Planteværn Online > Skadevoldere - Weed biology<br> <sub>Agro-region: Denmark</sub> - Hemp-nettle
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22.7 2019 undefined

Weed biology
Agro-region: Denmark

Hemp-nettle Previous page Next page

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Can be mistaken for

Wall Speedwell, which does not have reddish brown dots on leaf undersides.

Characteristics

Cotyledons
Broad inverted egg-shaped with entire leaf margins. Two characteristic projections at the leaf basis. Stalked. Smooth surface (stalk very hairy). Length approx. 9 mm.

True leaves
Egg-shaped with saw-toothed leaf margins. Stalked. Densely hairy surface. Length approx. 20-30 mm.

Mature plant
2 Hemp-nettle species are found in fields: large-flowered Hemp-nettle with yellow flowers and Common Hemp-nettle with red flowers. The two species cannot be distinguished at the early stages of development. Both species are vigorous plants with 30-100 cm high, erect, square stems. Below the attachments the stem is very swollen in both species. Length of flower: large-flowered Hemp-nettle approx. 20-30 mm and Common Hemp-nettle approx. 10 mm. Seed production: Common Hemp-nettle up to approx. 600 seeds per plant and Large-flowered Hemp-nettle up to approx. 450 seeds per plant.

Seed
Compressed egg-shaped with a somewhat sharp-edged periphery. The lower part of the ventral side is shaped like a round roof. The surface is slightly warty. Dark speckled. Thousand grain weight approx. 5 g.

Biology

Propagation and dispersal
Only through weeds.

Habit
Summer annual.

Importance

The Hemp-Nettle species are frequently found in both autumn- and spring-sown crops throughout Denmark. The species can be particularly frequent in humus soil or in “wet hollows” in the field. In spring-sown crops both species are an injurious weed causing quite heavy losses, even at small densities. The damage in autumn-sown crops depends on crop development during the growing season.

For treatment options, consult 'Herbicides Across'.
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Taxonomy

Labiatae.

Names in different languages

Danish : Arve, rød
German : Roter Gauchheil
English : Scarlet Pimpernel
Latin : Anagallis arvensis L.
Norwegian : Nonsblom
Swedish : Rödmire

Hemp-nettle: Very early stage
Very early stage
Hemp-nettle: Early stage
Early stage
Hemp-nettle: Leaf sheath
Leaf sheath
Hemp-nettle: Ligule
Ligule
Hemp-nettle: Top
Top
Hemp-nettle: Mature plant
Mature plant

 
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