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Ginseng Growing
Robert L. Beyfuss, Agriculture and Natural Resources Program Leader, Cornell Cooperative Extension of Greene County, HCR 3, Box 906, Cairo, NY 12413
Abstract: American ginseng (Panax quinquefolium) and goldenseal (Hydrastis canadensis) are herbaceous perennial plants native to North American forests. Both are highly valued as medicinal herbs with a long history of collection from wild populations. Attempts to cultivate these herbs in natural forest environments have met with mixed results due to the exacting site requirements and a general lack of published information regarding cultural practices. Recent investigations of sites harboring wild populations of ginseng in New York, Massachusetts, North Carolina and Tennessee have yielded interesting data regarding the ecological niche of this woodland herb. This new data will be very useful to potential growers of both ginseng and goldenseal since both plants have similar native habitats.
Keywords: ginseng, goldenseal, panax, hydrastis
Introduction: Botanical Features of Ginseng and Goldenseal
Ginseng is the common name for a number of deciduous perennial herbs in the family Araliaceae. Hortus Third (Bailey staff ,1976) describes these members of the genus Panax as "about six species of glabrous herbs with thick roots and simple stems; native to North America and eastern Asia: leaves borne in whorls, palmately compound, leaflets toothed or lobed: flowers small, polygamous in mostly single, terminal umbels, petals five, imbricate, sometimes united, stamens five, ovary 2-3 celled, styles 2-3, separate or in male flowers united; fruit a drupe, pyrenes 2-3."
The common name "ginseng" is derived from two Chinese words meaning "likeness of man" because the mature root of the ginseng plant often resembles a human figure. The scientific name Panax comes from the Greek "pan-axos" meaning "all-healing" (Fulder 1980). Of the three species mentioned in Hortus Third, two of them are native to north America, Panax quinquefolium, which is commonly called American ginseng and Panax trifolius or dwarf ginseng. Only American ginseng is of significant economic interest in the United States.
Goldenseal (Hydrastis canadensis) is generally included in the buttercup family (Ranunculaceae) or sometimes a separate family (Hydrastidaceae) containing one species native to eastern North America. The common name was adopted in the 1880 revision of the United States Pharmacopoeia (Foster 1991). Other common names include yellow root, orange root, ground raspberry and yellow eye. Scars left on the yellow colored rhizome where the stem has senesced resemble wax seals, once used to seal envelopes. Hortus Third describes it as "leaves palmately lobed; flowers small, solitary, sepals 3, petaloid, petals 0, stamens many, clavate; fruit a berry, several in a cluster".
Both ginseng and goldenseal occur in fertile, moist, woodland soils from southern Canada to Georgia, west to Alabama and north to eastern Iowa and Minnesota. Both have evolved as understory plants with very similar habitat preferences and both have long histories of traditional medicinal uses.
Medicinal Uses
Simply and eloquently stated "The worth of all other plants pales in comparison with the value proclaimed for ginseng by millions. Ginseng is the only plant used routinely by so great a number of more or less healthy individuals for stimulation, added energy, and a sense of well being - a panacea for the healthy who want to remain well for a long time and if possible, become healthier." (Lewis 1977) Approximately 4,600 years ago Huang Ti, the first human ruler of China documented ginseng's medicinal properties in the "Nei Ching Su Wen" the Yellow Emperor's Book of Internal Medicine-the first written text of Chinese medicine.
Interestingly, the western world has long been skeptical of ginseng's medicinal properties. The British Pharmacopoeia does not mention it, nor does the British Pharmaceutical Codex (Fulder 1980). In the United States, ginseng was once listed in the U.S. Pharmacopoeia, but was removed from this list in 1880. The U.S. National Formulary (another listing of useful drugs) dropped ginseng in 1937 noting that the extraordinary properties and medicinal virtues formerly ascribed to ginseng had no other existence then in the minds of the Chinese (Fulder 1980).
It is not surprising, therefore, that the beneficial effects of ginseng are not appreciated in the western hemisphere. The prevailing view in the west is that each disease arises from a specific cause and is a discreet entity which can be cured by drugs which are applied for the specific disease. Curing the disease will cure the patient since the patient is merely the carrier of the disease. Much of "modern medicine" is directed at curing disease and not maintaining general health. Ginseng has never been demonstrated to unequivocally cure any specific disease. It is consumed to maintain good health which, in turn, prevents disease from occurring.
