Mountain Laurel 101 – Complete Grow and Care

If you hike in the Appalachian Mountains in late Spring, you may be treated to one of the most striking wildflower displays you could ever hope for in your life. Mountain Laurel is an understory shrub that blooms profusely in colonies that dot the Appalachian Mountains, and is truly stunning. So let’s learn all about this tough evergreen showy shrub below.

Mountain Laurel is a showy, flowering evergreen shrub native to Eastern North America. Scientifically known as Kalmia latifolia, it typically grows to 10′ tall and forms dense colonies in the forest. This understory shrub prefers rich humus soil that drains well and is lightly acidic.

I believe this to be one of the showiest plants you can encounter in the wild. Shortly after moving to Pennsylvania, I was hiking in the Appalachian Mountains when I first came upon a dense grove blooming profusely.   

Dozens of Mountain Laurel shrubs were peppered with pollinators, and just looking overwhelmingly beautiful.  This is one of the most beautiful native shrubs you can encounter.

In yards and gardens, Mountain Laurel will typically grow to about 10′ tall by 10′ wide (3 m x 3 m).  In the wild, this shrub can reach 15-20′ in height and form somewhat dense thickets and colonies.  Sometimes the thickets are almost impassible, as any hunter will tell you. 

It’s wild and gnarly.  The branch structure surrounded by the waxy evergreen leaves looks really cool and is guaranteed to draw interest from passers by.  When blooming Mountain Laurel will put on a glorious display of white/pink flowers clustered together that are about the size of softballs.

 Facts

• Mountain Laurel is native from Louisiana to Indiana, then East to the Atlantic Ocean and New England.
• Mountain Laurel is the state flower of both Connecticut and Pennsylvania [1] [2].
• Very Adaptable! – Mountain Laurel can grow in both full shade and full sun.
• Mountain Laurel will keep its waxy leaves year round, making it an attractive evergreen, similar to Rhododendron.
• It is hardy from zones 4-9, check your USDA zone here.
• Mountain Laurel is the host plant to the Laurel Sphinx Moth
• All parts of Mountain Laurel are toxic.  Honey made from Mountain Laurels will also be toxic – so avoid this plant if you are a beekeeper!

Mountain Laurel Quick Reference Table – Grow and Care

Common Name	Mountain Laurel, Calico Bush
Scientific Name	Kalmia latifolia
Native Range	USDA Zone 4-9, Eastern United States
Bloom Time / Duration	Spring – lasting several weeks
Height	5′-20′ (1.6 m – 7m)
Spacing	5′-15′ (1.6 m – 5m)
Light Requirements	Full sun to Full Shade
Soil Types	Soil rich in organic matter and humus, acidic
Moisture	Well drained, medium moisture.
Maintenance	Can be pruned to shape, pull unwanted seedlings
Garden Use	Understory tree, border/privacy, single specimen focal point
Fauna associations	Attracts bees and birds

Mountain Laurel Growth Rate

Mountain Laurel will typically grow approximately 5″ in height, and about 3″ in crown diameter, per year [3].  So, the annual growth rate of Mountain Laurel is low at less than 1′ per year.

Growing Conditions for Mountain Laurel

Mountain Laurel is a lovely plant, but it won’t grow everywhere.  It needs to have good drainage and slightly acidic soil to thrive. 

If you have clay soil, you may consider other types of evergreen shrubs that are more adaptable.  It is possible to amend clay soil to become acidic, but it takes a lot of effort.

Natural Habitat of Mountain Laurel

You can find wild Mountain Laurel growing in the Appalachian Mountains, riparian habitats, in the Piedmont, and near forests.  Mountain Laurel generally grows in established forests, so very loose and hummus-rich soil.  Since it is an evergreen, it is quite easy to locate specimens just driving through the mountains during winter time.

The main point is that if you want to grow Mountain Laurel at your home, it is best to recreate its natural habitat.

Grow and Care for Mountain Laurel

Mountain Laurel will grow in either full sun or full shade, and everything in between.  It likes to have medium moisture available, and well drained soil.  I would not attempt to grow Mountain Laurel in clay soil, as it is very difficult to lower the pH, and generally doesn’t drain well.

Like most evergreen plants Mountain Laurel likes to have slightly acidic soil.  Soil that is sandy, rich in hummus, or very loose will be a good candidate for acidifying.

Checking the pH of your soil

To determine the pH of your soil, an inexpensive soil tester will work, or taking a coffee can full of soil to your local ag extension office where they often test it for free. But on our recommended products page we have a soil tester that generally costs around $10.

If you find that you need to lower the pH of your soil and make it more acidic, there are several options.  The best option would be to heavily amend the soil with Peat Moss.  And I mean heavy.  Then, retest your soil after moistening.

How to care for Mountain Laurel

Mountain Laurel will do great if grown in full or partial shade, with adequate water available, and it good well-draining soil that is slightly acidic.  However, if growing in full sun – you will likely have to add supplemental water.

Maintenance

Pruning of Mountain Laurel may be required, or desired.  If the branches start growing against the siding of your house, you should prune them back.  Otherwise most pruning should be to done to keep a desired shape.  Pruning should be done in Early Spring, while the plant is still dormant.

But, Mountain Laurel can survive pruning and regrow in a few years.  So, don’t be shy with the clippers.

