Licorice (Glycyrrhiza spp)

How well established is this crop?

Initial trial plantings of these crops may have been done. There is little information on plant suitability to the region and no current information on markets, commercial returns or current research. This is a new crop.

Background

Licorice has been used as a medicinal plant in a wide variety of ancient cultures in China, India, Greece and Rome. The plant is grown for the roots which are harvested and then shredded before boiling to produce a black licorice extract. This extract usually contains 6-8% glycyrrizin which is up to 50 times sweeter than sugar, as well as other products that have medicinal properties. In the medicinal herb industry this extract is known as radix glycyrrhizae. Licorice is also grown for flavourings in the confectionary industry.

There are around 12 species of licorice, but only two of these are commercially grown. These are the European licorice (Glycyrrhiza glabra) and the Chinese licorice (Glycyrrhiza uralensis). These plants are a perennial woody herb reaching around 1.5m across after 3-4 years of growth. The plant is frost tender and dies down in the winter before re-emerging in the spring.

Winter Chilling and Frosts

Licorice over-winters as a root beneath the soil surface. Successful trials growing this crop have been carried out in Central Otago, Southland, Canterbury and the Hawkes Bay. Based on this it is expected that it will grow successfully in most other parts of Otago.

Rainfall and Irrigation

Supplementary irrigation near planting is advised in dry areas such as Central Otago even though the plant is said to be drought tolerant. When established, it is expected to require little irrigation.

Wind

Licorice is grown on a paddock scale and shelter from the wind is less important.

Soil

The key physical requirement of the soil for licorice growing is a free draining root zone with a high sand content. This makes harvesting the root much easier than if grown in a clay soil. Free draining soil also reduces the incidence of root diseases such as Phoma.

Fertility

Overseas experience suggests that licorice requires moderate levels of soil fertility. Aiming for a pH of over 6.0 is advisable. The addition of lime will help with this if the soil is too acidic.

Weed Control

Licorice plants will be in the ground for at least 3 years so control of perennial weeds such as thistles is essential before planting. When actively growing, the plants form a dense matt generally suppressing weed growth. However, the problem times for weeds are at the beginning and end of the season.

Because this is such a new crop in New Zealand no herbicides are registered for use. If you use them for weed control it is at the grower's own risk.

Varieties

Only two of the 12 species are commercially grown for the medicinal herb industry. These are the European licorice (Glycyrrhiza glabra) and the Chinese licorice (Glycyrrhiza uralensis).

Pests and Diseases

Trials both overseas and in New Zealand suggest that licorice is relatively free of pests and disease. However, watch for root disease if growing this crop in a wetter site.

Layout

There is no defined layout when growing licorice. Plant spacing can vary between 25cm and 1m apart. Thinking about how the crop will be harvested may be the best way to work this out.

General Management

After planting it’s 3-4 seasons before harvest. As the plants appear to suffer from no pests or diseases, weeding is the only major work that needs to be done. Working on suitable herbicide sprays with ‘off label’ use may also be worthwhile. If not, then hand weeding will be your only option.

Harvest

Using a modified potato harvester may be the best method. This will allow the roots to be removed from the top 30cm of the soil. The roots that are left behind after harvest regenerate, providing the seed stock for the next crop. The one problem with this however is the potential for this plant to become a serious weed. Smaller blocks could be hand dug if the soil conditions allow.

After harvesting the roots can be dried whole, chipped or shredded before sale. The next stage of the processing is to obtain the extract. This is done using hot water and evaporators.

Equipment

Equipment needs will depend on the size of the block being planted. If planted on a commercial scale access to a tractor and harvester will be required in the future. If growing a smaller block then start with a rake and some seed or rhizomes

Processing requires some specialist equipment including low temperature driers, special hot water extractors and evaporators.

Returns

Because no-one in New Zealand has grown a commercial crop of Licorice it is impossible to say what the returns will be.

World production ranges between 30-40,000 tonnes per annum so there must be a place for New Zealand growers to produce this crop. Concentrating on extract production for medicinal niche markets may be a better way to succeed, rather than looking at the lower value confectionary industry.

Contacts

If you are thinking of growing licorice contact Crops and Food Research and obtain Broadsheet 121 or click on the link below.

http://www.crop.cri.nz/home/products-services/publications/broadsheets/121-Licorice.pdf