Editing Marrubium vulgare (section)

==As an invasive weed==
Horehound was introduced to southern [[Australia]] in the 19th century as a medicinal herb.  It became a weed of native grasslands and pastures where it was introduced with settlers' livestock and was first declared under [[noxious weed]]s legislation. It now appears to have reached its full potential distribution.

In [[New Zealand]], efforts are being made to control its spread with [[Biological pest control|biocontrol]] measures using the horehound clearwing moth (''[[Chamaesphecia mysiniformis]]'') and the horehound plume moth (''[[Wheeleria spilodactylus]]''), which can eat their way through many plants.<ref>{{cite news |url=https://www.stuff.co.nz/national/112477579/moths-may-be-the-key-to-controlling-spreading-infestations-of-horehound |title=Moths may be the key to controlling spreading infestations of horehound|date=9 May 2019 |newspaper=[[Stuff (website)|Stuff]] |access-date=9 May 2019}}</ref><ref>{{cite web |url= https://www.landcareresearch.co.nz/discover-our-research/biosecurity/weed-management/approvals/horehound/ |title=Horehound |publisher=[[Manaaki Whenua – Landcare Research]] |access-date=20 June 2022}}</ref>

Horehound is usually found in disturbed and overgrazed areas. It is highly unpalatable to livestock, so livestock eat other plants around it, a process that favors the persistence and spread of the weed. It may persist in native vegetation that has been grazed.