Ginseng production in Ontario

Introduction

Ginseng is a slow-growing herbaceous perennial cultivated for its highly valued root as a medicinal herb in various temperate climate zones, particularly North America and Asia. Botanically, Panax quinquefolius, the species cultivated in North America, differs slightly from the principle species native to Asia, Panax ginseng. Other species of ginseng are cultivated to a lesser extent.

Ginseng is a member of the Araliaceae family of plants, which includes wild sarsaparilla, dwarf ginseng and spikenard. All of these plants can be found in the forests of Ontario; the climate and soils of South Central Ontario are ideally suited to the production of ginseng.

About 85% of the ginseng root grown in North America is sold to the Asian market, where there is a considerable distinction between North American and Chinese ginseng based on their medicinal uses.

History

Ginseng has a special place in the history of Ontario and Quebec. Roots were used in traditional Native medicines. In 1715, a Jesuit priest recognized the plant from descriptions out of China and initiated export to Hong Kong. At one time, ginseng trade rivalled the fur trade. All the roots were harvested from the forests, and now truly wild ginseng is rare in Ontario and Quebec. In June 2008, the Endangered Species Act, 2007, came into effect in Ontario, making it illegal to plant, harvest, possess, buy, sell, lease or trade ginseng collected from the wild in Ontario without authorization through a permit or agreement under the Act.

Under the Convention on International Trade in Endangered Species (CITES), a permit is required for export of ginseng. This permit is necessary for field-cultivated roots but not for live plants, seeds or processed root. The exportation of wild ginseng root from Canada is prohibited. Ginseng was first cultivated in Ontario in the field under artificial shade in the late 1800s, near Waterford, Ontario. It wasn't until after the Second World War that the ginseng industry began to expand, and until the 1980s, there was a limited number of growers in Ontario. Since then, acreage has increased, and in 2010, there were more than 140 producers of this root and over 2,200 ha (5,300 acres) under cultivation.

The plant

Ginseng is a herbaceous perennial that develops from seed planted in the fall. Each autumn, the stem and leaves fall off the plant. In the spring, around mid-May, a single shoot emerges. This cycle continues until the root is harvested. Under field cultivation, the root is harvested 3-5 years after seeding.

In its first year, the ginseng plant is small, resembling young poison ivy. It has a single leaf with three leaflets at the top of the stem and is 15-25 cm tall. In the second year, a single shoot bears two leaves, each with five leaflets arranged in the shape of an open hand. In succeeding years, there are three to four leaves on the plant and occasionally five (Figure 1). The number of leaves increases each year, up to the fourth year. After that, stems may become thicker but the actual leaf number seldom exceeds four. Plant height is related to age for the first 3-4 years, and ginseng over 3-years-old can reach a height of 45-60 cm. Under cultivation, ginseng may be taller.

Flower heads develop on a single stalk that arises where the leaves are attached to the stem. The flower head is present at the time of emergence in the spring. Flowering occurs over a period of 3-4 weeks in mid-summer on plants 3 years and older, and occasionally on 2-year-old plants. The flower is an umbel with 30-40 blossoms. Flowers open sequentially from the outer edge inward and are self fertile. Pollination can occur between flowers on a single flower head or between flower heads. Pollination is assisted by bees and insects.

Figure 1. Diagram of a typical 4-year-old plant. (Courtesy of Tiffany Wybouw)

After fertilization, berries form and turn from green to a bright red when ripe. Each berry contains two irregularly shaped seeds, each being approximately 0.5 cm in diameter and slightly longer than it is wide. At this time, the embryo is immature and very small.

Ginseng has a fleshy branching tap root with a rhizome at the crown. It is on this rhizome that the bud that will be next year's shoot develops during the summer. This bud remains dormant during the winter months.

Most root growth occurs late in the season. The root of ginseng is also contractile, that is, it shrinks vertically each season. This allows the rhizome, which lengthens every year, to remain under the ground. It also provides the root with concentric "wrinkles" that are desirable in the marketplace.

There are no cultivars of ginseng. Field cultivation began by moving wild roots into protected gardens. Further expansion of acreage used seeds from domesticated wild roots. Selection of superior strains has not been achieved with this process.

Site selection

Choosing a good site for the production of ginseng is the most important thing a grower can do to ensure a healthy, high-yielding crop. In the wild, ginseng prefers a moist but well-drained site with high organic matter content and a pH between 5.5 and 6.5. To successfully cultivate ginseng in the field, duplicate these conditions.

Before seeding ginseng, correct the soil acidity, or pH. Apply lime to soil that is too acid to raise the pH. Private consultants and farm supply outlets can provide prospective growers with soil analysis interpretation and advice on corrective measures. Under acid conditions, below pH 5.5, ginseng appears to be more susceptible to disease and plants are generally unthrifty.

Drainage is also critical to the health of a ginseng garden. Under wet conditions, ginseng will become diseased, and the roots may rot. Maintaining moist yet well-drained soil can be challenging. While placing straw mulch on gardens can modify soil moisture, it is harder to change the natural capacity of the soil so it holds the right amount of moisture while excess water drains away. Drainage is also affected by the subsoil structure and by compaction.

