Almost every garden has shade, and so plants that grow well without direct sun are always in demand. When they are attractive evergreen shrubs, with gorgeous flowers carried over a long season, they are even more desirable. Finally reaching a wider gardening audience, the Mountain Laurel, or Kalmia, is such a plant, which blooms spectacularly in the weeks between spring and summer. It has been improved by the dedicated work of just a few plant breeders, so that now we have access to a wide range of sizes, flower forms and colors, and this great plant can take its rightful place in our gardens. Although it has some need for acid soil, it is less demanding than Rhododendrons, and it can be grown in many gardens with ease.
Mountain Laurel is ideal for shady gardens, and it also thrives in full sun if the soil is moist. Smaller varieties are perfect along the edges of beds, and larger ones as background shrubs in your borders. It fits beautifully into woodland and natural settings, but it looks just as wonderful around your home in a more formal setting. Besides the lovely and long display of buds and flowers, the evergreen foliage is always attractive. If you don’t have suitable soil, the smaller varieties in particular are ideal for growing in pots, where they can be placed in prominent places when in bloom, and then grown elsewhere for the rest of the year.
A broad, upright evergreen shrub, the Mountain Laurel has an attractive multi-stemmed form, and depending on the variety it can be between 3 to 10 feet in height, with a matching spread. The stems are hidden by the leaves in younger plants, but as the plants mature the thick base becomes visible. It has attractive bark that sheds in strips, and develops a striking, gnarled look with age. The leaves are deep green, leathery, glossy, and they often have undulating or waving edges. They are oval, between 2 and 6 inches long, depending on the variety and the final size of the plant. The may be more or less slender, again depending on the exact plant you grow. New shoots may be dark red, adding interest as they develop.
The flowers of the Mountain Laurel open in May and June, but they are colorful and interesting from much earlier. During winter, flower clusters begin to develop at the ends of every branch, expanding steadily into a large cluster of buds. These are fascinating, each one looking like it was made with an icing spout, with five fluted ridges down the sides. In spring the buds grow and enlarge, and they are often very colorful – deep red or pink – making a great show for weeks and weeks.
Eventually the waiting is over, and the flowers open towards the end of May. Each flower is large, around 1-inch across, and shaped like a 5-sided rice bowl. There are many flowers in each cluster, and when a bush is in bloom the foliage is almost completely hidden by the wonderful and long-lasting display of this fabulous shrub. The flowers have 5 prominent stamens in them, which add to the beauty of the bloom, especially with lighter colored flowers. Flower colors vary with the variety, and they can be white, shades of pink, or red, with or without dark bands and spots around the inside rim of the open bowl. Often the inside of the flower is a strong contrast with the outside. All in all, this is one of the most spectacular flowering shrubs you can grow, and more than worthy of a place in every garden.
Kalmia latifolifa – Mountain Laurel. This is the most important member of the small group of flowers called Kalmia, and the only one widely grown in gardens. Also known as Spoonwood or Calico Flower, this plant is native to the eastern states of America, growing all the way from New England into northern Florida, and in parts of Indiana and Louisiana as well. They grow in many places, but they are typically found growing in rocky or sandy open woodland areas, out in damp meadows, around the edges of woodlands, and on the slopes of mountains. It grows into a large shrub to 15 feet tall, or even a small tree to 30 feet in the Appalachians. The flowers are usually white or pale pink, but darker plants can sometimes be found in the wild.
For a long time, the Mountain Laurel was not widely grown in gardens, and only produced by a few specialist nurseries. Its development into a wonderful garden shrub is mainly due to decades of work by Richard A. Jaynes. He was a geneticist and plant breeder at the Connecticut Agricultural Experiment Station, New Haven, from 1961, before retiring in 1984 to his nursery, the Broken Arrow Nursery in Hamden, Connecticut. He began with unusual wild plants he and his students collected, and the few garden varieties that already existed. He then bred them together, raising the seedlings and selecting the very best. Many of the top varieties grown today, and the most colorful, are due to the careful and tireless work of Jaynes. Other breeders have created wonderful new plants too, including John Eichelser from Olympia, Washington, and European breeders as well.
Today there are many beautiful varieties of Mountain Laurel available, ranging in size from low edging shrubs to larger background plants. Flowers vary in color from white to dark reds, often with contrasting colors between the closed bud and the open flower. The wild variety called fuscata has a band of dark red inside the rim of the open flower, and it has contributed genes that have given us varieties with broad red bands, dots, splashes and ‘star-bursts’ of darker coloring inside the flowers.
