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Horehound

Horehound2

Horehound1

Horehound3

Salvia verb1

Salvia verb2

Salvia verb3

Salvia verb4

Mintweed plant

Mintweed seed capsules

Plectranthus graveolens

Plectranthus graveolens flowers

Plectranthus graveolens leaves



BOTANICAL NAME:

Marrubium vulgare


Family:

Lamiaceae (mints)

Status:

Horehound is declared noxious in the Southern Tablelands and South East Region in Bombala, Cooma-Monaro, Palerang, Snowy River and Southern Slopes LCAs in class 4.

Description

Bushy perennial aromatic herb to about 30cm high. Near-circular opposite grey-green leaves are velvety and wrinkled with toothed edges. Small white flowers are carried in dense clusters in the axils of the upper leaves. Fruits are tubular burrs each with up to 4 seeds.

preferred habitat and impacts


Horehound prefers full sun and disturbed ground on grazing land, roadsides or waste ground. Old rabbit warrens and sheep camps are the most likely sites of invasion. It tolerates drought and poor soils and spreads when overgrazing or drought removes more palatable species. It is not very palatable to stock but taints meat if grazed.

Dispersal

Burrs attach to animals, clothing, car tyres and machinery or are spread in mud, soil and water and in animal dung.

Look-alikes

The related wild sage (Salvia verbenaca) is another common aromatic weed with a less bushy habit. Its leaves are oval and more deeply toothed, less woolly and on longer stalks. Flowers are blue-purple in terminal spikes. Mintweed (Salvia reflexa) is a taller plant to about 60cm high with opposite grey, hairy leaves which are narrower than those of horehound and only slightly toothed. They have a minty smell when crushed. It has very pale blue flowers in opposite pairs or clusters of 3 or 4 at the branch tips. These are followed by papery, tubular brown seed capsules.  It can be very invasive in wet areas such as creek flats on heavy clay soils.  It is poisonous to stock, containing nitrates. Although it is not yet listed as noxious in the region, it is a significant weed and you should notify your local Council weed officers if you think you have seen it.  On the coast (where horehound is uncommon) there is a slightly similar native plant, blue cockspur flower (Plectranthus parviflorus and P. graveolens). The latter species particularly, has thick, felty leaves, but they are usually more widely spaced along the stems and the flowers are small and blue, and held in elongated terminal spikes, not in the leaf axils. In tends to grow on rocky sites.

Control

Chip, spot spray, or boom spray larger infestations prior to seeding or burn plants after chipping or spraying if seed is present. Fire will stimulate germination of most seed for further treatment. Vigorous pasture is unlikely to be invaded so avoid creating bare ground.