Growing Kalmia (Mountain Laurel)
Latin Name Pronunciation: kal' mee-uh
The genus Kalmia, named after 18th-century Swedish botanist Peter Kalm, has only nine species yet is found throughout the Northern Hemisphere in regions of North America, Europe, and Japan. One species, the beloved Mountain Laurel (Kalmia latifolia), is native to the eastern United States. While Mountain Laurels thrive in part shade, they tolerate both full sun and full shade conditions including, in our experience, the north side of a two-story house. These durable shrubs shrug off cold and grow to a ripe old age in well-drained, humus-rich, acid soil. Plants require afternoon shade in the South and are ill-suited to desert conditions and alkaline soils. They should also be sited with care since all parts of the plant are toxic to people and animals if ingested.
Grow Kalmia in full sun or partial shade. (Partial shade or shade is best in the South; partial shade is recommended in the West). Mountain Laurel prefers well-drained, acid soil to which organic matter has been added. If you remove spent flower clusters as the blooms fade, you'll have a better show the following spring. Prune as needed after bloom.
Light: When grown in northern latitudes, Mountain Laurels bloom most bountifully in full sun, assuming adequate moisture. Toward the southern end of its range (Zone 7-9, depending on cultivar), provide afternoon shade to prevent leaf scald. Will grow well in deep shade but bloom more sparsely with reduced light.
Soil: Mountain Laurel requires acidic soil (pH 5.0-7.0) that is well-drained, humus-rich, and moist. It will not tolerate clay, alkalinity, or saturated soil. In its natural habitat, Mountain Laurel often grows on deciduous forest slopes, steep wetland edges, in cliffs, and in mountain meadows, all places where water flows downhill and is absorbed by the soil but doesn’t accumulate. Apply 2" of a biodegradable mulch such as Oak leaves, Pine needles, shredded hardwood, or Pine bark to moderate soil temperature, retain moisture, and replenish humus as it decomposes.
Watering: Plants have shallow root systems and appreciate watering during dry spells, especially in warmer areas and as plants are getting established. In their preferred cool, northern habitats, typical rainfall is normally sufficient except in unusually hot, dry conditions. Drought-tolerant once mature.
Fertilizing: No fertilizer is recommended, just compost applied every year or two, depending on richness of existing soil.
Pests/Diseases: Fungal leaf spots and blights can occur; adequate sun and good air circulation help control fungal diseases. Leaves and stems are poisonous. Although deer sometimes browse twigs in winter, this is not a preferred food source.
Seasonal Care: Deadheading after bloom isn’t required, but flowering will be more consistent the following season after a heavy bloom if spent flowers do not set seed. Prune lightly after blooms have faded, as needed, to enhance form. Be sure to replenish mulch and water well before the ground freezes in late fall.
