Persicaria glabra: Denseflower knotweed

Family: Polygonaceae
Common name: Denseflower knotweed, Common marsh buckwheat, Smooth smartweed, Polygonum glabrum, Persicaria densiflora

Seen very commonly near lakes and rivers, Denseflower knotweed plants are distinguished by their pink and red long inflorescence. These plants are erect annuals or perennials that can grow to a height of 1-1.5 meters.

The stem is distinctly red and swollen at the nodes with ring-like markings. Leaves are waxy, narrow, smooth, and lance-like, about 20-22 cms long. Ochrea or the sheath that covers the stem near the nodes is clearly visible near stem nodes.

Inflorescences are tall racemes with many pinkish-white flowers along a red central stalk. Flowers are very pretty with 5 sepals, petals, as well as stamens and style prominently visible. They also produce fruits that are brown-black, glossy, and ovoid about 2mm long.

Denseflower knotweeds are almost completely eciliate or hairless, but they have oil glands along the lower surface of the leaves. Flowering and fruiting take place from October to March.

As the name suggests, these plants love growing in marshy areas very close to lakes, ditches, rivers, or other low-lying areas. They are seen in tropical countries like India, Malaysia, Pakistan, Bangladesh, Srilanka, the Philippines, etc.

Studies have shown that Denseflower knotweed plants have some antimicrobial properties again bacterial strains like gram-positive and gram-negative bacteriae. They have been used in the treatment of pneumonia, jaundice, colic, and fever.

Propagation is through seeds and stem cuttings, which are capable of rooting at the nodes.