The debate regarding the beneficial effects of ginseng has been raging for more then a century and shows no sign of abating in the foreseeable future. Countless papers have been published from nations throughout the world on both sides of the issue. Ginseng roots and dozens of extracts from ginseng roots have been analyzed for "active ingredients" for many years. At least 20 physiologically active compounds dubbed "ginsenocides" are now generally considered to be responsible for some of the beneficial effects of ginseng since they appear to mimic the effects of the whole root when applied individually. Levels of some of these ginsenocides are now being studied in wild and cultivated ginseng roots in laboratories at Cornell University and elsewhere (Fichtner, Mudge 1997, unpublished).
Regardless of efficacy, ginseng use has been increasing dramatically in the west as more and more people look to alternative medicinal products and practices. First person testimonials by celebrities such as nationally syndicated talk show host Larry King have given credence to ginseng and many other alternative medicines. It is unlikely at this time that a "definitive" study will put the issue to rest once and for all. It is perhaps in the best interests of the ginseng growers for the medicinal properties to remain a mystery. Many former botanical medicines such as foxglove (Digitalis sp.) have been abandoned once their active ingredients have been isolated and synthesized.
In contrast, goldenseal, has a number of well documented active ingredients. The major alkaloids include hydrastine (2-4%), berberine (2-3%), and smaller amounts of canadine and hydrastinine (Genest, Hughes 1969). Hydrastine lowers blood pressure and stimulates involuntary muscles while berberine stimulates secretion of bile in humans, is antibacterial and has numerous other activities (Leung 1980).
According to Hobbs (1990) goldenseal is among the top selling herbs in the American health food market and is used as an antiseptic, hemostatic, diuretic, laxative, and tonic for inflammations of the mucous membranes. It has also been recommended for hemorrhoids, nasal congestion, mouth and gum sores, eye afflictions, externally for wounds, sores, acne, ringworm and other ailments (Leung 1980). Tyler (1985) reports that goldenseal was frequently and enthusiastically recommended for the treatment of sore mouth and related problems. A teaspoon of the powdered root, mixed in a glass of water, was recorded as a folk remedy for sore throat and stomach troubles (Foster 1991).
A more modern folk use has been as a means to mask illicit drugs in urine tests although there is no scientific evidence to support this use and it may, in fact, instead promote false-positive readings (Tyler 1987, Foster 1990). This is a much more difficult myth to dispel since testimonials in popular press continue to appear periodically.
Since both ginseng and goldenseal have such long histories of domestic use with few reports of toxicity, other then those based on poor procedures or suspect ingredients, it is safe to say that these roots can be consumed with a reasonable assurance of safety. This is not necessarily the case with some other popular herbs in use today. It is also important to note that there are virtually no guarantees to insure the consumer that he or she is actually buying pure ginseng or goldenseal. The only way to be absolutely certain that the ginseng or goldenseal that you consume is pure is to grow your own.
Historical Aspects of Ginseng and Goldenseal Commerce
American ginseng was "discovered" in North America by a French Jesuit missionary named Father Joseph Francis Lafitau in 1716 near Montreal, Canada (Persons 1986). He had heard of this wondrous plant through the writings of another Jesuit priest, Father Jartoux, who had observed the use of Asian ginseng in Manchuria. Since the forest types and climate of Manchuria and southern Canada were so similar, Father Lafitau hypothesized that ginseng might grow in North America. Soon after its discovery ginseng was being dug by the native North Americans, purchased by French fur traders and exported to China. Even today many fur dealers in New York and elsewhere are also ginseng dealers. Ginseng and furs were the new world's very first exports.
Ginseng was discovered in western New England in 1750 and in 1751 in central New York, Massachusetts and Vermont. John Jacob Astor of the American Fur Company financed one of the first American shipments to China in the late 1700's and it has been widely reported that ginseng started the Astor fortune (Persons 1986). Daniel Boone gathered and purchased for export twelve tons of ginseng in 1788 in Kentucky. In 1858, 366,053 pounds of ginseng was exported according to the United States Department of Commerce and Labor (Harding 1972). Between 1858 and 1901 ginseng exports averaged 278,000 pounds per year. Prices paid for the dried roots during this time ranged from 52 cents per pound in 1858 to $5.38 per pound in 1901 with an average price of $2.50 (Harding 1913). During this time period almost all ginseng was gathered from wild populations. Obviously, this situation would not last indefinitely.
