1. Ginseng is a long-lived herbaceous perennial of the Araliaceae family. The species has a slow growth rate, a long pre-reproductive period (ca. 3–8 years), low fecundity, and high seed and seedling mortality (Carpenter and Cottam 1982; Lewis and Zenger 1982, 1983; Schlessman 1985; Charron and Gagnon 1991; Anderson et al. 1993; Dunwiddie and Anderson 1999; Schluter and Punja 2000).
2. Ginseng forms a special underground stem, known as a vertical rhizome, that sits on top of the main root and from which grows the single above-ground stem. The rhizome is characterized by alternating bud-scale scars that form as a result of the annual loss of the aerial stem. These annual stem scars can be counted to determine the approximate age of the plant (Lewis and Zenger 1982; Anderson et al. 1993; McGraw, unpublished data, 2005; Persons and Davis 2005; Kauffman 2006). The location where the rhizome and the root collar meet marks the first year’s growth, and each subsequent year’s growth is marked by a bud-scale scar (Carpenter and Cottam 1982; Lewis and Zenger 1982; Anderson et al. 1984, 1993, and 2002). Hence, the minimum age of a plant (root) can be determined as the number of bud-scale scars plus one. However, the chronological age of a plant may be greater because no scar forms in years when plants remain dormant (see below). It may also be difficult to count the exact number of bud-scale scars on some roots.
3. Reproduction is by seed. Although anecdotal information suggests that ginseng can regenerate by planting the rhizome of a plant, vegetative (asexual) propagation by rhizome or root fragmentation has been rarely observed to occur naturally in the wild (Lewis and Zenger 1982; Lewis 1988; Charron and Gagnon 1991). According to Burkhart and Jacobson (2004) this method of propagation is often less reliable than planting seeds.
A limited field experiment indicated that intact rhizomes were capable of regenerating when planted. However, only 13% of the rhizome propagules were successful compared to 49% of the whole roots and root propagules planted (Van der Voort et al. 2003).
4. Ginseng has been typically grouped into four morphological classes (referred to as size- or stage-classes) based on the number of leaves, commonly referred to as “prongs.” These classes are the following: 1-leafed, 2-leafed, 3-leafed, and 4-leafed plants. Although ginseng plants can produce up to 5 leaves, such plants are rarely encountered in the wild. Ginseng size-classes can be used to broadly estimate the age-class of individual plants and are a good indicator of root size (Lewis and Zenger 1982; Charron and Gagnon 1991; Anderson et al. 1993).
5. However, growth rate varies among individual plants due to biotic and abiotic factors (e.g., genetics, habitat quality, and environmental conditions), so plants with the same numbers of leaves and leaflets may be close in size, but not identical in age (Carpenter and Cottam 1982; Lewis and Zenger 1982; Anderson et al. 1983, 1993; Anderson 2002; McGraw, in litt. 2005). Field studies have shown that 3- and 4-leafed plants can subsequently regress in numbers of leaves the following year (e.g., 4-leafed plants to 3-leafed plants, or a 3- to 2-leafed plants, as well as other permutations) (Anderson et al. 2002; McGraw 2003 and unpublished data 2006; Van der Voort 2005; Farrington 2006).
Plants can also produce the same number of leaves for multiple years (Van der Voort 2005). Furthermore, the leaves of ginseng can senesce (a natural die-back of the plant) due to drought or other factors during the growing season (Carpenter and Cottam 1982). Although not as common, true dormancy has also been observed in wild ginseng populations (McGraw and Furedi 2005; Farrington 2006); dormancy in plants for more than one growing season has also been documented in the wild (Farrington 2006).
6. Although wild 2-leafed ginseng plants (approximately 4 years of age) have been observed to reproduce (Carpenter and Cottam 1982; Lewis and Zenger 1982 and 1983; Anderson et al. 1993; Charron and Gagnon 1991; Dunwiddie and Anderson 1999), plants usually have 3 leaves (approximately 5–9 years of age) before producing fruit in any quantity (Charron and Gagnon 1991; Lewis and Zenger 1982; Anderson et al. 1993; Persons and Davis 2005). Fruit production is positively correlated with age and size of plant (leaf number and leaf area) and increases as plants age (Carpenter and Cottam 1982; Lewis and Zenger 1982; Anderson et al. 1984 and 1993; Schlessman 1985; Schluter and Punja 2000; Lubbers 2006).
7. Ginseng produces flowers in late May to June. The species has a mixed mating system (both self- and cross-pollination) (Carpenter and Cottam 1982; Schlessman 1985). Plants have been observed to be cross-pollinated by bees and flies in the families Halictidae and Syrphidae, respectively (Carpenter and Cottam 1982; Lewis and Zenger 1983; Schlessman 1985). The male (anthers) and female (stigma) parts of flowers are reported to mature at different times to allow cross-pollination to occur (Small and Catling 1999). Several field studies have shown that, in the wild, more flowers are produced than actually develop fruit, and seed production is much lower than its potential.
8. Although fruit maturity is variable across and within geographical regions (McGraw et al. 2005), green fruits first appear in July and August and reach maturity in the autumn, when they turn red (Anderson et al. 2002; McGraw et al. 2005). The berry-like fruit is typically two-seeded (Carpenter and Cottam 1982; Lewis and Zenger 1983; Anderson et al. 1984 and 1993; Dunwiddie and Anderson 1999), although three-seeded fruit is not uncommon (Schlessman 1985; Anderson et al. 2002). Dispersal is usually passive, and typically fruit fall within 2 m (6.5 ft) of parent plants (Lewis and Zenger 1983; Anderson et al. 1993; Cruse-Sanders and Hamrick 2004a; Van der Voot 2005).
9. Germination of seeds usually occurs 18–20 months after dispersal (Lewis and Zenger 1982; Anderson et al. 1993; Hackney and McGraw 2001). Although it may not be significant in number of seeds (Anderson et al. 1984; Lewis 1988; Charron and Gagnon 1991), ginseng is reported to form a short-term seed bank of 5 years or less (Lewis 1988; Anderson et al. 2002; Van der Voot 2005).
Field studies show that seeds of ginseng fruits (regardless of color) planted at the recommended depth of 2 cm (ca. 1 in) in soil have a germination rate 8 times greater than seed scattered on the soil surface or naturally dispersed by plants (McGraw 2003a). Planting seeds from harvested plants significantly contributes to population growth and the long-term survival of ginseng (McGraw 2003b; Van der Voot 2005; Farrington 2006). Moreover, seeds from red fruit germinate at nearly 3 times the rate of seeds from green fruits (McGraw et al. 2005).
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