Polygonaceae – Buckwheat
Comprising about 30 genera and 1,000 species, members of the Polygonaceae produce some well-known foods including buckwheat (Fagopyrum spp) and rhubarb (Rheum rhabarbarum), as well as some of North Americas most problematic invasive weeds – including species of Persicaria,[1] Rumex (ex. sheep’s sorrel), and Polygonum (ex. Japanese knotweed).[2]
Stems have swollen nodes with sheathing stipules (a papery membrane structure associated with petioles or nodes) called ocreas.[3] These sheathed ocreas give this family its name, where “Polygonaceae” broken down, “Poly” and “Genu,” in Latin translates to “many knees” in English referring to the nodes.[4] In our area, members of the Buckwheat family are annual and perennial herbs with simple leaves that are basal or alternate and cauline (emerge from the stem).[5]
Flowers are very small and radially symmetrical (actinomorphic), lacking petals, these plants have three to six connate sepals, with four to nine stamens arranged in two whorls.[6] The superior ovary consists of three united carpels that mature into a three angled/three winged dry achene that is wind dispersed.[7]
Rumex salicifolius var. salicifolius – Willow Dock
Species Code: RUSA
Habit: Leafy, clustered plant with erect open panicles.
Leaves: Alternately arranged, cauline leaves are 3 to 20 cm long with a short petiole. Leaf blades are linear to lanceolate with entire margins that can be flat or wavy. Leaves emerge oppositely from sheaths at swollen nodes along the stem.[8]
Stems: Long, slender stalks begin as semi-decumbent (growing along the ground) and develop into erect stems reaching almost 90 centimeters in height. Stems produce axillary shoots below 1st-order inflorescences or at nodes near the center of the plant.[9]
Flowers: Inflorescence made up of a bracted cluster arrayed in several erect terminal panicles. Inflorescence panicles are 15 to 30 cm long, covered in dense bunches of many small greenish flowers.[10] Flowers have six persistent perianth lobes – outer three are inconspicuous, inner three are hardened, covering the fruit; Inner perianth lobes are 2 to 3 mm long, narrowly ovate to round, six stamens and three fringed stigmas.[11]
Fruits: Seeds are shiny, brown and round, generally 1.5 to 3 mm long.
Ecology: Facultative Wetland Species (FACW), a Hydrophyte that occurs mostly in sites that are wet in spring but dry by late summer and tolerates dryer areas.[12]
Notes: May be confused with the leaves of Curly dock (Rumex crispus), a related but invasive species from the Eastern Hemisphere. Rumex crispus has a red stalk with wider leaves than those of Willow Dock, with very wavy margins that turn brownish/red when dry.[13]
Polygonum douglasii – Douglas knotweed
[1] USDA Plants Database: <https://plants.usda.gov/core/profile?symbol=POCEL>
[2] Peter Del Tredici, Wild Urban Plants of the Northeast, a Field Guide. Cornell University Press, NY. 2008.
[3] Pell, Susan. A Botanist’s Vocabulary. Timber Press, Portland, OR, 2016. 195
[4] Simpson, M. Plant Systematics 2nd ed. Academic Press, Burlington, MA. 2010. 309
[5] Gilkey, H. Handbook of Northwestern Plants, Revised Edition. Oregon State University Press; Corvallis, OR. 2001. 115
[6] Gilkey, H. Handbook of Northwestern Plants, Revised Edition. Oregon State University Press; Corvallis, OR. 2001. 115
[7] Elpel, T. J., Botany in a Day: The Patterns Method of Plant Identification. HOPS Press, 2004. 65.
[8] Gilkey, H. Handbook of Northwestern Plants, Revised Edition. Oregon State University Press; Corvallis, OR. 2001. 115
[9] Guard, J. (1995). Wetland Plants of Oregon and Washington. Lone Pine Publishing, Edmonton, Alberta. 104.
[10] Gilkey, H. Handbook of Northwestern Plants, Revised Edition. Oregon State University Press; Corvallis, OR. 2001.
[11] Gilkey, H. Handbook of Northwestern Plants, Revised Edition. Oregon State University Press; Corvallis, OR. 2001.
[12] USDA Plants Database: <https://plants.usda.gov/core/profile?symbol=RUSA>
[13] Peter Del Tredici, Wild Urban Plants of the Northeast, a Field Guide. Cornell University Press, NY. 2008.
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