Prostrate Knotweed: Garden Gate Weed of the Month for June 2016

Summary: Garden Gate magazine calls prostrate knotweed, also known as bird-weed, low-grass and pig-weed, the weed to tame, terminate or tolerate in June 2016.

closeup of prostrate knotweed Polygonum aviculare, Reilingen municipality, Rhein-Neckar-Kreis district, northwestern Baden-Württemberg state, southwestern Germany: AnRo002, Public Domain (CC0 1.0), via Wikimedia Commons

Prostrate knotweed appears as the weed of the month to avoid tripping over and to think about controlling in the Weed Watch department of the June 2016 issue of Garden Gate magazine.

Shoots become visible after early spring rains jumpstart germination of the Polygonaceae smartweed family member’s brown-colored, curvy-topped, grainy-surfaced, triangle-shaped, 0.05- to 0.16-inch (1.2 to 4.2-millimeter) seeds. They carpet January in hardiness zone 9, February in zones 7 and 8, March in zones 5 and 6 and April in zones 3 and 4. Their fresh, intense blue-green deceives gardeners into assuming that grass is growing early because of globally warmed climate change and into neglecting earlier, easier weed-controlling measures.

Prostrate knotweed elicits sympathy as a ground cover where vegetation fears to grow and for descriptions in 1753 by Carl Linnaeus (May 23, 1707-Jan. 10, 1787).

Recognition of growth pattern and wildlife value furnish prostrate knotweed the scientific name, Polygonum aviculare (many knees [and] small birdlike), and two of four common names.

Prostrate knotweed grows jointed, long, wiry stems 3.94 to 15.75 inches (10 to 40 centimeters) upward and 3 to 4 feet (0.91 to 1.22 meters) outward. Also called bird-weed, low-grass and pig-weed, it has a stubborn taproot whose fiber-riddled sides push 10 inches (25.4 centimeters) downward into the driest, most compacted soils. It is not so anchored above ground where ribbed, rounded, sheathed, unattached stems turn football field entry points, goal mouths and hash marks into tripping hazards.

Flowers that bloom between May and November, foliage that displays red-greens before blue-greens, and fruits that emerge in July and in August join to distract passersby.

The unassuming clusters of two to eight green-colored, pink- and white-edged, 0.14- to 0.16-inch (3.5- to 4-millimeter) flowers keep up almost inconspicuous presences atop short stalks.

Magnifying glasses let through the daintiest details of delicate cymes, each of whose diminutive blooms sport five to eight stamens, three carpel-fused pistils and three styles. The alternate, hairless, 1.18- to 4.72-inch- (3- to 12-millimeter-) wide, smooth-margined, 0.39- to 1.57-inch- (1- to 4-centimeter-) long blades may be egg-, ellipse-, lance- or spoon-shaped. Flower petals and sepals need to be removed to access achenes, fruits that each encase one seed and that altogether produce 200 seeds per prostrate knotweed.

Prostrate knotweed offers not only flowering, fruiting greenery for crevices, gravel, roadsides and wastelands but also ingredients for Russian herbal medicines and Vietnamese soups and stews.

The culinary, herbal and landscape contributions prove important since deep mulching, manual weeding and shallow hoeing may work faster and longer with organic, not chemical, controls.

Core or spike aeration, lawn over-seeding and supplemental irrigation qualify as organic control measures that alter the habitat niches that dry, compacted soil-loving prostrate knotweed seeks. Prostrate knotweed resists even timely applied pre-emergent Dithiopyr, Isoxaben, Napropamide, Oryzalin, Pendimethalin, Prodiamine and Pronamide and post-emergent Bromoxynil, Carfentrazone, Chlorsulfuron, Clopyralid, Dicamba, Fluroxypyr, Metribuzin and Sulfentrazone. Weeds rarely survive past one or two years any two of the three stresses of controlled burns, herbicide treatments and severe trims in altered habitat niches.

Prostrate knotweed tends to be terminated where traffic, tripping and visibility overlap mightily and tolerated where trimming, ventilating and wilding overwhelm weeds into obeying “Sit! Stay!”

prostrate knotweed in Old World habitat, Sierra Madrona, Ciudad Real province, autonomous community of Castilla-La Mancha, south central Spain: Javier martin, Public Domain, via Wikimedia Commons

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

prostrate knotweed: AnRo002, Public Domain (CC0 1.0), via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:20131017Vogelknoeterich_Reilingen5.jpg

prostrate knotweed in habitat, Sierra Madrona, Ciudad Real province, autonomous community of Castilla-La Mancha, south central Spain: Javier martin, Public Domain, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Polygonum_aviculare_Habitus_2011-6-26_SierraMadrona.jpg

For further information:

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Available @ http://www.msuturfweeds.net/details/_/prostrate_knotweed_37

“Common Knotweed.” University of California Statewide Integrated Pest Management Program > Homes, Gardens, Landscapes, and Turf.
Available @ http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7484.html

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Available @ http://www.ipm.ucdavis.edu/PMG/WEEDS/common_knotweed.html

Johnson, Kimberly. “How to Kill Prostrate Knotweed in Lawns.” eHow > Garden > Garden & Lawn > Pests, Weeds & Problems.
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Available @ http://plantscience.psu.edu/research/centers/turf/extension/plant-id/broadleaf/prostrate-knotweed

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Available via Biodiversity Heritage Library @ https://biodiversitylibrary.org/page/358381
Available via Missouri Botanical Garden Library's Botanicus Digital Library @http://www.botanicus.org/page/358381

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Available @ http://luirig.altervista.org/flora/taxa/index1.php?scientific-name=polygonum+aviculare

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Available @ http://www.tropicos.org/Name/26000064

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Available @ http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=200006713

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Available @ http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=200006713

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