Is Knot Grass Edible? A Forager's Guide to Identification and Use

January 11, 2026 •

6 min read

Knot grass, also known as prostrate knotweed or Polygonum aviculare, is a common, low-growing weed found worldwide that has been used as a food source and traditional remedy for centuries. While the young leaves and shoots are indeed edible, safe foraging requires careful identification and an understanding of its potential risks.

Quick Summary

Knot grass is edible, with young leaves and shoots suitable for consumption when properly identified. This guide covers how to distinguish it from lookalikes, best culinary uses, nutritional properties, and important safety considerations for foraging.

Key Points

Edible Parts: Young leaves, shoots, and seeds of common knot grass (Polygonum aviculare) are edible and can be eaten raw or cooked.
Safe Identification: Positive identification is essential; look for prostrate growth, wiry stems with swollen nodes, and a silvery sheath (ochrea) at the base of the leaves to distinguish it from lookalikes.
Foraging Precautions: Only harvest from areas known to be free of herbicides and pollution, as knot grass often grows in waste places where chemical treatment is common.
Oxalic Acid Content: Knot grass contains oxalic acid, and excessive consumption should be avoided, especially by individuals with kidney or joint issues. Cooking reduces the oxalic acid level.
Traditional Uses: The plant has a history in traditional medicine for its astringent and diuretic properties, used to treat diarrhea, wounds, and urinary tract issues.
Not all Knotweeds are Equal: Do not confuse common knot grass with other knotweed species, particularly the large, invasive Japanese Knotweed, which is also edible but has different growth habits and risks.
Consult a Professional: Individuals who are pregnant, breastfeeding, or have pre-existing cardiovascular or kidney conditions should consult a healthcare professional before consuming knot grass.

Introduction to Knot Grass

Knot grass, scientifically known as Polygonum aviculare, is a tough, wiry plant that is often considered a nuisance weed by gardeners. However, this resilient member of the buckwheat family (Polygonaceae) is a valuable and nutrient-rich wild edible for those who can identify it correctly. While its seeds are edible and can be ground into a flour similar to buckwheat, the young, tender aerial parts are most commonly used in cooking. Understanding its characteristics is the first step toward safely and successfully harvesting this wild green.

Identifying Edible Knot Grass (Polygonum aviculare)

To ensure you are gathering the correct plant, look for these specific features of common knot grass:

Growth Habit: It has a prostrate, low-growing form, with stems that spread along the ground rather than growing upright.
Stems: The wiry stems feature swollen nodes, giving the plant a jointed appearance, which is how it earned the name "knot grass".
Leaves: The leaves are small, elliptical to linear in shape, and arranged alternately along the stem.
Ochrea: A crucial distinguishing feature is the translucent, membranous, and silvery sheath (ochrea) that encloses the stem where each leaf is attached.
Flowers: The flowers are tiny and inconspicuous, appearing pink or greenish-white in clusters at the leaf axils from spring to autumn.

Knot Grass vs. Lookalikes: A Critical Comparison

Several plants, some poisonous, can be confused with knot grass. Proper identification is non-negotiable for safe foraging. For instance, Japanese Knotweed (Fallopia japonica) is a larger, invasive plant that, while edible when young, is a destructive species with different characteristics. Giant Hogweed is also a lookalike and is highly toxic, causing severe skin burns.


Feature	Common Knot Grass (P. aviculare)	Japanese Knotweed (F. japonica)	Giant Hogweed (H. mantegazzianum)
Growth Habit	Prostrate, low to the ground	Tall, upright, resembling bamboo	Very tall, can reach over 10 feet
Stems	Thin, wiry, jointed	Thick, hollow, red-speckled	Thick, hollow, with purple splotches
Leaves	Small, narrow, elliptical	Large, broad, spade-shaped	Very large, deeply lobed
Ochrea	Present, silvery, membranous	Present, but different texture	No ochrea present
Flowers	Tiny, pinkish or whitish clusters	Lacy white clusters in late summer	Large, umbrella-shaped white clusters
Risk	Safe for moderate consumption	Edible when young, but invasive	Highly toxic, causes severe burns

Potential Health Benefits and Risks

Beyond its culinary use, knot grass has a long history in traditional medicine, particularly for its diuretic and astringent properties. The plant contains several beneficial compounds, including flavonoids, tannins, and vitamin C, which are known for their antioxidant and anti-inflammatory effects.

However, there are important health considerations to keep in mind:

Oxalic Acid: Knot grass contains oxalic acid, which can interfere with the body's absorption of certain minerals. Cooking the plant significantly reduces this content.
Pre-existing Conditions: Individuals with a history of rheumatism, gout, arthritis, kidney stones, or hyperacidity should use extra caution or avoid consumption entirely, as oxalic acid can aggravate these conditions.
Contraindications: Pregnant and breastfeeding individuals should avoid knot grass due to insufficient safety information. Certain herbal preparations of knot grass are also not recommended for those with specific cardiovascular issues.
Source Contamination: Forage only from areas you know are free from herbicides, pesticides, and other pollutants. As a resilient weed, knot grass often grows in waste places and roadsides, where chemical treatment is common.

Culinary Uses of Knot Grass

Knot grass is a surprisingly versatile ingredient, with a taste profile that can vary depending on the preparation. Here are some of the ways you can use it:

Fresh in Salads: The young, tender leaves can be added to salads for a fresh, slightly tangy flavor. A classic preparation, especially in Lebanese cuisine, is to chop the aerial parts and mix them with tomatoes, oil, and vinegar.
Cooked in Soups and Stews: Like many other wild greens, the leaves and young shoots can be cooked as a potherb, added to soups, or sautéed. This also helps reduce the oxalic acid content.
Ground Seeds: The seeds, although small and fiddly, can be harvested and ground into a flour. This flour can be used as a substitute for buckwheat in recipes like pancakes and biscuits.
Herbal Tea: The leaves can be dried and steeped to make a tea.

