Read a commented mountain laurel profile here with explanations of toxicity, winter hardiness, leaves and flowers. Planting and care tips worth knowing for Kalmia latifolia in beds and pots.
What characterizes mountain laurel?
The mountain laurel (Kalmia latifolia) is an evergreen shrub from the heather family that impresses with its bushy growth habit, colorful flowers and laurel-like leaves. The plant is hardy, long-lived, easy to care for, but poisonous and should be cared for with lime-free water and acidic leaf compost.
Profile
- Scientific name: Kalmia latifolia
- Family: Heather family (Ericaceae)
- Synonym: Broad-leaved laurel rose
- Origin: North America
- Growth type: evergreen shrub
- Growth height: 100 cm to 200 cm
- Growth habit: upright, bushy
- Leaf: elliptical-lanceolate
- Flower: racemose, cup-shaped
- Toxicity: poisonous
- Winter hardiness: hardy
- Use: ornamental plant, potted plant
Growth
Mountain laurel (Kalmia latifolia) is a species of plant from the genus laurel roses (Kalmia) within the heather family (Ericaceae). The evergreen shrub is native to North America. In this country, the exuberantly flowering tree is often planted in beds and containers. The laurel rose is closely related to rhododendrons and azaleas, which is reflected in these growth characteristics:
- Growth habit: bushy, upright shrub with evergreen, laurel-like leaves, pink-red buds and colorful goblet flowers in spring.
- Growth height as a bed and container plant: 60 cm to 200 cm.
- Growth height in North America: 200 cm to 800 cm.
- Roots: Shallow roots
- Growth rate: 5 cm to 15 cm annual growth.
- Ghorticulturally interesting properties: easy to care for, avoids lime, hardy, long-lasting, blooms profusely, friendly to bees, poisonous, slow-growing, sensitive to cuts.
Leaf
Mountain laurel with its dense foliage is a feast for the eyes at any time of the year. The shapely leaves are characterized by these features:
- Leaf shape: elliptical to lanceolate, laurel-like.
- Leaf color: evergreen, medium green.
- Leaf size: 4 cm to 12 cm long, 1.5 cm to 5 cm wide (hence the second name broad-leaved laurel rose).
- Texture: leathery, shiny.
- Arrangement: alternate, clustered in a lively manner.
Bloom
Decorative, red buds and fabulous abundance of flowers are the trademark of mountain laurel. The picturesque festival is rounded off by a remarkable mechanism that forces pollen transport on pollinator insects. The following overview provides flower details worth knowing:
- Inflorescence: Raceme with 20 to 40 individual flowers.
- Single flower: stalked, fivefold with double perianth, goblet or bell-shaped.
- Flower color: pink (mountain laurel varieties bloom multicolored white to pinkish red, spotted or dotted in the flower center).
- Flowering time: May to June.
- flower ecology: hermaphrodite
- Pollinators: Insects of all kinds, primarily bees, bumblebees and butterflies.
Mountain laurel has equipped its flowers with a clever mechanism for optimized pollen distribution. Parallel to the flower growth, the stamens build up tension. When an insect lands on the flower, the stamens shoot up and throw the pollen onto the insect's body. The following video from the Royal Botanic Garden Edinburgh demonstrates the fascinating process:
Video: Ingenious strategy for effective pollen distribution
Toxicity
All parts of a Kalmia latifolia plant are poisonous. The main toxic substance is acetylandromedol. The toxin causes allergic reactions, irritation of the oral mucosa, nausea, vomiting, diarrhea and circulatory problems, including cardiac arrest. Children, pets (dogs, cats, rabbits) and grazing animals (sheep, goats, horses) are particularly at risk.
Usage
Mountain laurel, with its decorative properties, is a source of inspiration for these creative uses:
| Garden Style | Tips & Ideas |
|---|---|
| Rhododendron bed | Flowering period extended until the end of June with mountain laurel. |
| Cottage Garden | Kalmia as a flowering border. |
| Mediterranean Garden | Mountain laurel as a hardy alternative to tulip magnolia. |
| Front yard | Laurel rose as a house tree. |
| Forest Garden | Underplanting large trees with mountain laurel. |
| Heidegarten | Enclosure made of laurel rose hedge. |
| Balcony | Potter plant with privacy effect. |
Planting mountain laurel
The best time to plant mountain laurel is in spring. From mid-February you can buy ready-to-plant calmias at the nursery for 25 euros for a 20 cm small bush. Representative laurel roses with a height of 70 cm to 80 cm cost from 220 euros. You can find out where and how to plant Kalmia latifolia correctly here:
Location, soil, substrate
These are the most important location conditions for mountain laurel in beds and pots:
- Sunny to partially shaded, wind-protected location.
- Fresh to moist, acidic garden soil, humus-loose and nutrient-rich.
- As a container substrate, preferably rhododendron soil without peat (e.g. Floragard Bio Rhodohum).
- Ideal pH value 4.5 to 5.5 (can be determined using test strips from the garden center).
- Extra tip: The flower color stays longer when placed in partial shade.
Planting Tips
In preparation for planting, please place the potted root ball in a bucket of rainwater. These tips get to the heart of what is really important when it comes to the right planting technique in beds and pots:
- Gloves with cuffs, rubber boots and long trouser legs protect against skin contact with the poisonous plant parts.
- The planting pit has twice the volume of the potted root ball.
- For initial fertilization, one third of the excavated material is mixed with acidic leaf compost or rhododendron soil.