Many growers allow 2-3 years to "build up" the soil before seeding a ginseng garden. This can be done with the incorporation of organic matter such as plow-down crops or the addition of composted animal manures. All of these activities affect the availability of nitrogen. Private consultants and agribusiness professionals serving the ginseng industry can provide advice on nutrient management

Garden preparation

Once a site is selected and pH, nutrition and drainage have been addressed, begin garden preparation. Before seeding, fumigate soil to reduce the population of nematodes, weeds and disease organisms. Fumigation is best done 4-6 weeks before seeding. Effective fumigation requires that soil be worked to "seedbed readiness" with a moisture level of approximately 60% field capacity. Seed ginseng 4-6 weeks after fumigation, when all of the fumigant has dissipated.

Climate modification

Ginseng is native to the floor of the mixed hardwood forests of Eastern North America. It requires only 20% sunlight, and in fact will senesce (age) and die if light intensity exceeds this level for any length of time. The high organic matter content of the forest floor provides a moist, well-drained environment. In the wild, ginseng usually grows higher on a slope where good drainage is ensured. To cultivate ginseng in the field, modify the field environment to resemble its natural preferences, by forming raised beds, applying straw mulch or other suitable material and erecting shade sufficient to filter 70%-80% of the sunlight.

Raised beds

Before seeding, form and groom raised beds for improved drainage :

• 22-35 cm high
• 1.5-m wide
• a 30-cm gutter on each side
• approximately 1.8 m between centres of the beds

To keep disease at manageable levels, design a garden with both good air circulation and surface water drainage. Orient beds so that surface water can drain out of the garden, if possible, in the same direction as the prevailing wind.

Mulching

After seeding, cover beds with 5-10 cm of straw mulch - about 28 large round bales (150 cm diameter) to the acre. After the second year, add half again as much straw. The mulch modifies both soil moisture and soil temperature. In winter, it prevents temperatures from dropping below the freezing point of the roots (around -10°C) and in summer keeps soil temperatures 5°C-10°C below that of an open grassed area. Mulch also prevents excessive moisture loss from the soil. Soil moisture under mulch can remain near 60% field capacity throughout the season. In very sandy soil, irrigation may be necessary but it is not generally routine.

Shade

Ginseng must be grown in 70%-80% shade. In the spring of the first year before the ginseng has emerged, erect shade structures of either wooden lath shade or polypropylene cloth shade on wooden or metal posts, 2.4-3.6 m high. The costs of erecting a shade structure vary depending on the type of material chosen. Most shade structures cost around $16,000 per acre in 2010. Remove shade wholly or partially each autumn after the plants have senesced and the leaves turn colour and fall, and replace it in the spring as plants emerge. Both the wooden lath and cloth shades are re-usable.

Seed handling

Berries containing the seeds emerge primarily in gardens 3 years and older (Figure 2). Pick the berries when they are ripe. At this point, the ginseng embryo in the seed is immature and very small, and before it can germinate, the seed must undergo stratification, a maturation process that lasts from 16-22 months. Harvest berries by hand; because the berries ripen sequentially, it may be necessary to harvest several times.

Figure 2. Seed emerges in red berry clusters on plants 3 years and older.

After picking the berry, remove the pulp, either by a natural fermentation process or by mechanical depulpers. Wash and surface-sterilize the depulped "green" seed and mix it with an equal portion of clean, coarse sand. Keep the seed moist at all times after depulping. In as little as 20 minutes of drying, the embryo will begin to deteriorate and will soon lose the ability to germinate.

To stratify the seeds, place the seed/sand mixture in seed boxes and bury it in the soil until late the following summer. When digging out the seedboxes, separate the seed from the sand, wash it, surface-sterilize it and keep it moist until planting.

Another method, more common in recent years, is to stratify seeds above ground in temperature-controlled chambers. This has the advantage of reducing the chances of contaminating the seeds with soil-borne, disease-causing fungi.

It is important to store stratified seed at acceptable temperatures - between 15?C and 20?C - before planting. If seed is held at temperatures that are too cool, it becomes dormant, and emergence may be reduced. When this happens, seedlings can emerge in the garden's second year, which results in considerable variation in root size, once the garden is ready to dig.

If seed is stored at temperatures that are too high, the seed will decay.

Seeding

Spread seed on prepared beds. Seeding equipment ranges from simple seed boxes to sophisticated air seeders. Some ginseng growers offer a custom seeding service to growers who choose not to own and operate their own seeding equipment.

Seeding Rates

Seeding rates vary from 90 to 145 kg/ha. There are approximately 17,600 ginseng seeds per kilogram.

Some growers seed at higher rates as a means of overcoming the poor germination of ginseng - 60%-70% germination is not uncommon. However, seeding at higher rates does not necessarily result in better roots and higher returns.

The value of ginseng roots is affected by their shape, and root shape is determined in the first 2 years of plant life. Research in North Carolina has shown that seeding at low rates of 45 kg/ha can produce roots more than twice as heavy as seeding at high rates of 140 kg/ha. In the same study, the difference in total yield was only 28% more for the denser planting. If long, narrow roots are more than 28% lower in value than chunky root, the increase in total yield will not offset the lower price of the small roots.

