Mountain Arnica Arnica latifolia – Native Plant of the Week

Introduction

Mountain Arnica, Broadleaf Arnica, or Arnica latifolia is a common native wildflower found in the mountains of western North America. The Arnica genus has numerous species and is well-known to herbalists, wildflower enthusiasts, and nature lovers alike.  In the summer, when you go up the mountains, you are often greeted by their abundant cheerful yellow blooms. 

There are actually numerous different species of Arnica in North America, and often, to the untrained eye, they can be difficult to tell them apart. However, with a little training on the physical characteristics of the Asteraceae flowers they can readily be identified (see Description below). Fortunately, however, if you are wanting to use them medicinally many of the Arnicas share similar medicinal properties.  However, some species are rarer than others. So if you are doing any ethical wildcrafting, please keep this in mind. Check for rare species in your area to ensure you are not picking from rare plants. 

Description of Mountain or Broadleaf Arnica

Leaves & Stem

Broadleaf Arnica or Mountain Arnica is a perennial herb 10-60 cm tall from simple stems that are sometimes branched. It grows from a sturdy rhizome and produces hairy flower stalks that rarely have more than 2-4 pairs of leaves on them. There are, however usually numerous leaves growing in a rosette around the base of the flower stalks. The 2-10 cm long leaves are usually toothed and may or may not have leaf stalks (petioles). The leaves are usually broadly lance-shaped but can vary from lance-shaped to almost heart-shaped (cordate).

Flowers & Fruit

The flowers are yellow sunflower-like flowers typical of the Asteraceae family. There are 1-5 flower heads per stalk with anywhere from 8-15 ray florets (the ‘petals’ of an Asteraceae compound flower) per flower. The ray florets surround a slightly darker yellow central disk of 20-90 disk florets (tiny little flowers in the central area of an Asteraceae compound flower). If you want to learn more about Asteraceae flowers and their unique physical characteristics, I suggest you check out the diagrams here https://cronodon.com/BioTech/asteraceae.html . You can also read the Wiki page on Asteraceae, it is very informative. However, the above link has much better diagrams showing the different physical features of the composite flowers.

The bracts surrounding the compound flower (involucres) are narrowly shaped like a spinning top (turbinate). There are from 8-20 lance-shaped or reverse lance-shaped (oblanceolate) phyllaries (the second set of bracts surrounding the base of Asteraceae flowers) below the involucre bracts. Their reduced calyx or sepals (pappus) is seen as a white and bristly tuft of hairs outside the corolla of each of the tiny little florets.

Their fruit is known as a cypsela, a small seed with a hairy tuft of a pappus that remains attached, aiding in dispersal by wind. The cypsela is dark brown, 5-9 mm long, and sparsely covered with long, soft, straight hairs (villous).

Similar Species Frequently Confused With

Different species of Arnica are usually distinguished by their leaf shape, florets, cypsela, pappus, and their involucres. There are numerous species in North America all with a similar superficial appearance. The variability in leaf shape, and similar habitat preferences, can make Arnica latifolia easy to confuse with Arnica cordifolia in particular with its heart-shaped (cordate) leaves. In the case of Arnica cordifolia, its leaves are heart-shaped (cordate), never lance-shaped, and always have petioles. Furthermore, Arnica cordifolia typically has fewer ray florets and their involucres are broadly bell-shaped (campanulate). Finally, the cypsela of Arnica cordifolia is 5-10 mm long, dark grey, and sparsely to densely covered in coarse, long, rough hairs (hirsute) and sometimes may be covered in stalked glands (stipitate-glandular).

Habitat & Growing Conditions of Mountain Arnica

Mountain Arnica, Broadleaf Arnica, or Arnica latifolia is native to western North America. It is typically, though not exclusively, found in relatively moist montane to subalpine forests from 500-3300 m in elevation. As you increase in latitude, the elevation it is found at decreases, as with most wildflowers. It grows in both forests and open meadows. It is often seen growing along the side of logging roads and even in older clear-cuts, providing these have enough moisture.

Mountain Arnica is usually found in full sun to part shade. In hotter climates, it prefers part shade but prefers more sun as you move north. It prefers sandy well-drained, slightly alkaline soils. But it can also be found growing in a variety of soil types as long as they are well drained as it will not grow in waterlogged soils.

Growing Mountain Arnica in Your Garden

Arnica latifolia can be relatively easy to grow if the conditions are suitable. If you live in a mountainous area in western North America, you should have no problem growing it. If you live in a dry climate, it may be more challenging to grow it in your yard, but it can be done. Arnica tolerates full sun to part shade and prefers moist but well-drained soils. Be sure to amend your soil with some organic compost for food and moisture retention. Otherwise, being a native species, it will require little to no maintenance once it becomes established in your yard.