In the early 1880's a New York State Ginseng Association was formed with George Stanton serving as President. Mr. Stanton is now widely recognized as the Father of the Cultivated Ginseng Industry (Williams 1957). In 1904 Liberty Hyde Bailey, then director of the Cornell University Agricultural Experiment Station wrote "New York is one of the leading states in the growing of ginseng. Considering the value of the New York product and the attention given to the plant, it is not improbable that New York leads the states" (Van Hook 1904).
Ginseng farming became quite common throughout much of its native range at the turn of the 20th century as the supplies of wild roots disappeared due to over-harvesting. Between 1906 and 1970 ginseng exports averaged 215,000 pounds per year (Harding 1972) with only one year showing a significant decline (1951) due, most likely, to the Korean war. Even that year exports still amounted to 77,000 pounds.
In 1977 the U.S. Fish and Wildlife Service began to implement the internationally approved CITES treaty. CITES stands for the Convention on International Trade in Endangered Species which lists ginseng as one of many plant and animal species that need protection. (Persons 1986) Ginseng now needs to be certified as to whether it is wild or cultivated and states must adopt a conservation program to allow any harvest of the wild roots. Nineteen states now certify all ginseng exports as to wild or cultivated. Between 1988 and 1993 the average certified export of wild ginseng amounted to 158,000 pounds per year nationally with Kentucky and Tennessee leading the states averaging 23,666 and 17,833 pounds respectively. During that same period of time exports of cultivated ginseng averaged 1,341,000 pounds per year, however, the overwhelming majority of the cultivated crop came from one state, Wisconsin, which averaged 1,317,000 pounds. Almost al of the cultivated Wisconsin ginseng grown under artificial shade (Pritts 1995).
In recent years significant increases of cultivated ginseng grown under artificial shade have occurred primarily in British Columbia and Ontario, Canada. Ontario alone in 1997 reported more then 2,000 acres and British Columbia has close to 1,000 acres. With an average yield of 2,000 pounds per acre, an additional 6 million pounds per year are being harvested in North America since the late 1980's. China is also becoming a major producer of American ginseng with at least 250 acres in production in 1987 (Proctor 1987) and, most likely, much more by 1997.
The effect of this huge increase in supply has had a predictable effect of the price of cultivated ginseng. During the mid 1980's Wisconsin ginseng farmers were receiving between $40 and $60 per pound depending on quality. By 1997 prices had dropped to $10 to $15 per pound.
It is interesting to note that while the price paid for field cultivated ginseng has dropped dramatically in the past 10 years, the price for wild or woods cultivated ginseng has risen just as dramatically. In 1985 wild ginseng in New York state sold for approximately $180 per pound . In 1995 the price was $500 per pound and in 1997 the average price was in the range of $300 to $400 per pound.
In summary, it is safe to say that the price curve for ginseng since the 1800's resembles a roller coaster, reflecting not only supply and demand but many other factors, not well understood.
Goldenseal also has a long history of collection and exploitation. As early as 1884 and 1885 Lloyd and Lloyd noted dramatic declines in wild populations, partially due to over-harvest, but also due to loss of woodland habitat (Foster 1991). In 1904 prices ranged from 74 cents to $1.50 (Harding 1972). Harvest data is generally unavailable from the early years but Harding (1910) quotes "reliable dealers" as estimating the harvest at between 200,000 and 300,000 pounds per year with less then 10% being exported. Foster (1991) reports "there are no figures to determine current supply and consumption of Goldenseal. However, supply shortages and gluts with their attendant price fluctuations have been experienced in the past decade, just as they were 100 years ago."
It is interesting to note that goldenseal was used by many tribes of eastern native Americans far more then ginseng for many different maladies and was considered a much more useful plant. On the other side of the world ginseng was, and still is, considered the "King of Herbs". This important distinction is responsible for the continuing large demand for high quality ginseng while goldenseal, despite it's known pharmacological properties, does not command similar interest.
