Marrubium vulgare (White Horehound)

This week’s #SxPOTW is another rarity, despite its other common name of Common Horehound. Marrubium vulgare (White Horehound) is a striking plant as can be in these wonderful photos by Polly Mair: the white ‘bunny’ flowers are instantly recognisable.

Its East Sussex stronghold is around High and Over, but it extends away from this site. It is not clear whether recent records indicate it has spread or not, so please look out for it on your walks and let us know if you see any.

The sparse distribution is clearly shown in the Flora map.

Native. Sx: scarce. Broken chalk grassland; cliff tops; coastal sand. Although considering it ‘rather rare’, W-Dod (1937) gives about 50 early locations, most of which are distributed along the Downs from Halnaker and Bignor in the west to Beachy Head in the east. Further east, there are early coastal records from the Crumbles at Eastbourne to Pevensey, Pett, Winchelsea and Rye; and in WSx there are coastal records from Sidlesham and Bognor. There are also a few records from the Weald, which are probably either casuals or on introduced chalk. Hall (1980) shows only two tetrads in WSx and five in ESx, noting that there were few plants in each site. Many of the recently recorded colonies, except for one sighting of a casual in SU70Z, are in the same areas as early records. It is obviously a persistent species, but sporadic in appearance. Numbers are variable and dependent on rabbit digging or other disturbance. In WSx it was recorded on Halnaker Hill c.1900. It was re-found there on disturbed ground in 1988 (SU90J GHF), but decreased as vegetation once again became denser. In 1999 it was discovered nearby in Halnaker Chalk Pit (HWM): a well-botanised site, but where it may have been aided by the disturbance of motorbike scrambling. No plants could be found in 2014. In the same area, there is a remarkable population of several thousand plants in fields and on dry banks and tracks near Eartham (SU90P; SU91K). The sheep-grazed fields have probably previously been cultivated, but now support thin dry chalky grassland. In Arundel Park it has been known since at least the 19th century: there are several colonies on a dry slope above Swanbourne Lake (TQ00E). Numbers vary, but in 2000 over 150 plants were present where new fencing had exposed broken chalk. It has been suggested that the place name ‘Arundel’ may derive from ‘Horehound’. In ESx it occurs on SWT’s Southerham Farm Reserve (TQ41F & K), and there are several colonies at High and Over, where ‘many hundreds’ of plants were noted on the SE slopes in 2005 (TQ51A). It has long been known on the cliff tops west of Beachy Head. Numbers increase when rabbits have been active in creating bare disturbed patches. KFR observed in 2007 that it occurred at Crowlink by a series of large collapsed burrows along a fence. There are fine populations in the Rye Harbour area, where it has long been known in sandy coastal habitats. In 2005 it was seen in quantity in ‘improved and degraded pasture’ at Rye (TQ91J AS/BJY), perhaps a similar habitat to that at Eartham.

Source: Marrubium vulgare L. White Horehound, The Flora of Sussex (2018)

The name derives from ‘hoar’, as in ‘hoar frost’, referring to the white colour. The ‘hound’ part is from ‘hune’, an old term used for medicinal plants. As far back as ancient times it was thought to be useful in treating respiratory conditions, and syrups and lozenges containing extracts from the plant have been available throughout recent times. Such was the interest in its potential that it was investigated scientifically to determine what, if any, part of the plant was useful. None, as it turned out.

In Sussex it was known as ‘Marvel’.