Licorice

Glycyrrhiza glabra and Glycyrrhiza uralensis

 

The earliest use of Licorice was recorded in 2100 B.C.,and Glycyrrhiza is a Greek word meaning “sweet root.”   In Chinese traditional medicine, licorice is the most used herb after Ginseng.  The compound, glycyrrhizin, is responsible for the sweet flavor of licorice roots.  The herb has uses ranging from as a cough suppressant to an anti-inflammatory for ulcers.  It also stimulates the adrenal glands, and in Chinese medicine is often used to “balance” other herbs in a prescription.  People at risk for high blood pressure should not use licorice, however.  Most “licorice” candy is now flavored with anise, not G. glabra, though the herb is still used to flavor tobacco products.

 

Family:  Pea/Legume
Life cycle:  Perennial (Zone 6-11 for G. glabra, 4-11 for G. uralensis?)
Native:  G. glabra is native to SW Asia and the Mediterranean region, cultivated in Europe since at least the 16th century, while G. uralensis is native to central Asia, China and Japan.  A third species, G. lepidota, is native to North America, found mostly in the Great Plains and west.
Height: 
2-5 feet
Sun: 
Full sun to partial shade.
Soil: 
Well drained soil, seems to prefer a pH of 6.5 to 8.
Water: 
Moderate
Flowers: 
Flowers bloom in mid-late summer, lavender and white flowers.  However, we rarely observed G. glabra or G. uralensis blooming in our field plots here in Kansas.
Propagation: 
Seed must be stratified for several weeks, and  must be scarified and soaked for 2 hours in warm water  before  sowing.  Treated seed will germinate at a rate of about 80 percent compared to untreated seed at 20 percent germination rate.  Germination takes about 2 weeks. Direct planting in the field can be done but the germination rate is about 20 percent.  Space 2 feet apart,  plant will spread.  Possible to plant from rhizome cuttings also.  This plant will re-sprout from harvested roots/rhizomes, so don’t plant it in a spot unless you are prepared to have it there more or less forever.
Harvesting: 
Harvest roots in the 2nd or 3rd year using a needle nose spade or other digging tool.  Harvest in the spring or fall.  The plant will form a sturdy taproot, several branch roots, and also send out runners up to 8 meters (26 feet) long.
Parts used: 
Rhizome/root, fresh or dried.
Used as: 
Decoction, tincture, syrup elixir, lozenge, medicinal food, fluid extract, tonic
wine.

Medicinal benefits: 
In Europe, G. glabra is approved for use by physicians for cough/bronchitis, and gastritus.  In laboratory studies, licorice has demonstrated anti-inflammatory effects, and is protective against gastric ulcers.  It also has anti-viral and anti-fungal effects, but can increase the retention of water, and induce high blood pressure.  Common folk uses include winter tonic for immune, digestive tract, respiratory tract, and adrenal gland support.  Native Americans have used G. lepidota root tea to reduce fevers in children, and a poultice of the leaves to treat earaches.  Some would also chew the root to keep the mouth moist, and to strengthen the throat for singing.
Market potential: 
High.  Buyers need good organic sources for this herb.  Much of the G. glabra is now imported from Europe and the G. uralensis is imported from Asia.  Domestic, organic sources should be popular.  G. glabra root sells for $3.35 - $25.60/lb dw, and G. uralensis sells for $18.20 - $46.40/lb dw.

 

KSU Field Trial Data - 2000-2002.  

GLYCYRRHIZA GLABRA

 

 

 

 

 

 

1st Year

2nd Year

3rd Year

Average

Comments

 

 

 

 

 

 

Location/Years

5

3

2

 

 

Survival (%)

85.2

171.7

126.0

127.6

Survival numbers higher than 100% indicate that the plant was spreading via rhizomes.

Vigor (rating)

3.6

3.9

3.7

3.7

 

Height (cm)

38.4

54.7

75.5

56.2

 

DW Herb (g/plant)

12.1

46.0

49.9

 

 

DW Root (g/plant)

8.7

53.2

50.8

 

These roots appear to be less affected by the drought in 2002 than the G. uralensis (see next table)

Maturity (rating)

1.0

1.3

1.0

1.1

Observed blooms in late summer of 2001 only.

Insect (rating)

0.5

0.5

0.5

0.5

 

Disease (rating)

0.1

1.5

0.6

0.7

 

 

 

 

 

 

 

Est. planting density

21,780

21,780

21,780

 

Assume 1’ x 2’ spacing

Plant density x survival.

