Kalmia latifolia

Our Botany Photo of the Day once again comes from the albums of June West, one of our Friends of the Garden. We extend our gratitude to her for yet another lovely image.

Ericaceae, commonly referred to as the heath or heather family, consists of about 100 genera and around 3000 herb, tree, dwarf shrub, and shrubby species. In general, members of the family—among them blueberry, cranberry, huckleberry, and rhododendron species—develop whorled or alternately arranged leaves and perfect (bisexual) flowers. Plants thrive in acidic soils, and most Ericaceae species form associations known as mycorrhizae, wherein specialized fungi enwrap and permeate a plants' root systems and proceed to supply them with beneficial nutrients and water. Benefits to the fungi are the carbohydrates—products of photosynthesis—supplied by the plant. This mutualistic relationship is often integral to plant survival, and is particularly so in hostile climates and habitats.

Kalmia, which receives its name from the 18th century Finnish botanist Pehr Kalm, is a small genus of 7 evergreen shrub species that are native to eastern North America and Cuba. Plants grow to a maximum height of 2.5 metres and put forth corymbs of star-shaped flowers, each of which is equipped with 5 fused petals. The fruit is a five-lobed capsule that eventually splits and disperses large numbers of small black seeds to the wind. Most parts of most plants are toxic, though some larvae of lepidopteran species, among them Coleophora kalmiella, regularly treat the plants as a source of sustenance.

Kalmia latifolia is distributed over a portion of North America that stretches from Florida to Maine and from the eastern seaboard west to Indiana and Louisiana. Plants, which thrive on rocky mountain slopes as well as in alpine forests, grow to 9 metres in height; specimens are more tree-like at low altitudes and become increasingly shrubby with elevation. In early summer, they put forth clusters of flowers that range from white to pink and red. Plants contain the toxic chemicals andromedotoxin and arbutin, and they are for that reason commonly referred to as kill-kid and sheep-poison (along with other Kalmia species).

Kalmia latifolia

14 responses to “Kalmia latifolia”

  1. Karen Newbern

    Beautiful photo – but it appears to be upside down!

  2. Mtn Laurel

    This entry made me smile the moment the e-mail popped up in my inbox, and the picture is gorgeous!

  3. Quin

    the slow ‘fireworks’ of deep pink/carmine to many tones and then lightening with age is almost too much – makes me weak in the knees – ahh, these acid-lovers…….

  4. Jennifer Frazer

    I just discovered our western version of this beautiful flower, the alpine or bog laurel — Kalmia microphylla — this summer. The little indented petal pockets for the anthers are adorable (you can see them sticking off the side in the bottom three flowers). My guidebook said that when a bee lands in the flower, the anthers automatically pop out of those little pockets to dust the insect.
    I was also amazed to find out what Kalmia was — I had lived on Kalmia Ave. in Boulder for almost a year completely unaware it was named after a flower!

  5. LJTeller

    This is one of my favorite plants, not only for the colors, but also for the “spring-loaded” action of the stamens, which stay tucked into the little cups in the petals until an unsuspecting pollinator lands in the flower and “boing!” gets slapped on the back with pollen. What an amazing modification to have evolved!

  6. chris czajkowski

    A small detail. Kalmia spp. are in the west, too. Kalmia polifolia is very common in my alpine backyard in British Columbia.

  7. elizabeth a airhart

    Down many a shelving ledge of shale
    Skirting the trembling sands
    Through many a pool&and many a pass
    Where the mountain laurel stands
    william aspinwall bradley
    1878- 1939
    brings back my i was born in the north usa memories many a drive to see the moutain laurels

  8. annie morgan

    Lovely photo, and such interesting posts.

  9. Cambree

    What a beauty! The the buds remind me of frosting.
    Too bad the “Plants contain the toxic chemicals.” But they are pretty.

  10. John Wheeler

    Greetings from the Lehigh Valley in Pennsylvania. Thank you for this beautiful photo of our State Flower – Mountain-laurel. Michael Dirr says that this is “the most beautiful flower I know”. John Wheeler – UBC Med ’57

  11. Denis

    I even tried to find Kalmia microphylla at various native plant nurseries. I have a small area of wetlands on my acreage in Columbia County, Oregon and would like to plant it, but have never found it in the nursery trade.

  12. Dana

    I do so wish I could grow this plant! But we are too hot and dry in July and August for it to survive. Perhaps when I learn more about mycorrhizae I may be able to try again.
    As to Karen that first posted on this page, the flowers are upward facing and explode right in your face just like the picture shows!

  13. Mary Ann, in Toronto

    The “spring-loaded” action of the stamens is a wonderful detail about this flower! I loved hearing about that. And it explains the shape of the flower, with the little pockets for the anthers. You can see this structure both in the open flowers, and in the flower buds. So interesting! :o)

  14. Anne

    Mountain Laurel is the Connecticut State Flower. In the spring the woods are full of them. The plant is prettiest when in flower, otherwise it’s not terribly attractive. (The flowers are also very sticky – not a scientific term, but something that seemed noteworthy when I was a child and tried to do some deadheading.)
    I rotated the picture and it’s definitely right side up!

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