Arnica (Arnica montana)

How well established is this crop?

This is a very new crop to the Otago region. The plants should grow but information on markets, commercial returns, current growers, and any form of regional research may be difficult to find.

Background

Arnica is a medicinal herb with known anti-inflammatory, analgesic and antiseptic effects. These effects are due to a chemical group known as sesquiterpene lactones, present in the flowers. Arnica is a member of the daisy family, native to the meadows and mountainous regions of Europe. Arnica grows naturally between 500 and 2500 m altitude on acid soils of low fertility. Arnica is the only medicinal herb being actively sought by processing companies, keen to offer growers supply contracts to grow the crop. Over-harvesting of the wild populations of arnica have led to it being protected at a time when worldwide consumption of products is going up.

Climate

Research data in New Zealand shows that arnica does best in a cool moist growing environment. Places such as coastal Otago and Southland provide ideal locations. When grown in these areas the plants get sufficient winter chilling to initiate flowering, flower yields are greater, and disease problems appear to be less than more northern regions.

Winter Chilling and Frosts

Even though it is from mountainous areas of Europe it is expected that the hard frosts of a Central Otago winter will damage the crop. In the coastal areas it gets enough chilling to set flowers the following season. Arnica does not seem to flower anywhere north of Christchurch.

Rainfall and Irrigation

Care needs to be taken with irrigation due to the plants susceptibility to fungal diseases. Arnica does not seem to be affected by rainfall at any stage of its growth. However they also do not like drying out. Have prospective irrigation water tested and ensure it is not too high in soluble salts, as these have been seen to result in high levels of plant death.

Wind

Shelter from the wind is advisable, even though arnica is a low growing plant. It will reduce the amount of damage to the plants and subsequent disease problems.A good rule of thumb when designing shelter is to multiply the final height of the shelter by 5. Use that measurement as the distance you position your shelters apart. For example, when using shelter trees that are 10m high you will need shelters 10m x 5 = every 50m. Some consultants are recommending a multiplier of 10 for crops, but with a valuable plant such as this a more conservative approach is advised.

Soil

The key physical requirement of the soil for arnica growing is a free draining root zone. This will ensure the roots and crown are not always wet, which can lead to fungal diseases.

Fertility

Arnica grows naturally in the high mountain pastures. These areas tend to be highly leached of nutrients. As a consequence you need to be very careful with fertilisers around this plant. Even low levels of soluble salts can kill them. Low fertility soil appears the best.

Weed Control

Arnica is a slow growing perennial. It does not compete well for space, especially against aggressive plants, such as white clover. This is going to be the key problem with any organic production system.

Varieties

There are two types of arnica, Arnica montana and Arnica chamonensis. Only A. montana has the medicinal herb properties. A. chamonensis looks similar, but has smaller flowers.

Pests and Diseases

Growing arnica can be very challenging as the plants are susceptible to a range of fungal diseases, especially around the crown. Ensuring the soils are free draining and using regular applications of fungicides will minimise these risks.

Slugs and snails are the main insect pests that attack the plants and eat the foliage. Trial work is currently looking at the best way of controlling this problem.

Layout

Plants need to be spaced about 25-30cm apart. This leads to a density of 16 per square metre. Access is needed down each side of the rows for harvesting and weed control. Rows can be as long as is practical.

General Management

The crop is not easy to grow. Seed germination is erratic and the plant competes poorly against perennial weeds such as Californian thistle, couch and white clover. Under adverse soil conditions (very wet or very dry) and high temperatures the plants die rapidly with fungal invasion. However, under good management an Arnica crop can be expected to have an economic life of four seasons.

Harvest

The current method of harvesting is to pick the flowers by hand. The highest levels of sesquiterpene lactones are obtained just after the flower petals begin to senesce, but before the petals drop entirely from the head. Gloves that go right up the arm of the picker are required, as some people have an allergic reaction to the plant. Flowers can be picked into bins, cooled and taken to a drying plant. When drying the flowers the temperature is not raised much past 40C. Instead the drying process relies on airflow. Any hotter than this, and the level of active ingredient in the plant is reduced.

Equipment

Most of the work on current plantings of arnica is done by hand. A tractor will be needed to form the raised beds but after that most of the work can be done with common gardening tools such as hoes and a knapsack sprayer. At harvest you will need bins to pick the flowers into and then access to a suitable drier. A cooperative approach to this aspect of production is recommended.

As plantings of this crop increase, more research work will be done on mechanical harvesting. Mechanical harvesting is not used at present because flower maturity varies so much, so development of a mechanical harvesting programme needs to hand in hand with a breeding programme that will produce plants that all flower at the same time.

Returns

Arnica has been grown successfully in a number of locations in the southern South Island but only one large scale planting has been grown so far. This was at Invermay Research Station near Mosgiel. From this trial dried flower weights of 230 kg/ha were recorded in the first year and 560 kg/ha in the second year. Contracts to supply Arnica are currently being offered by New Zealand based medicinal herb processors. Prices are in the $60/kg range for dried flowers. 5-6kg of fresh flowers are required to produce 1kg of dried.

Contacts

For technical and financial information about Arnica contact:
Bruce Smallfield
smallfieldb@crop.cri.nz
03 489 0162

A company looking to buy Arnica is based in Havelock North contact:
Andy Black
Weleda Medicine and Bodycare
0800 802 174
andy@weleda.co.nz