If you have heavy clay or very sandy and gravelly soils you should dig out a pit of soil and fill it with a humus-rich topsoil instead. Then plant your seeds or your plants in the pit you created. If your land tends to be waterlogged (heavy clay soil), then place the plants or seeds on a mound higher than the surrounding soil so that it can get extra drainage. If your land tends to drain too quickly after a rain (lots of gravel and sand) then place the plants or seeds in a small depression so that it collects and holds water better for longer periods of time. Again, once established, they should require little to no maintenance.

Wildlife Values of Arnica

Nothing could be found on the wildlife values of Arnica latifolia. If you know of some please Contact Me!

Distribution of Mountain or Broadleaf Arnica

In Canada, Arnica latifolia is found in the Yukon and Northwest Territories, as well as in British Columbia and Alberta.

In the USA, it is native to Washington, Oregon, California, Idaho, Montana, Colorado, Wyoming, Nevada, Utah, and New Mexico. According to iNaturalist it may also be found in Arizona, USA.

According to iNaturalist Arnica latifolia may be found in Mexico in the states of Sinaloa and Jalisco. Those reports, however, are all as of yet unconfirmed. Arnica latifolia is a highly diverse species, and there are many species of Arnica that resemble each other making positive identifications challenging for the untrained. So we could assume its southern limit maybe California and New Mexico, and the northern limit is Alaska, Yukon, and Northwest Territories.

Status of Arnica latifolia

Mountain or Broadleaf Arnica is considered Secure (G5). However, it is only Secure (G5) in British Columbia, Canada. It is considered Apparently Secure (S4) in Alberta, Canada. In the Yukon and Northwest Territories, it is considered Vulnerable (S3). It is considered Vulnerable (S3) in Utah and Wyoming in the United States. In all other states where it is located, it is as of yet Unranked, as is the case of many native plants in that region.

Traditional or Other Uses of Mountain Arnica

Arnica species have long been used in Europe in salves, tinctures, and ointments for their anti-inflammatory properties for sore muscles, stiffness, and bruises. It was also widely used for various first aid treatments as an antiseptic and antibacterial, for insect bites, and healing wounds. However, it should be noted that Arnica is no longer recommended for internal use due to possible toxic effects. Furthermore, many herbalists recommend that it be used only on unbroken skin due to the possibility of irritation in sensitive individuals. Despite these warnings, Arnica is still a widely used topical herbal medicine today.

There is less documented historical use of Arnica in North America compared to that of Europe. But native peoples in North America did sometimes use Arnica species. Poultices were made by the Thompson to reduce swellings, treat rheumatism, and for cuts and bruises. Catawba people used root decoctions internally back pain. Shuswap used an infusion externally for sore eyes.

The Okanagan-Colville used it as a love potion when mixed with the heart and tongue of a robin and red ochre.

Ethical Wildcrafting of Arnica latifolia for Medicinal Use

When wildcrafting, follow the 1 in 20 rule for flowers as described in the Ethical Wildcrafting post. For every 20 flowers you see, pick one. Do not pick all the flowers off a single plant instead, spread your harvest around. Alternatively, grow it in your garden, see the section above on Growing Arnica in Your Garden.

Find a nice large and healthy population of flowers to harvest from. If you find just a few plants or a single plant, please leave them alone to reproduce. Arnica flowers should be picked in the summer when in full bloom but before they start to go to seed. Do not pick the flowers when they are wet with dew or rain to help prevent molding. Also, do not pick in the heat of the day if the flowers look ‘droopy’. The quality will be poor and it is more damaging to the plant. The goal is to leave the plant alive and still thriving when you are done.

Wildcrafting and Processing

To pick the flowers, simply pinch them off their stalks at the base of the flower. They are easily plucked from their stems this way, but if you find them tough use a knife, scissors, or hand cutters to cut them off (See Resources below). Never pull the stalks out to harvest the flowers or you could damage the plant so that it may not survive the following year. Once the flowers are picked, they can be placed in a basket or a paper bag. I always use a paper bag for wildcrafting and I carry a sharpie with me to write the date, species, and location of harvest. I re-use my bags over and over again.

When you get them home dry them in a single layer on a drying rack or an old window screen works great. You can dry flowers on a flat surface like a table, but be sure to turn them daily to prevent molding. Once dried, your harvest can be stored in glass jars until you are ready to use it. Never pre-grind or crush your herbs before storing as this dramatically reduces their shelf life. Instead, store them whole and dried. Then you can crush or grind as needed when you are ready to use them.

References and Resources

Canadensys Plant Search https://data.canadensys.net/vascan/search

Cronodon Asteraceae Flower Diagram https://cronodon.com/BioTech/asteraceae.html .

Dictionary of Botanical Terms – by Lyrae’s Nature Blog https://lyraenatureblog.com/blog/dictionary-of-botanical-terms/

Eflora Plants of North America http://www.efloras.org/browse.aspx?flora_id=1

iNaturalist Plant Search https://www.inaturalist.org/home

Native American Ethnobotany http://naeb.brit.org/

NatureServe Explorer https://explorer.natureserve.org/Search

USDA Plants Database https://plants.sc.egov.usda.gov/home

Willis, Lyrae (2022).  Plant Families of North America.  Not yet published. 

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