Kalmia

( KAL - mee - uh )

At-A-Glance Information

Kalmia is a genus of flowering shrub that is a relative of Rhododendron. They are commonly called Lambkill, Mountain Laurel, Kill-Kid, and Spoonwood. Showy clusters of flowers open in summertime from buds that look like small, multi-pointed stars. These hardy shrubs are native to the eastern areas of North America and Cuba, and are at home in woods, swamps, and meadows. These popular garden shrubs will add beautiful foliage and floral shows to your yard. Take care when planting these in your yard, as grazing livestock, children and pets can be poisoned by eating the foliage.

Kalmia Species and Varietals

The genus Kalmia includes 10 species and is a member of the plant family Ericaceae. The genus Kalmia was named by Carl Linnaeus to honor his friend and fellow botanist Pehr Kalm. Kalmia growing zones depend on the species. See the species descriptions below for more information. To find your zone, click here: Zone Map.

Kalmia angustifolia (Sheep Laurel)
This species of Kalmia is native to eastern North America, and commonly grows in dry habitats, colonizing areas after fire or logging activities. It produces attractive, deep pink flowers in early summertime, and ranges in height from 6 to 35 inches tall when mature. There are many subspecies and cultivars perfect for garden cultivation.

Kalmia buxifolia (Sandmyrtle, Sand-Myrtle)
These plants are native to coastal areas of eastern North America. They reach up to just over three feet tall when mature, and produce white to pinkish flowers with protruding stamens. Leaves are green and oval to lance-shaped; the specific epithet 'buxifolia' means box-leaved, referring to the foliage similarity to Buxus spp. Cultivar 'Maryfield' is a choice garden ornamental.

Kalmia cuneata (Whitewicky, White-Wicky, White Wicky)
This species of Kalmia is native to North Carolina and South Carolina, USA, and can reach up to almost 7 feet tall. Flowers are white, and have reddish dots toward their centers.

Kalmia latifolia (Mountain Laurel, Calico-Bush, Spoonwood)
This shrub native to Eastern North America grows best in zones 2-7, 16 and 17. It is slow-growing and reaches 6-8 feet tall and wide. Glossy dark green leaves have a yellow hue underneath. Flowers are typically light pink or white and open from darker pink buds in late spring. Needs partial shade, but is hardy below 0 degrees Fahrenheit. Does better as a container plant in zones 16 and 17. Varieties are outlined below.

'Freckles'
Flowers with white spots and splashes of purple-red.

'Bullseye'
Cream-colored blossoms with white and purple-red markings on throats. New foliage is red.

'Firecracker'
Red buds open to pink flowers.

'Nathan Hale'
Pink flowers with red throats open from red buds.

'Olympic Fire'
Red buds open to pink flowers.

'Sarah'
Reddish-pink flowers open from red buds.

'Pristine'
White flowers

'Snowdrift'
White flowers with faint red markings on petals.

'Elf'
Dwarf variety, grows to 3 feet tall and wide in 10 years. Pink buds open to white flowers

'Minuet'
Light pink buds open to white flowers with a maroon ring inside. 3 feet tall and wide in 10 years.

'Tinkerbell'
3 feet tall and wide in 10 years (dwarf variety). Pink buds open to deep pink flowers.

Kalmia polifolia microphylla (Kalmia microphylla) (Western Laurel, Alpine Laurel, Western Bog-Laurel, Swamp Laurel)
Native to Alaska and Northern California, this small shrub gets to just 1 foot high and 8 inches wide. Small leaves are dark green on top, white underneath. Clusters of rose to purple flowers bloom in summertime. Grows best in zones A2, A3, 1-7, 16 and 17. Needs partial shade, but can take full sun in areas where summers are cool.

Kalmia procumbens (Apline Azalea, Trailing Azalea)
These dwarf shrubs typically don't reach over 4 inches tall at maturity, and have a wide distribution in the Northern Hemisphere. This species makes a great groundcover in cooler regions, and have very tiny dark green leaves and reddish-pink small flowers that bloom in summertime.

Caring for and pruning Kalmia shrubs

Kalmia shrubs need a somewhat moist atmosphere, and like to be planted in well-draining, humus-rich soil. Soil should be acidic, with a pH of between 4.5 and 5.5, and be kept moist. Plant Kalmia shrubs in partial shade (they can be grown in full sun exposure if the soil is kept consistently moist), and mulch around the base with pine needles. These shrubs are hardy to a temperature of up to -30 degrees Fahrenheit, and are considered easy to care for. Kalmia does not need to be fertilized much, though if your soil is particularly poor, fertilize with a balanced, slow-release feed in springtime. These slow growers do not need much in the way of pruning; simply remove spent flower heads to keep the plant looking tidy.

Propagation

Kalmia can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Kalmia, follow the instructions below:

Propagating Kalmia by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
In late springtime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch greenwood portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.

Propagating Kalmia by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
Harvest your seeds. The seed pods are pretty easy to spot, they're left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will begin to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
Kalmia seeds need to be cold-stratified before being sown. Place your seeds in a damp paper towel inside of a sealed plastic bag in your refrigerator and leave it there for about two months. Once this period has passed, remove the seeds from the bag and set them aside to dry out.
Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light and stays at a temperature of 75 degrees Fahrenheit. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes a month from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and a temperature of 75 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.