How to Grow Ginseng and Goldenseal in Your Forest
Both ginseng and goldenseal thrive in rich, moist, forest soils that are high in organic matter. Both require 70 to 85% shade and are found as companions to mature, deep rooted trees in the wild. Other herbaceous plants which grow in similar environments include maidenhair fern
(Adiantum pedatum), Christmas fern (Polystichum acrosstichoides), Jack-in-the-pulpit (Arisaema triphyllum), Blue Cohosh (Caulophyllum thalictroides), and Baneberry (Actea pachypodia). The tree species most commonly associated with ginseng in the northern part of its range is sugar maple (Acer saccharinum). In the southern part of it's range it is often associated with tulip poplar (Liriodendron tulipifera). A study of ginseng habitat in Western North Carolina and East Tennessee by Jim Corbin (1997) listed the following plants, in addition to many of those listed above, as appearing between 99 and 100% of the time in good ginseng stands, Dutchman's Pipe (Aristolochia macrophylla), Black Cohosh (Cimicifuga racemosa), Spicebush (Lindera benzoin) and Silverbell (Halesia carolina) as well as a few other more cosmopolitan species that occur in many varied environments.
Appropriate site selection is extremely important for ginseng and goldenseal production. Although both species may be cultivated in other habitat types and even in artificially shaded, intensively managed fields, success is much more easily achieved in environments which resemble the natural state of both species.
There is a major distinction between ginseng and goldenseal as to the final product that is produced and how it is produced. The age and appearance of ginseng roots have a dramatic effect on the market value. In general, the older the roots are, the more valuable whereas with goldenseal, age and appearance are not nearly as critical. Prices paid per pound of dried ginseng root range from $10 to $500 with the highest prices paid for the oldest, best looking root and the lowest prices for three to four year old root, grown in fields under artificial shade. Goldenseal is generally dug at five to six years of age when it reaches its maximum size and the appearance of the root does not matter. The price paid for goldenseal root is much more dependent upon supply and demand in any given year then appearance.
Site preparation varies with type of growing operation ranging from wild simulated to intensively managed raised beds. Wild simulated usually requires no more site preparation that raking back the existing leaves and duff, broadcasting seed and allowing nature to take it's course. Ginseng grown in such a manner for a period of 10 years or more usually commands the same price as truly "wild" ginseng. This type of cultivation is only possible in the most appropriate sites which have soils of medium to high fertility, well supplied with calcium, an absence of pests and ample moisture availability.
Most growers will usually do some site preparation prior to planting either seeds or small roots. Once a site is located, competing vegetation is removed either by hand or by the use of a non-selective herbicide. Small, pole sized trees are usually removed as is all woody brush. When possible the soil is roto-tilled several times and larger rocks are removed. The main objective in site preparation is to create a site that will facilitate maintenance and eventually root harvest. Raised beds look nice and may enhance drainage slightly but will not substitute for a naturally well drained site which is a crucial requirement.
The issue of whether or not to fertilize prior to planting, and if so, how much, and what type, is a continuing source of debate for both ginseng and goldenseal. Dr. Jeanine Davis at North Carolina State University writing about goldenseal advises taking a soil test and following recommendations for native ornamentals using organic sources of nutrients such as composted manure, composted leaves, bone meal or cottonseed meal being careful not to over-fertilize. There are no recommendations for soil pH although many growers adjust the pH to between 6 and 7 (Davis 1994).
Ginseng fertilization is even more of a mystery. In controlled experiments it has been demonstrated that ginseng roots do grow larger and faster when fertilized (Konsler 1980) however, there is a concern that fertilizer may encourage disease development. Many growers report serious increases in disease outbreaks in healthy stands only after fertilizer and /or garden limestone has been applied. Unpublished data by the author indicates that healthy stands of wild ginseng in NY State, Massachusetts and West Virginia are found in soils with wide ranges of nutrient availability and wide ranges of ambient pH from 3.9 to 7.0. The one element that consistently appears at higher then expected levels is calcium (Corbin 1997). Stoltz found that calcium deficiency resulted in a rotting of the primary root (1982). Konsler (1982) obtained increased root weight when he used calcium nitrate as a nitrogen source, but reduced root weight when he used urea. Tissue samples from ginseng and companion species reveal high calcium levels in good stands of wild ginseng (Corbin 1997). Observations by Corbin and Beyfuss indicate that substantial addition's of gypsum (calcium sulfate) at rates of up to 4,000 pounds per acre produce much larger roots then controls.
