Students for Stewardship The Cork Board
← Back to the library

Marshpepper knotweed

Persicaria hydropiper (per-sih-KAR-ee-ah hi-dro-PIE-per)

Family: Polygonaceae Non-native Herbaceous

Water-pepper is a semi-erect summer annual with a tendency to sprawl and leans on other plants for support. Its habitat includes soggy woodlands, floodplains, edges of river and ponds, roadside ditches and other poorly drained locations. Disturbed wetlands are preferred. It will grow in a variety of soil textures. In disturbed wetlands, it can spread aggressively. It is hermaphrodite, has both male and female organs, and is self-fertile. Its tiny flowers and usually bud-like in shape, not totally open. Each flower is replaced by a 3-angle, dull-looking seed. The seeds are black or dark brown. It often reseeds itself and forms colonies. Insects, Diseases, and Other Plant Problems: It has few insect problems.

Source: NC State Extension Gardener Plant Toolbox ↗ NC State Extension Gardener Plant Toolbox, 45 attributes.

How it fits the guild

Guild layer 4 - Herbaceous
See companions & conflicts ↓

Companions & Conflicts

Curated pairwise relationships between this plant and others in the library — who feeds whom, who competes, who confuses the pests. Green reads as a good pairing, red as one to avoid.

No curated interactions recorded for this species yet.

Also noted by NC State

Related species the NC State Plant Toolbox flags for this plant — look-alikes to tell apart, and plants that play a similar role in a planting. Ones we carry in the library are linked.

Full plant profile

Growing Conditions
Plant type
Edible; Herb; Weed; Wildflower
Life cycle
Annual
Light
Full sun (6 or more hours of direct sunlight a day) | Partial Shade (Direct sunlight only part of the day, 2-6 hours)
Soil texture
Clay; High Organic Matter; Loam (Silt); Sand
Soil drainage
Frequent Standing Water | Occasionally Wet
Available space
Less than 12 inches
NC region
Coastal
Growth rate
Rapid
Canopy layer
4 - Herbaceous
Form & Appearance
Habit / form
Columnar; Erect
Texture
Medium
Foliage
Deciduous
Leaf color
Green
Leaf arrangement
Alternate
Leaf shape
Lanceolate; Ovate
Leaf margin
Entire
Leaf size
3-6 inches long, < 1 inch wide
Hairs present
Yes
Leaf detail
Leaves have a strong peppery taste, often olive-green Each leaf has a short petiole.
Flower color
Green; White
Flower form
Raceme; Spike
Flower size
< 1 inch
Flower detail
Slender greenish-white nodding flower clusters having 5 sepals, 2-3 styles, 4-6 stamens, and no petals.
Bloom time
Fall; Summer
Fruit color
Brown/Copper
Fruit type
Nut
Fruit detail
Dark brown oval flattened nut.
Stem color
Green; Red/Burgundy
Stem detail
Smooth and hairless
Wildlife & Ecology
Native status
Non-native
Origin
Temp. Eurasia to Western & Central Malesia, North Western Africa
Food & Medicine
Edible parts
Leaves; Seeds; Stems
Fruit type
Nut

Edibility

Used as a spice. Leaves, seeds, and stems are edible.

Landscape Use
Landscape location
Lawn; Patio; Small Space
Landscape theme
Edible Garden; Water Garden
Design feature
Accent; Mass Planting; Small groups
Garden tags
#edible seeds #edible leaves #edible stems #colonizing #herb garden #wildflower #weedy
Problems & Resistance
Insect problems
Japanese Beetle
Propagation
Seed

Planted at Hunnicutt

Nobody’s planted this one yet.