|Scientific Name||Polygonum lapathifolium|
|Common Names||English: Pale smartweed; German: Ampfer-Knöterich; French: Renouée à feuilles de patience|
|Description||Annual, many-formed, seed-propagated weed with spindle-shaped root.|
Hollow stem swollen above the nodes, sunken glands on the lower surface of the leaves, nodding spikes, and flattened seeds.
Slender, length three times the width, with usually reddish hypocotyls.
Erect or ascending, usually ramified, hairless, red spotted, up to 100 cm (39.37 inch) high.
Elliptical-lanceolate, widest in the lowest third, markedly petiolate, upper surface often reddish-splotched, underside heavily glandularly dotted.
Membranous tube on the leaves' bases, loosely adjacent to the stalk.
At the margin only short ciliate (magnifying glass!).
First true leaf long, narrow and hairy, with a silvery appearance.
Small, greenish white to pale pink, in erect cylindrical, terminal or axillary inflorescences. Each flower cluster grows up to 8 cm long (3.15 inch), 3 - 9 mm (0.12 - 0.35 inch) thick, nodding.
Midsummer - autumn.
Achene, about 2 mm (0.078 inch) long, flattened, dark brown, finely granular to glossy, perianth remains often attached.
Germination in late spring.
Seeds are lentiform, hard coated, shiny, black-brown.
Seed germination depth up to 4 cm (0.16 inch).
Viability of Seeds
Moist soils, disturbed sites, gravel bars, roadsides, railroads.
Particularly on nutrient-rich, friable, fresh and wet soils, often grows in irrigated fields along ditches.
P. lapathifolium is a common weed in cultivated fields, roadsides, and other disturbed areas. It is very competitive, greatly reduces yield and interferes with combine harvesting.
Useful non-chemical contribution to Integrated Weed Management
Combinations of preventive, physical and chemical control methods should be used to reduce pale smartweed development.
It is important to rotate modes of actions in order to avoid resistant weed populations.
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