛" (5 mm) long. Leaves are not mottled.
Stem Ocrea are ⅛-1¾" (5-50 mm), with the upper part fringed with small hairs 0.5-4.5 mm long. Ocrea encompassing the joints are long-bristly, and ⅛-⅜" (4-12 mm) long,, vs. less than ⅛" (5 mm) for P. persicaria. Ocrea are brown, cylindric, and ⅛-⅞" (5-23 mm) long, with an inflated base, topped with hairs ¹/₁₆-⅜" (2-10 mm).
Fruit Tiny brown rounded achenes ¹/₁₆-⅛" (2.5-3 mm) long. Each achene contains one seed. They appear from July to September. A black achene with a triangular cross section. Dry, hard, smooth, shiny achenes each contain a single seed. They are ¹/₃₂-⅛" (1.5-3 mm) long, and three-sided.
Range/ Zones

Habitats Floating in ponds, streams, and marshes Common to invasive in disturbed habitats such as pastures, roadsides, and lawns. It is partial to wet areas. Often forming mats along lake or pond margins.
Type Wild Wild Wild

 

 
Polygonum lapathifolium
You are here
Polygonum persicaria
Common Name

nodding smartweed

lady’s thumb
Plant 24-60" (60-152 cm) high, usually upright, some­times sprawling, with green or deep red hairless stems. Up to 3' (91 cm) in height. Stems are openly branched and often reddish.
Flowers Greenish-white to pink, in columns about ¼-⅜" (6.3-9.5 mm) in diameter and 1-3" (2.5-7.6 cm) long. Numerous clusters may be upright, arched, or drooping. The tiny, individual flowers never actually open. Tiny pink and white flowers form groups of spikes ½-1½" (1.3-3.8 cm) long. Flowers appear from June to July.
Leaves Alternate, typically lanceolate but variable in shape, fatter at the base and tapering to a sharp tip, 1¾-10" (5-25 cm) × ½-1¾" (1.5-5 cm). Petioles are ⅜-¾" (1-2 cm). Leaves have tiny, hooklike hairs that make them feel rough. They are not mottled. Alternate, lanceolate to elliptic, 1-8" (2.5-20 cm) long × ¼-2" (6.3-50 mm) wide. Petioles are ⅛-¼" (5-8 mm). Leaves often have a dark purplish triangular or lunate patch on them.
Stem The ocreas are brownish, tubular, ½-1" (1.5-3 cm) long, with few or no hairs. Ocreas have hairs that extend up to ¹/₁₆" (2 mm) from the top.
Fruit Egg-shaped, less than ¹/₁₆" (2 mm) long, brown to black, glossy, containing a single seed. Brown to black, glossy, with one seed. They are roughly egg-shaped, but somewhat angular. Each fruit is less than ¹/₁₆" (2 mm) long. Fruits appear from July to September.
Range/ Zones

USDA Zones: 4-8
Habitats Margins of water bodies, pastures, orchards, irrigated crop fields, and rice fields. Disturbed soils that are wet or seasonally wet, such as ditches, pastures, grain fields, and water edges.
Type Wild Wild

 

Online References:

Polygonum persicaria at the Missouri Botanical Garden

Polygonum persicaria on CalPhotos

Polygonum persicaria at Alaskawildflowers.us

Polygonum persicaria on Turner Photographics' Wildflowers site

Polygonum persicaria on Plants for a Future, a resource and information centre for edible and otherwise useful plants

Polygonum persicaria on

Polygonum persicaria on wric.ucdavis.edu (PDF)

Polygonum persicaria on eFloras

References:

Peterson, Lee Allen, Peterson Field Guides: Edible Wild Plants of Eastern/Central North America, Houghton Mifflin Company, 1977, p. 116

Clemants, Steven; Gracie, Carol, Wildflowers in the Field and Forest, Oxford University Press, 2006, p. 76

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

9/9/2014 · Bemis Road, Pepperell, Mass­a­chu­setts
≈ 6 × 9" (16 × 23 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

8/30/2020 · Cliff Trail, Harpswell, Maine
≈ 14 × 21" (34 × 52 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

9/9/2014 · Bemis Road, Pepperell, Mass­a­chu­setts
≈ 6 × 5" (14 × 13 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

