WHITE HOREHOUND

Marrubium vulgare

Mint / Dead-Nettle Family [Lamiaceae]

month8jun month8june month8jul month8july month8aug month8sep month8sept

status
statusZnative
 
flower
flower8white
 
inner
inner8green
 
morph
morph8zygo
 
petals
petalsZ5
 
type
typeZtieredwhorls
 
stem
stem8angular
 
smell
smell8thyme
thyme
rarity
rarityZscarce
 
sex
sexZbisexual
 

8th June 2008, Chillerton Down, IoW. Photo: (CC by 2.0) Geoff Toone
Six groups growing; (the browner plants upper right are of course Common Nettle).


8th June 2008, Chillerton Down, IoW. Photo: (CC by 2.0) Geoff Toone
A perennial plant. Overall they are a pale green colour with downy hairs all over (apart from the petals of course).


8th June 2008, Chillerton Down, IoW. Photo: (CC by 2.0) Geoff Toone
The stems are particularly downy. They grow to 60cm high.


8th June 2008, Chillerton Down, IoW. Photo: (CC by 2.0) Geoff Toone
The plant smells of Thyme. The flowers are white and in dense multilayered whorls around the often angular stem.


8th June 2008, Chillerton Down, IoW. Photo: (CC by 2.0) Geoff Toone
The leaves are in opposite pairs arranged alternately at right-angles to each other up the stem. Leaves mealy, with blunt teeth and conspicuous raised veins underneath.


8th June 2008, Chillerton Down, IoW. Photo: (CC by 2.0) Geoff Toone
It seems that the flowers on the upper parts of each whorl are the first to shrivel up, becoming cream coloured in the process whilst those at the bottom of each whorl are the last to open (still mostly closed here). Those flowers in the centre of each whorl are open, all white, with the usual 5 petals, but the upper two are narrow and held upright nearly parallel to each other. The lowest petal has three lobes, a wide central lobe descending the furthest downwards plus two narrower and shorter 'arms' angled sideways and downwards.


8th June 2008, Chillerton Down, IoW. Photo: (CC by 2.0) Geoff Toone


8th June 2008, Chillerton Down, IoW. Photo: (CC by 2.0) Geoff Toone
In the centre are as-yet un-opened flowers, with the flower like a boxing glove visible in the centre of a multi-toothed sepal tube (calyx). The lowest flower is showing the narrow opening and some cream-coloured sexual organs within. The downy calyx has 10 teeth of equal length and which are hooked at the tip. At the fruiting stage the teeth splay outwards.


8th June 2008, Chillerton Down, IoW. Photo: (CC by 2.0) Geoff Toone
The leaves are pale-green with downy hairs, thick and mealy with several serrate blunt teeth and smell of Thyme. The upper surface is bumpy; the lower surface with very prominent veins. Lower leaves are ovate with a stalk.


No relation to : Hound's-tongue (Cynoglossum officinale) - a plant with similar name in the Boraginaceae family.

Not to be semantically confused with : Black Horehound (Ballota nigra) [a plant with similar name in the same Dead-nettle family (Lamiaceae)] but in a differing genus.

Some similarities to : Downy Woundwort (Stachys germanica) which is also in the Dead-nettle family (Lamiaceae) but in a differing genus. It too is pale-green with downy hairs but it has purple flowers which have a differing shape (they have a longish hood at the top for one thing).

Uniquely identifiable characteristics

Distinguishing Feature :

The only Marrubium species in the UK - there are many other species elsewhere. In the UK it is probably only native near the sea in the South of Britain and grows on short grasslands, or in waste places, open or rough ground. It occurs scattered sparsely in the British Isles north to Moray, becoming much rarer the further north. It is a rare [RR].


  Marrubium vulgare  ⇐ Global Aspect ⇒ Lamiaceae  

Distribution
 family8Mint / Dead-Nettle family8Lamiaceae

 BSBI maps
genus8Marrubium
Marrubium
(White Horehound)

WHITE HOREHOUND

Marrubium vulgare

Mint / Dead-Nettle Family [Lamiaceae]