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Plants of the Eloise Butler Wildflower Garden
The oldest public wildflower garden in the United States

Common
Name

Scientific
Name

Plant
Family

Garden
Location

Prime
Season

Arrow-leaved Tearthumb

Persicaria sagittata (L.) H. Gross

Former Polygonum sagittatum L.

Buckwheat (Polygonaceae)
Woodland
Late Summer to Autumn
Other names and notes

Tearthumbs are native weak-stemmed plants that sprawl in moist areas. In the Arrow-leaved Tearthumb, a native annual, the stems grow from 3 to 6 feet long by climbing on and over other vegetation. There are no tendrils or twining stems. Stems are 4-angled, hollow, green to pinkish red when in full sun. Stem joints are swollen at the nodes. The leaves are alternate, entire, arrow shaped with downward pointing lobes that surround the stem with a heart shape base. An ocrea forms at the stem where the leaf joins but is only on the side opposite the leaf joint. (Ocreas are small sheaths the wrap the stem - replacing stipules that would normally be that position - common in grasses). The jointed stems and the leaf midrib underside are covered with tiny backward pointing (retrorse) prickles, giving the common name "tearthumb", which happens if you run your fingers up the stem. The inflorescence consists of tight uninterrupted flower clusters on long stalks, either terminal or from the leaf axils. Cluster stalks may but normally do not have prickles. The flowers are small, 3/8" long, and perfect, with either white or pinkish 5-parted corolla lobes. The petals and sepals of the calyx are combined as tepals, each subtended by a small green bract. Flowers usually have 8 stamens with white filaments and white to pinkish anthers. Three styles appress together in their middles forming a column. Seed: Fertile flowers produce a dry achene that is somewhat 3-sided, smooth surfaced and varying in color from light brown to black.

Habitat: Arrow-leaved Tearthumb is an annual with a fibrous root system, growing each year by reseeding. The plant grows in moist areas that have lots of sunlight such as marsh edges, damp roadside ditches, shorelines, etc. Names: Botanists have recently reclassified a number of species from Polygonum to the genus Persicaria, which is a medieval name for Knotweeds. The older genus name Polygonum is from the Greek polygonon, which is derived from polys, meaning 'many or much' and then from either gonos, meaning 'seed' or from gony meaning 'knee-joint'. So the word has two possible meanings - many seeds, which the genus tends to have - or referring to the jointed stems on plants of this genus. The species sagittata or sagittatum is Latin for the arrow shape of the leaf. Many references will still classify this species in the Polygonum genus. The plant author name 'L.' is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. ‘H.Gross’ is for Hugo Gross (1888-1951) French botanist. Comparisons: While there are 12 different species of Persicaria in Minnesota, none have the characteristics of this plant, particularly the retrorse prickles.

Arrowleaf Tearthumb
Arrowleaf Tearthumb
Above left: Both the terminal flower cluster and a leaf axil cluster are visible. Above right: The leaf structure from which comes the name "Arrow-leaved". Below left: The backward pointing stem prickles from which comes the name "tearthumb". Below right: Flower cluster detail showing one open 5-lobed flower.
Arrowleaf Tearthumb
Arrowleaf tearthumb
Arrowleaf Tearthumb flower cluster
Arrowleaf tearthumb flower cluster
 
plant image  

Notes: Arrow-leaved Tearthumb is indigenous to the Garden; Eloise Butler catalogued it on Sept. 6, 1907. Martha Crone's 1951 inventory of plants in the Garden at that time included it. It is native to Minnesota in wooded counties of the state, roughly those east of a diagonal running from Mower in the south to Marshall in the Northwest. In the U.S. it is found from the great plains east to the coast. In Canada from Manitoba eastward to the coast. There are 12 species of Persicaria found in Minnesota, all but two are found in Hennepin County.

Uses: It is not known that the plant was ever used for any purpose in North American but Mrs. Grieve (Ref.#7) reports that when it made it way to Europe the Irish are said to have used the plant to treat kidney pain and abdominal pains.

 
 

 
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applies. Distribution principally from Wi, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.  
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