Here are a few of the best varieties of the Mountain Laurel:
Kalmia latifolia var. myrtifolia – Myrtle-leaf Mountain Laurel
This naturally-occurring wild form has much smaller leaves, and so it is perfect for smaller varieties, which are very neat and compact. They are ideal for growing in pots.
Although more suited for wild and natural gardens, and important native wildflowers, there are other species of Kalmia sometimes available:
Kalmia angustifolia – Sheep Laurel. This low, spreading shrub from the north-east has small rose-pink to red flowers. Several garden varieties are available from time to time.
Kalmia buxifolia – Sand Laurel. A low-growing plant from the eastern states, with small oval leaves and white flowers.
Kalmia cuneata – White Wicky. This rare plant is found in the marshes of the Carolinas. It is a deciduous shrub with white flowers.
Kalmia polifolia – Eastern Bog Laurel. A low-growing shrub found in bogs, with rose-red flowers that open in April. Some garden varieties exist.
If you can grow Rhododendrons, Azaleas and Camellias in your garden, you can grow Mountain Laurel too, with ease. Even if your soil is not quite right for those acid-loving plants, if it is not very alkaline you should find that the Mountain Laurel grows well. If you don’t have suitable soil, then growing in pots and planters is the answer, and with their fibrous roots these plants will grow happily for years in pots.
The Mountain Laurel is hardy in zone 5, and it grows throughout zone 9 as well, so it can be grown in most gardens. It grows in both sun and partial shade, with full sun being ideal in cooler zones, and in regions that have a lot of cloudy days. In warmer areas morning sun and afternoon shade is ideal, and this plant will also grow in light full shade, such as beneath tall deciduous trees, and places in shade but with overhead clear sky. Those could be on the north side of a building, at the foot of a wall, or in the shadows to the south of trees and along the margins of woods. This adaptable plant will grow well in a range of light conditions, but avoid deep, dark shade, such as beneath evergreen trees.
The ideal soil will be moist, well-drained and rich, with a pH value of 6.5 or lower. Add plenty of rich, lime-free organic material such as rotted leaves or peat moss when planting. Soils between 6.5 and 7.0 will probably also be acceptable. The soil must have good drainage, and these plants prefer sandy soils, and don’t grow so well in heavy clay. If you have heavy soil, plant on a slope and add lots of organic matter.
If you have unsuitable soil, or limited garden space, the Mountain Laurel grows well in pots. Choose smaller-growing varieties, and always use pots with drainage holes. Pot them in soil blended for acid-loving plants and place in a suitably-lit location.
Newly-planted Mountain Laurel should be watered regularly, and not allowed to become dry. This plant doesn’t have a lot of drought tolerance, and it won’t grow well without a steady water supply. Mulch over the roots with lime-free organic material in spring, to conserve moisture and keep the soil cool. This, and regular watering, is especially important when your plants are in full sun. Pests and diseases are not normally problems at all, and if you have suitable soil, enough moisture and appropriate light, this is an easy, low-maintenance shrub to grow.
Water plants in pots and planters whenever the top inch of the soil is dry, and always water until some flows out of the drainage holes. Do not leave a plant standing in a saucer of water. Feed potted plants regularly from spring to early fall with liquid fertilizers recommended for Rhododendrons or azaleas. Regular mulching will take care of the nutrients for plants growing outdoors, but some supplementary Rhododendron fertilizer will give optimal results.
All parts of the Mountain Laurel are poisonous to most animals, and humans. Cases of poisoning in humans are very rare, but keep them away from horses, goats and other grazing animals.
No particular pruning or trimming is needed, and plants should be left to develop their own natural form. Since the flower buds form at the ends of the stems, cutting or trimming them will stop your plant from flowering. After the flowers are finished, remove the old flower heads carefully, just above the first leaves, as the seed-heads are not particularly interesting or attractive, and removing them will divert all the plant’s energy into flowers for next year, rather than into seeds. This will give you more blooms and a more colorful show next year.
If you are not familiar with the Mountain Laurel, you have a big treat in store. These wonderful shrubs are difficult for nurseries to produce with traditional methods, and this was always a factor in their low availability to gardeners. Today they are reproduced through the wonders of tissue culture, where a few cells from a single bud can be turned into hundreds of plants in test-tubes. These are grown under lights and then transplanted into pots, where they develop and grow just like traditional cuttings do. This technique has made them much more available, especially for their many special varieties, so don’t miss out, and plant some in your garden. You won’t believe the great beauty of this gorgeous shrub, and how easy it is to grow.