Yes, it is widely considered a weed because it grows aggressively in disturbed areas.

Young leaves are edible, but they are often bitter and contain oxalates.

Plant guide

Prostrate knotweed.

Polygonum aviculare

Pronounced po-LIG-o-num a-vik-yoo-LAIR-ee

Also known as English knotgrass, Knotgrass, Knotgrass agg., Knotweed, Prostrate knotweed, doorweed

Prostrate knotweed is a tough, low growing plant that often shows up in compacted soil or along paths. It forms dense mats that can handle quite a bit of foot traffic. You will likely see it popping up in cracks in the sidewalk or in neglected garden beds.

Another photo of prostrate knotweed — Photo by Douglas Goldman (CC BY-SA) via iNaturalist

At a glance

Care level: Easy
Plant type: Annual herb
Light: Full sun
Indoor light: Direct sun
Water: Every 7 to 14 days
Mature size: Up to 20 inches tall (usually much lower when trampled)
Growth rate: Fast
Hardiness: USDA 3 to 9
Bloom time: Late spring to early autumn

Care

This plant is incredibly resilient and rarely needs any special attention. If you want to keep it in check, just pull it by hand before it goes to seed. Watch for it spreading into areas where you prefer a different ground cover.

Watering: It is quite drought tolerant once established.
Feeding: It does not require any supplemental fertilizer.
Pruning: Trim back if it starts to spread into unwanted areas.
Repotting: This plant is typically not grown in containers.
Soil: Compacted or poor soil
Soil pH: Neutral to alkaline
Temperature: -20 to 35°C
Humidity: 30 to 70%

Safety

People: The plant is generally considered safe but contains oxalic acid, which can be problematic for people with kidney issues.
Children: The plant is not toxic, but small children should be discouraged from eating wild plants to avoid accidental ingestion of contaminated soil.
Contact allergens: The stems can be slightly rough, but there is no significant contact dermatitis risk.
Airborne allergens: Pollen may cause mild seasonal allergies in sensitive individuals.
Edibility: While young leaves are sometimes eaten, they contain oxalates and should be consumed in moderation.

How to identify it

low growing mat forming habit
small lance shaped blue green leaves
tiny white or pinkish flowers
swollen stem nodes
wiry stems branching from base

Height: 0.05 to 0.5m
Spread: 0.1 to 0.6m
Leaves: green, blue-green, deciduous
Flowers: white, pink, green, 0.2 to 0.4cm
Fruit: brown, black, Late summer to autumn

Problems to watch for

Powdery mildew · A white fungal growth on leaves caused by poor air circulation.

By symptom

Plant problems by symptom

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Growing it

Propagation: seed
When to plant: spring, autumn

This plant is best suited for wild areas where you do not mind aggressive spreaders.

Grows well with

Common Yarrow · They share similar soil preferences and drought tolerance.

Similar species

Prostrate Knotweed · It is very similar in appearance and often confused with common knotweed.

Science

Family: Polygonaceae
Genus: Polygonum
Order: Caryophyllales
Class: Magnoliopsida
Native range: Europe and Asia, though now naturalized globally.
Conservation: It is a common, widespread weed and is not of conservation concern.

It thrives in disturbed, compacted soils where few other plants can establish.

Value to wildlife: nectar source, seed source for birds
Pollinators: bees, butterflies
Uses: ground cover, forage, traditional herbal tea

Through the year

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Flowering

Fruiting

Foliage

Ecological indicators

Salinity: 3/9
Soil reaction: 6/9
Light: 7/9
Temperature: 5/9
Moisture: 4/9
Nutrients: 5/9

Taxonomy resolved against GBIF.

Questions people ask

Is it a weed?: Yes, it is widely considered a weed because it grows aggressively in disturbed areas.
Can I eat it?: Young leaves are edible, but they are often bitter and contain oxalates.

Where the name comes from

The name Polygonum comes from Greek for many knees, referring to the swollen stem nodes, while aviculare means little bird, as birds love the seeds.

Good to know

It is often called knotgrass because of the swollen joints on its stems.
The plant has a deep taproot that helps it survive in compacted, dry soils.
It is a cosmopolitan species found on almost every continent.

Keep your prostrate knotweed growing

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This guide was generated with AI on October 19, 2026 and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.