Planting Procedures
Both ginseng and goldenseal may be propagated by planting seeds or rootlets. Goldenseal may also be propagated from rhizome pieces or rootlet cuttings. Ginseng rootlets are usually planted whole. The most economical way to plant ginseng is from seed. Ginseng seed has a very complicated dormancy mechanism. Ginseng berries appear on three year old and older plants. The berries ripen from late July until mid September depending upon geographic location, weather and other factors. Within each ginseng berry are one, two or three seeds. Almost all of the seeds have an immature embryo which continues to grow well into the fall and early winter. The majority of the seeds will not germinate until two winters have passed. Thus, most of the seed within berries which ripen in August of 1997 will not germinate until spring of 1999. The seed is highly perishable and subject to desiccation, consequently most ginseng seed is planted in the fall prior to spring emergence, approximately one year after harvest. Ginseng seed that remains in the stratification box until spring often germinates prematurely, even at temperatures as low as 34 degrees F. Seed which has already sprouted usually perishes unless planted almost immediately.
Ginseng seed are either planted approximately one inch apart in rows six inches away from each other or broadcast at the rate of 6 to 12 seeds per square foot. There are between 6 and 8 thousand seeds per pound. Most growers purchase stratified seed. Seeds are planted one half to one inch deep and mulched immediately after planting with up to two inches of shredded leaves or clean straw. Wild simulated plantings are usually just covered with nearby leaf mold after broadcasting.
One, two and three year old rootlets are sometimes planted to save time and to establish seed bearing plants sooner. Rootlets are planted almost horizontally with the apical bud facing uphill if possible. The apical bud is usually fully developed by early August and rootlets may be dug and transplanted anytime after the bud is fully formed.
Ginseng plants tend to be self thinning if planted too densely. Seedlings can be grown at a density of 10 or 12 per square foot, hand thinned to approximately 6 per square feet after the first growing season and thinned again after the second year to a final density of 1 or 2 plants per square foot. This wide spacing helps to prevent rapid spread of foliar or root diseases. Crowded ginseng plants are almost always troubled by disease. Field grown ginseng is planted at rates as high as 25 plants per square foot and requires frequent applications of pesticides to control diseases.
Goldenseal seed is also planted in the fall but rootlets, rhizomes and root cuttings may be successfully planted in the spring also (Davis 1995). Plants started from seed usually flower in their third or fourth year of growth although vegetatively propagated plants may flower the year they are planted. Seed are planted at the rate of 3-4 seeds per foot in rows six inches apart with seeds one half inch deep. Seedbeds are covered with 2 to 3 inches of straw or some other sort of organic mulch.
Pests of Ginseng and Goldenseal
In their wild state both ginseng and goldenseal do not seem to be plagued by many pests. When cultivated however, both have serious problems from diseases and other pests. The most serious pest of both are slugs which can eat the seed, the seedling or even entire older plants. Slugs are controlled by hand picking, trapping or the use of commercial slug poisons. Regulations regarding the use of pesticides vary a great deal from state to state. Growers are advised to become familiar with all pertinent regulations before applying any pesticides to either crop.
Perhaps the second biggest pest problem associated with these crops is thievery. Poachers may visit ginseng or goldenseal plantings and simply help themselves when the owner is not around. Growers are advised to investigate security issues before planting.
Ginseng and goldenseal are also attacked by fungal diseases. The most serious diseases of ginseng are leaf and stem blight caused by Alternaria panax and root rot caused byPhytophthora cactorum. Both diseases are controlled somewhat by commercial fungicides where legal. Both diseases may be seed borne so careful selection of seed sources is important. Goldenseal is subject to a leaf blight caused by a species of Botrytis.
Mice, chipmunks, gray and red squirrels will readily eat ginseng berries and seed, often before the berries even begin to ripen. Wild turkeys, ruffed grouse and songbirds may also eat berries in the forest. White tailed deer may occasionally eat foliage but ginseng is not a preferred deer food.
In addition to the two diseases mentioned above ginseng is also attacked by several other fungi and at least three species of insects. Once again it must be stated that prospective growers should become familiar with the rules and regulations regarding pesticide use before applying or even before planting.
Goldenseal does not appear to be afflicted by nearly as many problems as ginseng and in this regard, may be planted in some locations where ginseng has perished due to root rot. Both species will have far fewer problems of any sort if planted in appropriate locations using seed that is derived from healthy sources.
