Stratification of North American Ginseng Seed

Freshly harvested, immature (green) seeds of north american ginseng (Panax quinquefolius L.) were stratified for 12 months either traditionally in buried wooden boxes outdoors, or in plastic pails in a controlled environment room [3 ± 0.2 °C (37.4 ± 0.11 °F)], 85% ± 5% relative humidity) for about 9 months followed by about 3 months at 20 ± 2 °C (69.8 ± 1.1 °F). Embryo growth in Stage II (mid-May to late August when direct seeded) was more rapid [0.016 versus 0.009 mm·d–1 (0.00062 versus 0.00035 inches/day)] under controlledtemperature conditions. Seedling emergence rate did not vary between treatments. Root dry weight (economic yield) was similar for seedling, 2, 3, and 4-year-old plants whether grown from traditionally or controlled-temperature stratified seed. Controlled-temperature stratification of north american ginseng seed is an acceptable alternative to traditional outdoor, in-ground stratification. North american ginseng, a perennial herbaceous plant grown for its fleshy root and seeds (Proctor, 1996; Proctor and Bailey, 1987), is propagated by seed (Proctor and Louttit, 1995). Traditionally, ginseng seed harvested in August or September, is placed in a wooden stratification box for about 12 months and then directseeded into raised beds. Seeds germinate the following spring, some 18 to 22 months after seed harvest. A number of problems in ginseng stand establishment have been linked to the seed stratification procedure. For instance, Proctor and Louttit (1995) reported premature seed germination (up to 10%) in the seed box after only 8 months of stratification, a condition likely due to fluctuating temperatures. These premature seedlings die and associated fungi may be potential pathogens that might colonize other seed in the box. Also, ginseng seed harbor pathogenic fungi and seed can be colonized during stratification despite fungicidal treatment of seed (Tianyi and Weiqun, 1992; Ziezold et al., 1998). Seepage of water from adjacent soil into stratification boxes may introduce unwanted fungi. Because of these problems stratification of ginseng under controlledtemperature conditions and aboveground has been suggested as a viable alternative. The objective of this study was to compare the traditional method of seed stratification with a controlledtemperature, above-ground method. Materials and methods Two experiments were carried out at a Winco Canadian Ginseng Ltd., farm at Vanessa, Ontario, from September 1992 to October 1997 (Expt. 1) and from September 1993 to September 1997 (Expt. 2). Since seed handling was similar in each experiment, the common procedure is described and related dates are given. The fruit (berries) were hand-harvested in late August/early September in 1992 for Expt. 1 and in 1993 for Expt. 2. The berries were mechanically depulped, surface sterilized with formaldehyde and mixed with sand following traditional practices (Oliver, 1998; Ontario Ministry of Agriculture, Food and Rural Affairs, 1999; Proctor and Louttit, 1995). Four stratification treatments were established. The seed-sand mixture was placed in the buried wooden stratification box on 10 Sept. 1992 (Expt. 1) and 21 Sept. 1993 (Expt. 2) where it remained until 23 Aug. 1993 and 23 Aug. 1994, respectively. This traditional in-ground stratification was considered the control. For aboveground indoor stratification (treatments 2, 3, and 4), nine samples, each of 10-L (0.35-ft3) plastic pails of seed-sand mixture, were taken randomly at the time of box filling and held at 3 ± 0.2 °C (37.4 ± 0.11 °F) for three different time periods: treatment 2 until 15 Apr., treatment 3 until 1 May, and treatment 4 until 15 May in each of the 2 years. There were three samples (pails) in each treatment. At the end of each