--

21,780

27,443

 

Assumed 100% survival in 2nd yr, then 126% in 2nd year. 

kg/acre DW (g/plant x # of plants - roots)

--

1159

1394

 

 

Est. Marketable Yld

(DW lb/acre roots)

--

2552

3071

 

Root biomass of 5000 lb/A has been estimated by Tim Blakely.  This might be possible if a larger areas was harvested.  For data purposes, we only harvested the root and rhizome attached to one plant, without extracting all the rhizomes that had spread.

Yld x ½ of “low” price

--

$4287

$5159

 

 

Yld x ½ of “high” price

--

$32,666

$39,309

 

 

 

 

 

 

 

 

 

 

GLYCYRRHIZA URALENSIS

 

 

 

 

 

 

1st Year

2nd Year

3rd Year

Average

Comments

 

 

 

 

 

 

Location/Years

2

2

2

 

 

Survival (%)

72.5

69.0

158.0

98.8

 

Vigor (rating)

3.5

4.0

3.8

3.8

 

Height (cm)

30.5

53.0

60.0

47.8

 

DW Herb (g/plant)

6.8

64.0

28.2

 

 

DW Root (g/plant)

4.6

41.8

20.5

 

Yields probably lower in 3rd year due to drought effect on crop, and also difficulty in digging the root from a very dry soil.

Maturity (rating)

1.0

1.0

1.0

1.0

 

Insect (rating)

0.6

0.8

0.7

0.7

 

Disease (rating)

0.2

1.3

0.5

0.7

 

 

 

 

 

 

 

Est. planting density

21,780

21,780

21,780

 

Assume 1’ x 2’ spacing

Plant density x survival.

--

15,028

34,412

 

 

kg/acre DW (g/plant x # of plants - roots)

--

628

705

 

 

Est. Marketable Yld

(DW lb/acre roots)

--

1384

1554

 

The dry weight harvest of this species appears to be lower than that of G. glabra, even when taking the higher plant density in year 3 into account.  Higher “high-end” prices could make up for the lower yields, if they are obtained in the market.

Yld x ½ of “low” price

--

$12,594

$14,140

 

 

Yld x ½ of “high” price

--

$32,109

$36,053

 

 

 

 

 

 

 

 

 

Summary of field trial data:  Neither species seemed to be affected by insects or disease pressure, and at the time of harvest, early fall, both were primarily in the vegetative stage (see maturity rating of 1.0 to 1.1, or vegetative).   If the plants had flowered at all, there didn’t appear to be any seed set or flowers left by late Aug./early Sept.  Both plants spread prolifically, G. glabra by the 2nd year (“survival” rating of 171%!) and by the 3rd year, the survival rating of G. uralensis was 158%.  These numbers were obtained by taking the number of plants observed at the time of data collection divided by the number of plants transplanted in year one, minus those harvested for data the year before.  We also observed many licorice plants of both species in neighboring rows of plots, not simply a few inches or a foot away, but commonly 3 to 6 or more feet away from the original planting.  Both species appear to be winter hardy in Kansas, though one reference claimed that G. glabra was only hardy to zone 9.  Most of Kansas is in zones 5 and 6. 

The main difficulty in growing and harvesting licorice might be in successfully and easily digging and washing roots and rhizomes.  Both can be dug and sold, though the tap root can be pretty firmly rooted, and difficult to get out of the ground.  Some of the rhizomes are easy to pull up by hand, as they will run for several feet, just a few inches above the ground.  This makes harvest largely a hand-labor task, and we aren’t sure whether the economics justify the hand harvesting.  As another side note, the G. glabra that we have grown so far does not have a particularly sweet root, especially as compared to G. uralensis,  and is even a bit bitter tasting, so one might want to check the biotype, or find a superior biotype before planting a whole field to this crop.  Also, once you plant, it will probably be there forever.  This advice would go for flower gardens too.  However, it isn’t like mint, that takes over absolutely everything.  It will spread out its somewhat airy looking fronds throughout the bed every one to three feet, and be a pretty, if un-predictable crop in the flower garden. 

We’ve begun trials with G. lepidota in the field, but don’t have multiple years of data yet to report.  So far, it also appears to be doing well, but we haven’t found any retail prices for this herb, so specialized contracts may be required to sell it.