9/19/2013 · Harvard, Mass­a­chu­setts
≈ 6 × 8" (14 × 20 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

7/17/2009 · Mt. Lebanon St, Trail, Pepperell, Mass­a­chu­setts
≈ 10 × 7" (26 × 17 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

9/14/2009 · Near Nashoba Hospital, Ayer, Mass­a­chu­setts
≈ 21 × 25" (52 × 64 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

9/9/2014 · Bemis Road, Pepperell, Mass­a­chu­setts
≈ 11 × 7" (28 × 18 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

8/7/2010 · Nashua River Rail Trail, near Nashoba Hospital, Ayer, Mass­a­chu­setts
≈ 7 × 10" (16 × 25 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

8/30/2020 · Cliff Trail, Harpswell, Maine
≈ 21 × 14" (52 × 34 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

Usually pink, but may be greenish white or purple. · 8/7/2010 · Nashua River Rail Trail, near Nashoba Hospital, Ayer, Mass­a­chu­setts
≈ 4 × 4" (11 × 10 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

9/10/2016 · Arlington St., Groton, Mass­a­chu­setts

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

A bit pinker than usual. · 9/18/2010 · Nashua River Rail Trail, Groton Center, Groton, Mass­a­chu­setts
≈ 5 × 4½" (13 × 11 cm)

Persicaria persicaria (L.) Small

Persicaria puritanorum (Fernald) Soják

Persicaria maculata (Raf.) Gray

Persicaria maculosa Gray

Persicaria ruderalis (Salisb.) C.F. Reed

Persicaria ruderalis (Salisb.) C.F. Reed var. vulgaris (Webb & Moq.) C.F. Reed

Persicaria vulgaris Webb & Moq.

Polygonum dubium Stein

Polygonum fusiforme Greene

Polygonum minus auct. non Huds.

Polygonum minus Huds. var. subcontinuum (Meisn.) Fernald

Polygonum persicaria L. var. angustifolium Beckh.

Polygonum persicaria L. var. ruderale (Salisb.) Meisn.

Polygonum puritanorum Fernald

Persicaria persicaria (L.) Small

Persicaria persicaria (L.) Small nom. inval.

 

Polygonum persicaria description by Thomas H. Kent, last updated 8 Sep 2021.

© FloraFinder.org. All rights reserved.


 

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

9/10/2016 · Arlington St., Groton, Mass­a­chu­setts

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

A bit pinker than usual. · 9/18/2010 · Nashua River Rail Trail, Groton Center, Groton, Mass­a­chu­setts
≈ 6 × 9" (15 × 23 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

9/9/2014 · Bemis Road, Pepperell, Mass­a­chu­setts
≈ 6 × 8" (14 × 20 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

9/19/2013 · Harvard, Mass­a­chu­setts
≈ 8 × 6" (20 × 14 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

9/14/2009 · Near Nashoba Hospital, Ayer, Mass­a­chu­setts
≈ 16 × 24" (41 × 62 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

8/3/2009 · 111 Near 119, Pepperell, Mass­a­chu­setts
≈ 5 × 6" (13 × 15 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

9/19/2013 · Harvard, Mass­a­chu­setts
≈ 6 × 7" (14 × 16 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

8/31/2013 · Riverside Park, James River, Midlothian, Virginia
≈ 5 × 8" (13 × 19 cm) ID is uncertain

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

9/9/2014 · Bemis Road, Pepperell, Mass­a­chu­setts
≈ 6 × 8" (14 × 19 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

8/6/2009 · Nashua River Rail Trail, Groton, Mass­a­chu­setts
≈ 4 × 3" (10 × 7.7 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

8/6/2009 · Nashua River Rail Trail, Groton, Mass­a­chu­setts
≈ 5 × 3½" (12 × 9.2 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

8/7/2010 · Nashua River Rail Trail, near Nashoba Hospital, Ayer, Mass­a­chu­setts
≈ 9 × 6" (22 × 15 cm)

Polygonum persicaria (lady’s thumb, persicaria, redleg, spotted ladysthumb, Adam’s plaster, lily of the valley)

9/19/2013 · Harvard, Mass­a­chu­setts
≈ 6 × 8" (14 × 20 cm)

Range: Zones 4-8:

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