Mountain laurel, calico-bush, spoonwood

Kalmia latifolia is one of eight species from the mountain laurel genus. The evergreen shrubs are native to Eastern North America, from New Brunswick to Ohio, Tennessee, Florida and Louisiana. There, they grow on open, dry slopes, as well as in moist, light forests. It is the ‘state flower’ of Pennsylvania. The botanical name of the genus "Kalmia" can be traced back to the Swedish botanist Peter Kalm.

The mountain laurel develops into a dense, bushy shrub. It reaches a height of a little over 6.6 feet and is equally as wide. It grows somewhat taller in its native home. Growing at a rate of 3.94 to 7.87 inches, Kalmia latifolia is a decidedly slow grower. Mountain laurel has a very similar appearance to rhododendrons and azaleas, but it is overall more easy-care. The even structure of the shrub becomes increasingly loose with age, it can even develop into a small tree with a bizarre habitus. It has flat roots.

The leaves of the mountain laurel are opposite one another, oval-lanceolate to elliptical-lanceolate shaped and grow up to 4.72 inches long. They shine dark green and become somewhat lighter over time.

Large, 3.15 to 3.94 inch wide, glandular hairy corymbs appear on the shoots between May and June. The leaves are slightly sticky on the outside, cup or bowl shaped and roughly 3.94 inches wide. Their color varies from white to pale and dark pink. The buds are are conspicuously wrinkled and a much darker green color than the flowers.

The pollination mechanism is a particularly special feature: The five petals have ‘sacks’ which curve outwards. The stamens remain inside these until the are mature, the filaments are tensioned. They release their pollen when stimulated by touch - such as from an insect.

The capsule fruit consists of five follicles. The winged seeds are barely 0.04 inches big.

Kalmia latifolia prefers sun to semi-shade. The sunnier the place, the better the water supply should be. The frost-hardy shrub likes it cool and humid, protected from the wind, late frost and strong afternoon sun.

Mountain laurel grows well in fresh, moist and even wet soils. Always ensure there is drainage. The non-calciferous shrub likes strongly acidic to neutral soil, it is also a fan of humus.

Mountain laurel can be planted in September or in the spring. Heavy, waterlogged soils should be well loosened and mixed with coarse sand and fine gravel. As mountain laurel prefers moist, humus-rich soils, plenty of humus can be mixed in directly when planting.

It is recommended to add compost or organic fertilizer, for example, horn shavings, in the spring. It should be regularly watered with lime-free (rain) water during lasting periods of dryness. During the flowering period, deadhead wilting flowers to stimulate continued flower formation. A mulch layer keeps the soil moist, particularly in the winter. Avoid hoeing due to the flat reaching roots. Young plants in particular are thankful for wind protection. Container plants should be well wrapped in fleece, film or jute and the pot placed on little feet. Note: When working with poisonous plants, it is recommended to wear not only gloves, but also eye and mouth protection.

Pruning is generally superfluous for mountain laurel due to its slow growth. Only dried, criss-crossed or inward growing twigs and branches should be regularly removed.

Similarly to rhododendrons, Kalmia latifolia is most impressive in the semi-shade of large trees, in the sun (provided there is a good water supply), or as a solitary plant. Mountain laurel is a wonderful supplement to simultaneously flowering azaleas and rhododendrons. Older shrubs which are becoming bare lower down can be under-planted with coral bells or other shrubs with colorful foliage. It can also be readily cultivated in containers. Spoons were previously manufactured from the wood. Note: All plant parts are poisonous, including for dogs, cats and horses. Symptoms include nausea, dizziness and paralysis of cardiac and respiratory function.

The number of varieties is continually growing; the differences are mainly in the flower colors, markings, sizes and number, however all representatives are decorative and flower intensively. The varieties are generally significantly smaller than the wild types, they usually only grow to a height of 3.28 feet. ‘Ostbo Red’ is a well known American variety with red, glowing buds which later fade to light pink. The long flowering period is notable. ‘Sarah’ is considered a wonderful, saturated pink variety which flowers over moss-green leaves. The flowers of ‘Clementine Churchill’ are Titian red on the outside and dark pink inside. ‘Peppermint’ fascinates with red stripes on a white background, ‘Vanilla Creme’ captivates in brilliant white with pink markings on the calyx, ‘Nani’ is white with a blackberry colored margin. Just take a look around: Collecting mountain laurels can become addictive!

The light germinators propagate well through seed sowing. However, it takes at least five years for the first flowers to appear. Use cuttings for pure variety propagation, you can also try layering, although the growth rate is minimal. The variety of mountain laurels in garden centers has grown dramatically since it has become possible to successfully reproduce Kalmia latifolia through micro-propagation.

Pests are not very interested in mountain laurel, feeding damage can indicate taxus weevils, if this occurs on the roots it can kill Kalmia latifolia. Leaf margin necrosis can be caused by salt damage or over-fertilizing. Leaf spot diseases only lead to an unpleasant appearance.