categoryZShrubs Shrubs List 
categoryZBroadleaf Broadleaf List 
categoryZEvergreen Evergreen List 

MOUNTAIN-LAUREL

Kalmia latifolia

Heather Family [Ericaceae]

month8may month8jun month8june month8jul month8july

Berries: berryZpossible        berryZred  (poisonous, astringent)
berry8sep berry8sept berry8oct berry8nov

category
category8Shrubs
category
category8Broadleaf
category
category8Evergreen
status
statusZneophyte
flower
flower8pink
 
inner
inner8white
 
inner
inner8red
 
morph
morph8actino
 
petals
petalsZ5 petalsZ1 petalsZ10
(10)
stem
stem8round
 
toxicity
toxicityZmedium
 

June 2014, America. Photo: © Dylan Cahn
A shrub which is said to grow to 1m, but can grow much higher, perhaps 9m.


June 2014, America. Photo: © Dylan Cahn
The leaves are satin, mid-green to dark-green (pale green beneath) and elliptic. Flowers in sprays.


June 2014, America. Photo: © Dylan Cahn
Leaves mostly alternate on the twigs.


June 2014, America. Photo: © Dylan Cahn
Flowers dish-shaped, with five petals. May be pale pink or white, with deeper red markings.


June 2014, America. Photo: © Dylan Cahn
Ten long stamens with cream-coloured pollen splayed out towards the edges of the petals.


Not to be semantically confused with : Cherry Laurel (Prunus laurocerasus), Portugal Laurel (Prunus lusitanica) nor with Bay (sometimes mis-called Bay Laurel) (Laurus nobilis) [plants with similar names]

Easily mistaken for 2 other Kalmias with pinkish dish-shaped flowers :

  • Bog Laurel (Kalmia polifolia), which is more abundant than the other two rather rare Kalmias, but the leaves are mostly opposite (rather than mostly alternate for Mountain-laurel) and has smaller 10-16mm flowers (rather than 20-25mm for Mountain-laurel) and the twigs are 2-edged.
  • Sheep-laurel (Kalmia angustifolia) (which is also rather rarer than Mountain-kalmia), but the leaves are mostly opposite or whorled (rather than mostly alternate for Mountain-laurel) and has still smaller 6-12mm flowers (rather than 20-25mm for Mountain-laurel) and the twigs are round without edges.
The only other Kalmia found in the UK is the rarer Trailing Azalea (Kalmia procumbens) [R] which has star-shaped flowers, but they are still pinkish. Being an under-shrub it is much shorter at up to 25cm high.

It is an introduced species from East and North America and has naturalized in a few wet acid places in the UK (around Portsmouth, which isn't particularly noted for its mountains!).

It is toxic containing (in the leaves and berries) Grayanotoxins, mostly Grayanotoxin I (aka Andromedotoxin and Rhodotoxin), plus the glycosylated hydroquinone Arbutin. The acrid principle is AglucosideArbutin. It is poisonous to cattle, goats, deer, horses, monkeys, humans and to sheep (hence the the overall Kalmia genus name of Sheep-laurels). The symptoms of poisoning, which start after 30 minutes of ingestion, include irregular breathing, profuse salivation, runny nose and eyes, incoordination, cardiac distress, vomiting, weakness, convulsions, paralysis and coma followed by death. Anorexia and depression may also occur.

The flowers are unusual in that the anthers on the stamens are held onto the edge of the corolla (petal) by a little fold in the corolla and only released like springs when an insect touches them, perhaps to knock it temporarily unconscious!


  Kalmia latifolia  ⇐ Global Aspect ⇒ Ericaceae  

Distribution
 family8Heather family8Ericaceae

 BSBI maps
genus8Kalmia
Kalmia
(Sheep-Laurels)

MOUNTAIN-LAUREL

Kalmia latifolia

Heather Family [Ericaceae]