Foraging for Knot Grass Safely

Foraging can be a rewarding experience, but safety must always be the top priority. Here are some essential guidelines for harvesting knot grass:

Positive Identification: Always be 100% certain of your identification. Use multiple reliable sources to confirm the plant's features before harvesting.
Forage Cleanly: Never harvest from roadsides, industrial sites, or areas where herbicides or pesticides may have been used. Avoid plants that look discolored or unhealthy.
Harvest Young Growth: The stems and leaves become tough and stringy as the plant matures. Harvest the youngest, most tender parts in spring and early summer for the best flavor and texture.
Leave Some Behind: Never strip a patch of all its growth. Leave plenty of plants to ensure the species can continue to thrive and reproduce.
Wash Thoroughly: Always wash harvested plants thoroughly to remove any soil, debris, or contaminants.

Conclusion

Yes, knot grass is edible, and its long history of traditional use as both a food and a medicine speaks to its versatility. When properly identified and prepared, it can be a nutritious and flavorful addition to your meals, much like other wild greens. However, responsible foraging and an awareness of the potential risks, particularly for those with certain health conditions, are essential. By following clear identification rules and sticking to safe harvesting practices, you can enjoy the unique flavor and benefits of this resilient wild edible. For additional information on specific medicinal uses, consult an expert or refer to reputable sources such as the European Medicines Agency's findings on knotgrass herb.

Disclaimer: This article is for informational purposes only. It is not intended to provide medical advice. Before consuming any wild plant, consult a healthcare professional, especially if you have pre-existing health conditions or are pregnant or breastfeeding.

Knot Grass vs. Other Common Greens: A Nutritional Overview

While knot grass offers unique benefits, it's helpful to see how it compares to more familiar greens. While precise nutritional data can vary, this table offers a general comparison based on known properties and traditional use.


Attribute	Knot Grass (young)	Spinach	Rhubarb (stem)
Key Nutrients	Vitamin C, flavonoids, tannins, minerals (zinc)	Vitamin K, Vitamin A, Vitamin C, Iron, Folate	Vitamin C, Vitamin K, Fiber, Calcium
Flavor Profile	Mild, slightly astringent, some compare to rhubarb	Mild, earthy	Tangy, sour (often sweetened)
Oxalic Acid	Present; reduced by cooking	High; reduced by cooking	High; should be cooked
Culinary Uses	Salads, soups, cooked green	Salads, cooked dishes, smoothies	Pies, crumbles, sauces
Foraging Risk	Low-moderate (requires identification)	None (cultivated)	Low-moderate (leaf is toxic)

Knot Grass in Traditional and Modern Contexts

From ancient folk medicine to modern herbal supplements, knot grass has a history as a valued plant. In traditional settings, it was used to treat various ailments, from wounds and diarrhea to respiratory issues. Its astringent properties were used to staunch bleeding, and its diuretic effects were prized for supporting urinary tract health. Modern research has continued to investigate its potential, with studies confirming strong antioxidant and anti-inflammatory properties, though more human clinical trials are needed. The growing interest in herbal medicine and wild edibles has brought this resilient plant back into the spotlight, reminding us that valuable resources can often be found close to home, provided we approach them with knowledge and caution.

Responsible Harvesting and Preparation

To minimize health risks associated with knot grass, especially the presence of oxalic acid, always opt for young leaves and shoots. For those with sensitivities, cooking is the recommended method of preparation over consuming raw. Blanching and discarding the cooking water can further reduce the oxalic acid content. When making an infusion or tea, use only the recommended dose and consult a professional, as some preparations can have potent effects.

By following these guidelines, enthusiasts can safely incorporate knot grass into their diet and explore the benefits of this unassuming yet valuable plant. As with any wild edible, respect for the plant and its environment is key to a sustainable foraging practice.

Frequently Asked Questions

The young leaves, tender shoots, and seeds of common knot grass (Polygonum aviculare) are edible. The seeds can be ground into a flour, while the young leaves and shoots are added to salads or cooked.

Yes, knot grass has been traditionally used for its medicinal properties and contains beneficial compounds like flavonoids, tannins, and Vitamin C. It is known for its diuretic and astringent effects and has shown antioxidant and anti-inflammatory activity in studies.

Knot grass is generally considered safe in moderate amounts, but it contains oxalic acid, which can be problematic in large quantities for people with conditions like rheumatism, gout, or kidney stones. It is also crucial to avoid foraging from chemically treated areas.

Common knot grass (P. aviculare) is a small, low-lying plant with wiry stems and an enclosing silvery sheath (ochrea) at the nodes. Japanese Knotweed (Fallopia japonica) is a much larger, tall, and invasive plant with thick, bamboo-like stems and broad leaves.

You can eat young knot grass leaves raw in moderation. However, cooking it is recommended, as this reduces the oxalic acid content, which can be beneficial for those with sensitivities.

Yes, knot grass is contraindicated during pregnancy and breastfeeding due to a lack of sufficient safety data. Individuals with cardiovascular conditions, a tendency for blood clotting, or kidney stones should also avoid it or consult a doctor first.

Forage for knot grass in wild areas far from roads, industrial sites, and conventional gardens where it may have been sprayed with herbicides. Always choose healthy-looking plants from a clean environment.

The flavor of knot grass is often described as mildly astringent and slightly tangy. Some people find it has a flavor reminiscent of rhubarb, particularly when cooked.