Thursday, July 27, 2023

Plant profile: Jumpseed

Persicaria virginiana, formerly Polygonum virginianum, Antenoron virginianum, Tovara virginiana


Jumpseed, also called Virginia knotweed or woodland knotweed, is a perennial herbaceous plant native to the eastern U.S., including southeast and east central Minnesota. It thrives in the damp soils and part shade of deciduous woods and edges, often where there has been some disturbance. These plants were growing along a trail through a woodland.

From July into September, the plants produce long, slender racemes bearing tiny, whitish flowers, each just a few millimeters across when fully open. After pollination by honeybees, bumble bees, leaf-cutting bees, and other bees and wasps, the flowers form small fruits that are deflexed – they angle downward on their short pedicels (flower stalks), a tensioned position that needs only a slight touch to be released. When it is, the fruits “jump” off the plant. Their hooked ends, formed by remnants of their styles, can latch on to fur or clothing and help the seeds travel farther from their parents.

Jumpseed flowers in mid to late summer, producing slender racemes up to 16 inches (40 cm) long. The small flowers
have four sepals, but no petals. Fruits have hooked tips that can latch on to passing animals, including humans. 

Jumpseed also spreads by rhizomes, underground stems that form patches of plants. Where the plants aren’t desired, this can be a problem, because they tend to persist even after pulling. The same is true for eastern jumpseed, an introduced plant. Once considered a variety P. virginiana called filiformis but now recognized as a separate species, Persicaria filiformis, it is beginning to develop a reputation as invasive because of its rhizomatous habit. It differs from P. virginiana in having pink to red flowers and often variegated leaves, characteristics that make it popular in the horticultural trade. Several cultivars of eastern jumpseed, such as ‘Painter’s Palette,’ ‘Lance Corporal,' and ‘Batwings,’ are offered for sale from some nurseries.

The last two cultivar names come from colorations on jumpseed’s leaves. In spring, the leaves are marked with maroon or dark green chevrons, upside down V’s that resemble military insignia or wings. The chevrons on Virginia jumpseed disappear by the time the plants flower, but those on eastern jumpseed leaves may persist.

Jumpseed has alternate leaves and hairy ocreas.
Notice the swollen nodes. 
Jumpseeds belong to the buckwheat or knotweed family, Polygonaceae (poly-gon-AY-see-ee). A typical trait of the family is a thin sheath called an ocrea (or ochrea) above each node. In formal terms, the sheath is described as scarious, meaning it is dry and membranous. The ocrea is formed from stipules that, sometime in the long history of knotweeds, fused to form a tube around the stem. 

Another trait that identifies this family is its knobby or swollen nodes. They resemble knees, if you use your imagination. Polygonaceae means “many knees.”


Maryland Invasive Species Council (Persicaria filiformis)

John Philip Baumgardt. How to Identify Flowering Plant Families: A Practical Guide for Horticulturists and Plant Lovers. Timber Press, 1982. 

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