Ginseng and Goldenseal Harvest
Goldenseal is usually harvested about three to four years after planting when the plants fully occupy the area they were planted in. It does not pay to wait longer as the oldest roots start to die off when the planting becomes crowded. Roots are generally dug in the fall after the tops have died down unless a market can be found for the leaves and stems. It is important to dig carefully so as not to injure the many fibrous roots. Pieces of roots with buds that are destined for replanting should be kept moist and cool or replanted immediately. Roots to be sold are spread on screens and gently hosed down to remove all surface soil. Cleaned roots are spread on screens again and dried in the shade or in a forced air drier. The roots will loose about 70% of their weight during the drying process. Dried roots should be packed loosely into boxes and stored in a cool, dry environment. Yields of goldenseal have been reported at 1,000 to 2,000 pounds per acre under excellent growing conditions.
Forest grown ginseng is usually left to grow for at least 7 years or longer. As mentioned above, the older the roots are, the more valuable. Like goldenseal, they are dug in the fall, being careful not to injure the hair-like fibrous roots. Roots are dried using the same procedure as outlined above for goldenseal. Ginseng also looses about 70% of it's fresh weight during the drying process.
Marketing Ginseng and Goldenseal
Virtually every state that harbors populations of wild goldenseal and wild ginseng has buyers who routinely place advertisements during the fall in local, rural newspapers offering to buy. Many states including NY, Wisconsin and Maine have grower's organizations which can help to market roots. Local fur buyers or trappers also are often buyers of ginseng or goldenseal. The local or state conservation or agriculture agencies may also be able to assist with marketing. Cooperative Extension Services may also be consulted for information regarding growing and marketing of both ginseng and goldenseal.
Costs and Returns
It is very, very difficult to accurately project costs and returns of any ginseng or goldenseal enterprise due to the wide range of prices paid for the final product as well as the constantly changing costs of inputs. For example, in 1997 stratified ginseng seed was sold in NY State for prices ranging from $30 to $200 per pound depending upon seed origin, quantity purchased and other factors. Dried ginseng root grown in NY state sold for prices ranging from $40 per pound to $400 per pound, again depending upon age of the roots and quality. Costs of establishing and maintaining gardens vary from region to region, state to state and even within the same county. Local property taxes, prices paid for timber, real estate values and other variables all need to be considered before undertaking a ginseng or goldenseal growing venture.
References
Bailey Hortorium Staff, 1976. "Hortus Third". Macmillan, N.Y.
Foster, S., 1991 "Goldenseal, Hydrastis canadensis, Botanical Series No. 309, American Botanical Council, Austin TX
Fulder, S. 1980 "The Tao of Medicine" Destiny Books, NY, NY
Lewis, W. 1977 "Medical Botany-Plants Affecting Man's Health". John Wiley & Sons NY, NY
Fichtner, E. and Mudge K. 1997 " Comparison of Extraction, Purification and Analysis Methods of Ginsenocides from American Ginseng" Cornell University, Ithaca NY
Genest, K. and Hughes, D.W. 1969 "Natural Products in Canadian Pharmaceuticals IVHydrastis canadensis. Canadian Journal of Pharm. Science
Leung, A.Y. 1980 "Encyclopedia of Common Natural Ingredients Used in Foods, Drugs and Cosmetics. John Wiley and Sons NY, NY
Hobbs, C. 1990. "Goldenseal in Early American Botany". Pharmacy in History vol.32
Tyler, V.E. 1987 "The New Honest Herbal" George F. Stickley Company. Philadelphia, PA
Persons, W.S. 1986 "American Ginseng Green Gold" Bright Mountain Books Inc. Asheville, NC
Harding, A.R. 1972 " Ginseng and Other Medicinal Plants" A.R. Harding. Columbus, OH
Williams, L.O. 1957 "Ginseng" Economic Botany. 2 (4) : 347.
Van Hook, J. 1904 "Diseases of Ginseng" Cornell U. Ag. Ex. Sta. Bulletin 219
Pritts, K.D. 1995 "Ginseng: How to Find, Grow, and Use America's Forest Gold" Stackpole Books. Mechanicsburg, PA
Proctor, J.T. 1988 "East Meets West: Cultivation of American Ginseng in China" HortScience, Vol.23 (6).
Corbin, J. 1997 "A Study of American Ginseng Habitat in Western North Carolina and East Tennessee" (unpublished)
Davis, J.M. 1994 (?) "Advances in Goldenseal Cultivation" North Carolina State University, Mt. Hort. Crops. Research and Ext. Center, Fletcher NC
Stoltz, L. 1982 "Leaf Symptoms, Yield and Composition of Mineral Deficient American Ginseng" HortScience, 17 (5)