Polygonum lapathifolium

Scientific Name Polygonum lapathifolium
Synonyms Persicaria lapathifolia
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.

Descriptions

Characteristic Features

Hollow stem swollen above the nodes, sunken glands on the lower surface of the leaves, nodding spikes, and flattened seeds.

Cotyledons

Slender, length three times the width, with usually reddish hypocotyls.

Stems

Erect or ascending, usually ramified, hairless, red spotted, up to 100 cm (39.37 inch) high.

Leaves

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.

Propagatio Organs

Flowers

Small, greenish white to pale pink, in erect cylindrical, terminal or axillary inflorescences. Each flower cluster to 8 cm long (tall) (3.15 inch), 3-9 mm (0.12 - 0.35 inch) thick, nodding.

Flowering Period

Midsummer - autumn.

Fruit

Achene, about 2 mm (0.078 inch) long, flattened, dark brown, finely granular to glossy, perianth remains often attached.

Seeds

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

10-13 years.

Propagation

By seed.
800-850 seeds/plant.

Occurrence

Habitat

Moist soils, disturbed sites, gravel bars, roadsides, railroads.

Soil

Particularly on nutrient-rich, friable, fresh and wet soils, often grows in irrigated fields along ditches.

Agricultural Importance

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.

Control

Integrated Crop Management

Combinations of preventive, physical and chemical control methods should be used to reduce Pale smartweed.

Chemical Control

It is important to use herbicides with different modes of actions in order to avoid resistant weed populations.

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