Horehound

Horehound is a bushy, upright perennial herb that grows to about 50 centimetres tall. It has small white flowers that grow in tight clusters around the stem. When the flowers dry, parts can stick easily to wool and clothing.

The leaves grow in opposite pairs and are wrinkled, with a soft, downy texture, especially underneath. The small leaf like parts around the flowers have hooked tips, which can feel prickly when dry and help the plant spread.

Horehound has a very bitter taste, so animals tend to avoid eating it. It’s an issue in lucerne crops and can also invade pastures.

The plant spreads by seed, which usually germinates from autumn through to early spring when conditions are cool and moist. Most seeds remain dormant until they experience a period of cool, damp conditions. A single plant can produce up to 74,000 seeds each year.

Seeds are held in hooked structures that can stay attached to the plant for months, but easily break off when brushed by animals, livestock or people, helping the plant spread to new areas.

Horehound usually invades heavily grazed or disturbed areas and is most often found on dry, calcium rich soils. Seedlings do not compete well with other plants, so it’s mainly a problem where pasture cover is poor or damaged.

Because horehound has a bitter taste and a furry texture, stock tend to avoid eating it. This reduces access to surrounding pasture and can lower overall grazing quality. Horehound can also taint meat, and its dried seed heads can contaminate wool, reducing wool quality and value.

Horehound is rarely a problem in well managed pastures with good soil nutrients and appropriate grazing. It tends to establish on poor soils with little competition, especially during autumn.

These organisms have not been legally declared as pests but may be of interest to the public as they are commonly found.