Mountain laurel (Kalmia latifolia) is flowering broadleaf evergreen shrub with a multi-stemmed growth habit. It has beautiful spring blooms, and its elliptical, glossy deep-green leaves (resembling those of rhododendrons) and gnarled stems make it attractive in all seasons. This shade-loving shrub produces clusters of rose, pink, or white flowers with purple markings in late May to early June. If the flowers are not deadheaded, nondescript brown fruits will appear, remaining on the shrub into winter. Many different cultivars are available that offer various sizes and bloom colors. Mountain laurel usually grows as a dense, rounded shrub, with branches that grow gnarlier as the shrub ages. While mountain laurel is particular about its soil needs, this plant is easy to grow in the right environment. It is a good flowering shrub for mass plantings in shady shrub borders, woodland gardens, or for foundation plantings. It partners well with rhododendrons and azaleas.
- Botanical Name: Kalmia latifolia
- Common Names: Mountain laurel, ivy bush, spoonwood, calico bush, American laurel
- Plant Type: Broadleaf evergreen shrub
- Mature Size: 5 to15 feet in height, with a similar spread
- Sun Exposure: Prefers part shade, but can tolerate full sun
- Soil Type: Thrives in cool, rich, acid soil that is moist but well-drained; does not do well in clay
- Soil pH: 5 to 5.5; like azalea and rhododendron, this is an acid-lover.
- Bloom Time: Late spring
- Flower Color: Rose, pink, white; blooms may have purple markings
- Hardiness Zones (4 to 9, USDA)
- Native Area: Woodlands in the eastern part of North America (New England south to the southern Indiana, Louisiana and the Florida panhandle)
How to Grow Mountain Laurel
Plant mountain laurel shrubs from spring after all danger of frost has passed, to summer. Plant them in soil that is cool, moist but well-drained, and acidic in pH. Space the shrubs 4 to 6 feet apart; they prefer part shade but will tolerate full sun. Avoid windy areas, if possible, especially in the northern part of the hardiness range.
Do not plant these shrubs too deeply. Make sure the shrub's crown (the point where its trunk meets its roots) is not buried. Buried crowns will suffer from rot and your shrub will likely die.
When they are young, keep the shrubs well watered, and keep the soil moist and acidic by using a layer of wood chips or evergreen bark mulch. Feed the shrubs in spring with a plant food formulated for acid-loving shrubs, such as rhododendron food.
Remove the flower clusters immediately after they have finished blooming. Pruning lightly after the blooming is finished will help keep the shrubs full and bushy.
Mountain laurel is highly prized because it performs well in part shade, but deep shade may reduce its flowering and cause leaf spots. In full sun, the deep-green leaves may turn yellowish.
These shrubs like moist but well-drained, acidic soil. Its natural habitat is woodsy areas near swampy zones, but not in soggy soil. It dislikes heavy clay soils.
Ideally, soils should be kept moist, but once established this shrub has fairly good resistance to drought, provided the soil does not overheat. To avoid allowing the roots to get soggy, planting mountain laurel in raised berms or planters can be a good idea.
Temperature and Humidity
Mountain laurel likes soil that is relatively cool, and it will do fine in the warm months provided the soil remains shaded. It normally does not like the high temperatures and dense humidity of southern coastal climates, but some cultivars are somewhat more tolerant of these conditions.
This shrub should be fed in spring with an acid fertilizer, such as that formulated for azaleas and rhododendrons. Feeding will encourage more vigorous blooming.
Mountain laurel is a slow-growing shrub that requires little pruning. Dead or broken branches can be removed anytime. Shaping pruning should be done in the spring, just after blooming is completed. Spent flower clusters should be deadheaded after the blooms fade.
Should your mountain laurel plants get too tall or gangly for your landscape design, cut them back almost to ground level to rejuvenate them. These tough shrubs can take a severe pruning when necessary. From stubs just a few inches above the ground, new foliage will arise, and your plants will mature into large shrubs once again in about ten years’ time.
Varieties of Mountain Laurel
The mountain laurel cultivars available offer various color options, including many that are bicolored. Most are 4 to 6 feet tall, but there are also several dwarfs that will reach just 3 feet in height. The European Kalmia Society provides a full list of cultivars, though these are some of the most popular choices:
- Kalmia latifolia 'Elf': This cultivar has white flowers and grows to just 3 feet tall and wide.
- Kalmia latifolia 'Minuet': This cultivar flowers with white centers speckled with cherry red markings and surrounded by cherry-red margins. It reaches a mature size of just 3 feet by 3 feet.
- Kalmia latifolia 'Olympic Fire': This shrub red-pink buds that open to dark pink flowers; it grows 10 feet tall and wide.
- Kalmia latifolia 'Peppermint': The flowers have red stripes that radiate from the flower center out to the edges of the petals, resembling hard peppermint candies. Grows 10 feet tall.
- Kalmia latifolia 'Firecracker': This cultivar tops out at 3 feet in height and has intense red-colored buds that open white then to light pink.
Toxicity of Mountain Laurel
Mountain laurel is toxic to dogs and to grazing animals, such as sheep or goats. Instances of poisoning to humans are rare, although it is reported that mild illness can result from ingesting honey made by bees that feed on the nectar of the flowers. Take care not to use the leaves of mountain laurel in place of the leaves of bay laurel, which are commonly used in recipes.
Mountain laurel is susceptible to leaf spots and blights. It is also prone to borers, scale, whiteflies, and lace bugs.
In heavy soils, mountain laurel can develop root rot, for which there is no cure.