Arnica is an herbaceous, low-growing perennial that is hardy to USDA zones 2 to 9
Arnica is in the Asteraceae family and has lance shaped leaves that are light green and somewhat rough in texture. The plant grows approximately two feet in height and puts out bright yellow flowers starting in mid-July and continuing through the summer. Once establishes, Arnica produces extensive numbers of seeds that can be harvested for future plantings. It also spreads prolifically by rhizome growth. If left to its own devices, arnica will quickly fill in own spaces. There are several species of Arnica. We grow Arnica Chamissonis because it does better at our farms elevation; farmers in higher elevations may have greater success with Arnica Montana which prefers more acidic soil pH. There is a strong market for both species, and they are used interchangeably by many herbalists.
Native to western region of the United States and Canada, arnica can be found growing in the wild in acidic and rocky soils, usually in the higher elevations and mountainous terrain. Arnica is hardy to as low as zone 2 and when cultivated grows well in well drained , loamy soil and in full sun. It should be noted that while arnica is an avid spreader and will take over an area, it is not aggressive enough to smother perennial weeds. Therefore, careful elimination during bed preparation, prior to planting, is recommended. It can be difficult to remove weeds that are interspersed with the lovely, creeping arnica.
Arnica seeds are only viable for a short time, and it is recommended to use fresh seeds when planting. While there are mixed opinions about whether arnica seeds require stratification, we find ti helpful to stratify the A.chamissonis seeds for up to two weeks in the early spring in an unheated greenhouse. Seeds are light dependent germinators and are sown on the surface or covered lightly with potting medium. Seeds germinate in three to four weeks and should be transplanted out when they are well rooted. Arnica can also be propagated easily from root divisions and vegetative cuttings, which is our preferred method of making starts.
Arnica is a short, creeping perennial that requires full sun. Avoid planting it next o tall species, such as nettle, echinacea, or angelica, that can easily shade it. It takes at least a year to establish a solid patch of arnica, and it is often difficult to weed rogue plants out after the arnica begins to spread. Plant your arnica crop next to herbs that don’t easily self-seed and are more self-contained. We like to plant arnica next to our rhodiola and yarrow. Recommended plant spacing for arnica is six inches between plants, in triple rows with fourteen inches between rows. During the first year arnica will spread by rhizomes to fill in all open spaces between transplants, making a dense mat of living plants.
Arnica flowers have been used for centuries to make topical applications such as creams, oils, salves, and liniments to reduce inflammation and pain caused by trauma and overexertion. Arnica is commonly used to treat damaged tissue, bruising, sprains, breaks, and strains. Flowers can be used in their fresh or dried stages, and some herbalists also use the leaves in combination with the blossoms. On the farm we make solar infusions of arnica oil by using fresh blossoms and olive oil. We find arnica oil extremely beneficial for alleviating the muscular tension and fatigue that comes from log hours o repetitive and strenuous work.
Caution: Arnica is not to be used internally
With a healthy plot of arnica it is possible to get a light blossom harvest in the first year. However, the substantial yields come in subsequent seasons. In Washington, arnica begins to flower in late June, then continues to produce blossoms throughout the summer. In places in western United States and Canada, arnica has been known to flower into the fall. Harvesting arnica blossoms is a backbreaking, but rewarding endeavor. We hand-harvest because of the plants staggered blossoming pattern: some flowers are open and ready to harvest, some are in closed bud stage, and others are headed to seed. We find hand-harvesting multiple times during flowering is the way to go. During peak of harvest we are picking every three to four days.
Post Harvest Drying Conditions
Arnica blossoms should be spread out in a thin layer on racks with good airflow. The temperature should be no higher than 100 degrees F, and blossoms, when possible, should be dried in relative darkness to preserve color. Do not be alarmed if flowers puff out as if going to seed. This fuzzy, seedy look is characteristic of arnica and is not a problem. The trick is to dry the blossoms quickly and completely. Arnica flower blossoms should dry in about three days.
Pests and Diseases
With proper crop rotation and soil maintenance we have seen little to no pest or disease pressure.