- A 5-10 cm high layer of expanded clay serves as drainage on the bottom of the pit or the bottom of the bucket.
- Mountain laurel is planted just as deep in the bed and pot as before in the nursery pot.
Last but not least, press the soil firmly with both hands and water thoroughly with lime-free water. As a bed and container plant, mountain laurel benefits from a layer of mulch.
Excursus
Homage to Pehr Kalm
Carl von Linné honored his student Pehr Kalm (March 1716; November 1779) by naming the ten types of laurel roses Kalmia. The Swedish naturalist was one of Linnaeus's legendary 17 apostles, who traveled around the globe as daring plant collectors. As a student in North America, Pehr Kalm sent the first Kalmia specimens to his mentor and professor.
Care for mountain laurel
Mountain laurel is easy to care for, as long as you take into account its aversion to hard tap water and calcareous fertilizer. The flowering shrub loves moist soil without waterlogging. Nutrient requirements are easy to cover. Occasional pruning care promotes the blooms. As a container plant, the laurel rose is grateful for light winter protection. It's worth taking a look at these care tips:
Pouring
- Water mountain laurel as soon as the soil surface is noticeably dry (finger test provides information).
- For watering, only use lime-free rainwater, skimmed pond water or decalcified tap water.
- Mulching keeps the soil moist and weed-free for longer.
Fertilize
- Fertilize the bed plant in spring with acidic leaf compost and a handful of horn shavings.
- Add liquid rhododendron fertilizer to the water every month for potted plants from April to August.
Cutting
You can cut a mountain laurel like a rhododendron. Gloves, safety glasses and a face mask are mandatory for cutting care. You can read detailed cutting instructions here. Important information on cutting Kalmia latifolia can be found here in brief:
- Clean out wilted flowers so that new buds can develop.
- Do not cut mountain laurel in the first five years.
- Thin out older bushes in February.
- Cut off annoying, bent and excessively long branches before flowering.
The correct cutting technique is a combination of lead cut and tenon cut. As the intersection point, choose a fork between the relevant branch and a promising side branch. The cut leaves a 3-5 cm small cone with a leaf on the side.
Wintering
- In the year of planting, cover the root disk with leaves and coniferous twigs (recommended in rough locations).
- Place the laurel rose as a potted plant on wood every year before the first frost and wrap the pot with fleece.
- When there is a frost, water mountain laurel in the bed and in the container on mild days.
Transplanting, repotting
You can transplant a mountain laurel in its first five years. With each additional year, the probability of failure increases disproportionately. The best time to change location is when the sap is dormant, ideally in autumn.
As a container plant, you should repot a mountain laurel every two years in fresh rhododendron substrate. Because mountain laurel grows very slowly, you can reuse the previous pot.
Propagate
When it comes to propagation, the laurel rose shows its stubborn side. Cutting cuttings leaves unsightly gaps in the slow-growing bush. Furthermore, there is a high failure rate when rooting offshoots. Mountain laurel propagated by sowing takes at least five years until the first flowering period. To make matters worse, only the seeds of the wild form germinate.
Diseases and pests
Mountain laurel is a resilient shrub. However, a plant weakened by care errors is susceptible to diseases and pests. Watering with hard water causes leaf chlorosis. This deficiency manifests itself as yellow leaf discoloration. Overfertilization causes leaf edge necrosis. Occasionally, voracious weevils nibble on the leaves.
Popular varieties
These mountain laurel varieties transform the bed and balcony into a colorful sea of flowers:
- Mountain laurel 'Carousel': new variety with pink-white buds that develop into star-shaped flowers, height 100 cm to 150 cm.
- Mountain laurel 'Minuet': Premium variety, white bell flowers with a dark red border, beautiful as a container plant, height 80 cm to 150 cm.
- Laurel rose 'Sterntaler': evergreen leaves contrast picturesquely with dark red cup flowers, which adorn a white-red center, height 120 cm to 150 cm.
- Mountain laurel 'Ostbo Red': richly blooming laurel rose with bright red buds and light pink goblet flowers, accompanied by evergreen, laurel-like leaves, relatively short flowering period from mid-June to the end of June, height 80cm to 100cm.
FAQ
Is the laurel rose poisonous?
Yes, all parts of a laurel rose are highly poisonous. Unprotected skin contact with the plant sap can trigger stubborn allergic reactions. Consuming leaves, flowers or seeds causes distressing symptoms of poisoning, such as nausea, vomiting and diarrhea in humans and animals. In the worst case, oral ingestion of Kalmia plant parts leads to circulatory collapse and cardiac arrest. For this reason, laurel roses are planted out of the reach of children, domestic animals and grazing animals.
Is Kalmia latifolia hardy?
A planted Kalmia latifolia is completely hardy. The broad-leaved laurel rose can cope with bitter frost down to -35° Celsius and colder without any injuries. Light winter protection is only required for potted plants. A fleece coating protects the root ball against frost damage. A wooden foot prevents frosty ground cold from finding its way into the root ball.
Our old mountain laurel is balding at the base. What to do?
Over the years, mountain laurel tends to become bald at the base of the bush. It is a natural process that cannot be completely prevented by regular thinning. You can cleverly conceal the bare lower area with an underplanting of perennials. Beautiful companions for a laurel rose are colorful purple bells (Heuchera villosa), snow feather hostas (Hosta undulata 'Univittata') or shade-tolerant fairy flowers (Epimedium).