How to Establish Mountain Laurel

If transplanting Mountain Laurel, first make sure you have the appropriate soil (described above).  If so, you may still elect to add hummus, compost, and possibly peat moss to the hole.

• Dig a hole that is twice as wide, and 1.5x as deep as the pot the plant is currently in.
• Amend the soil with hummus, compost, and sphagnum peat moss.
• Fill the hole with water, and wait for it to drain
• Add in more amendments (mixed with soil) to get the depth of the hole to just slightly shallower than the pot (this helps ensure good drainage).
• Plant the Mountain Laurel, and backfill.
• Water again

How to save Mountain Laurel seed

In Fall or Winter, you can harvest Mountain Laurel seed. At the locations on the plant where the flowers were, seed capsules will form on stems. These are normally at the top of branches, and they often occur in clusters.

Simply pull off the capsules and place into a baggy. Let the capsules dry for another week in a cool dry place in a breathable container. Then, simply crush the capsules to release the extremely tiny seeds.

The seeds are tiny little flakes that are roughly 1/64″ (0.4 mm) wide by 1/32″ (0.8mm) long.

How to Grow Mountain Laurel from Seed

Mountain Laurel seeds require three things to germinate.

1. A 60 day cold stratification period, or winter sowing
2. Surface Sown with good contact with a potting soil
3. Moisture

So, gather seed from the wild in the Fall.  Then, prepare some pots with a potting soil or seed starting medium.  Sprinkle Mountain Laurel seed right on top of the soil, and press down with your thumb.

Then, winter sow the pots or milk-jugs outside in the winter.  It is best to keep the pots in an area where they will receive morning sun, and shade in the afternoon. 

Finally, just keep the pots moist until temperatures begin to warm up. Once daytime temperatures reach 60 degrees Fahrenheit remove any covering or dome. Then, just keep the soil moist. It can take a couple of months for the seeds to germinate.

It can take a very long time for the seeds to germinate. I winter sowed my seed around February, and it did not germinate until sometime in July.

Garden Uses

Mountain Laurel can make for a beautiful display year round, in full sun or full shade.  It can be a centerpiece of a flower bed, in an island garden within your lawn, or make a privacy border.  If you live in a wooded area, then Mountain Laurel is likely an excellent choice for a woodland garden.

Mountain Laurel’s showiness can give your home great curb appeal and interest throughout the year.  Because the plant is native, you can also take pride that you aren’t unwittingly spreading invasive plants, like the common butterfly bush.

Fauna

Pollinators

Bees and hummingbirds will pollinate Mountain Laurel.  Also, Mountain Laurel is host to the Laurel Sphinx Moth. Note that due to it’s toxicity, any honey made by bees pollinating Mountain Laurel should be avoided.

Pests and diseases

Mountain Laurel is susceptible to leaf-spot. The primary symptom is black spots on the leaves. This generally occurs when there is not enough air movement through the plant, or area it is planted in.  So, consider some selective pruning to ensure adequate air flow through the interior of the plant.

Deer and Rabbits

Due to the toxic and bitter foliage, deer and rabbits avoid Mountain Laurel. This is one native plant that can definitely withstand deer pressure!

Mountain Laurel Physical Description

Height

Mountain Laurel will grow up to 15′-20′ (5-7 m) tall depending on conditions.

Overall Shape

Mountain Laurel can resemble a round bush/shrub, or a small tree depending on where it is grown.  Technically Mountain Laurel is a shrub, and will grow foliage where ever sunlight is available.  So, it out in the open in full sun, you can expect a more rounded appearance of foliage.

If grown under a dense canopy of trees, it would grow more like a small ornamental tree.  That is because the main sunlight available will be from the top.  So it will grow its leaves to catch the dappled sunlight from above.

Trunk/Bark

Mountain laurel will grow a very crooked/gnarly, and interesting trunk.  It will have erratic branching and may have a strange shape.  The bark is veined, with outer layers slightly peeling.

Leaves

Individual leaves of Mountain Laurel are lance-shaped, or slightly oblong/oval about 1″ wide (2.5 cm) by 2-3″ long (5-7 cm), with a point/tip at the end.  The edges/margins will be smooth.  Leaves have a waxy feel to them.  They are quite stout, resisting tearing.  This is an evergreen, so the leaves will stay year round.  The color is generally a dark green (if shaded), or more pale/yellow green if in full sun or new growth.

Mountain Laurel Flower

Flowers of Mountain Laurel will appear in clusters that are about 3-6″ diameter (7-15 cm).  The clusters will grow from the center of a leaf cluster.

The color of individual blooms will be pink to white.  Often the buds are pink, turning white when they open up.  There will be approximately six petals per flower.  In the wild, the petals will be white with dark red markings in the middle and margins.  After blooming, nutlets will form that contain dozens of tiny seeds when opened.  These can be collected throughout the winter if one wishes to propagate the plant further.

Root

The root system of Mountain Laurel is quite shallow.  The plant evolved to cling to even the barest of rock outcroppings with minimal soil available.

Toxicity

All parts of Mountain Laurel are toxic. Honey made from Mountain Laurel flowers is toxic and should be avoided. If sufficient amounts of the plant are consumed symptoms of poisoning may develop in approximately six hours and may include stomach aches, watering of eyes/nose/mouth. If severe, slow heartbeat and respiratory issues may develop, convulsions, paralysis of arms/legs, coma and possibly death within 12-14 hours. [4]

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