It has become obvious that ginseng cannot be produced organically at any of the common commercial seeding rates. To grow ginseng without the input of disease control chemicals, do not exceed a seeding rate of 45 kg/ha; 22 kg/ha is preferable. Root disease can still occur at these rates but cultural practices can control its spread better.

Production challenges

Environment

Ginseng is highly sensitive to the environmental conditions in which it grows. Both heat and drought adversely affect ginseng. Sites that are too wet invariably suffer from root disease, which can drastically reduce yields. Drought and heat will lead to flower abortion and consequent reduction in seed set. Heat can bring about stress-related leaf responses such as papery leaf spot. Lack of soil moisture will lead to reduced root weight. Exposure to direct sunlight will lead to the death of the above-ground portions of the plant. Gardens with poor air flow will experience leaf and head blight diseases.

Outside the forest, climate modification is the only means of addressing soil moisture and both soil and air temperature.

Diseases

Root diseases limit the yield of ginseng worldwide. Losses in yield from 30%-60% are not uncommon. Some root diseases affect root shape and quality. The serious diseases rot the root and completely destroy it (Figure 3). These diseases are caused by fungi found in soils throughout the ginseng-producing areas of the world.

Several foliar blights and seed-blasting diseases exert continual pressure on ginseng gardens throughout the season (Figure 4). These diseases may limit seed production and root weight but seldom account for actual root loss, as do the root rot diseases. The fungi that cause these diseases are constantly present in air currents. Gardens need protection from the time they emerge until they begin to senesce.

Figure 3. Some root diseases, such as cylindrocarpon disappearing root rot, can rapidly rot the entire root.

Figure 4. Foliar diseases, such as alternaria leaf blight, can cause considerable damage to the plant canopy and limit root growth, but do not destroy the root directly.

Insects

Insects in ginseng do not, as a rule, limit yield or affect root quality. In certain sites, cutworms may be a problem, but those sites usually have a high number of grassy weeds. European chafer grubs can also live on the grain crops used to hold down the straw in the first winter after planting and can cause damage to ginseng roots when the grains are killed off the following spring.

Leaf rollers, usually general forest-feeding species, may invade ginseng gardens, but little is know of the effect of these insects on ginseng yield. They forage from rolled leaf "nests" throughout the day and are usually attracted to older gardens and those near forested areas.

Another invader from the woods is the pit scale. The pit scale has a wide host range, and the ginseng family is among its preferred hosts. The scale attaches to the stem and petioles, causing them to become distorted and twisted. A plant normally 60 cm tall will twist down to 15-20 cm in height. This insect is found infrequently and its effect on the crop is unknown.

Other Pests and Disorders

Slugs can be a problem in the spring. The straw mulch creates an environment favoured by slugs, and they will feed on both shoots and any roots that are close to the soil surface, sometimes causing significant losses. Slug damage occurs most frequently near garden borders.

Ginseng is affected by air pollution. It is moderately sensitive to ozone and sensitive to sulphur dioxide. Sulphur dioxide damage, which occurs most frequently in the spring, appears as bleached areas on the leaf tips or bases.

Drought and heat will stress ginseng. The tips of leaves and sometimes the interveinal areas will turn papery white or tan. This is referred to as papery leaf spot.

Mice will occasionally invade a garden. The straw mulch provides protection from natural predators and mice will tunnel along the garden surface under the straw. These rodents will chew off stems and occasionally eat roots at the soil surface. Mice tend to seek shelter in ginseng gardens when the surrounding field crops are harvested in the late summer or fall.

Root and harvest handling

Harvest ginseng using modified potato diggers. Before roots are dug, remove the shade structure and scrape the bed surface clean of straw and plant debris.

After the digger has passed over the garden, remove roots on the soil surface by hand and place them in baskets. Take care not to bruise or break the root. Several passes over the garden may be necessary to remove all of the roots.

Completely automated digging equipment is available for purchase, lease or contract digging.

Refrigeration

Store the washed root under refrigeration for 4-6 weeks to improve the aesthetic quality of the root and make it less susceptible to heat damage during the drying process. Before curing, wash the root in a tumble washer drum to remove excess soil particles.

Drying

Ginseng root is usually sold as dried root (Figure 5). Dry roots in kilns modified to provide appropriate air flow and temperature. Place roots in shallow trays; rotate the trays several times during the drying process to ensure even drying of a mixture of sizes and shapes. With experience, growers learn to tell if a root is properly dried, based on how quickly and easily it breaks and on its surface texture and resilience.

Figure 5. Ginseng roots are sold dried with minimal grading before shipping.

Packing

Pack dried root in cardboard barrels lined with plastic bags in 45-kg lots. Buyers prefer a consistent mixture of "pencil root" and "chunky root" in each barrel, but no grading is done beyond that. Further grading of the root takes place in warehouses at the shipping destinations.

Many experienced growers with large facilities offer custom refrigeration and drying.

This Factsheet was authored by Sean Westerveld, Ginseng and Medicinal Herbs Specialist, OMAFRA, Simcoe. It is an update of an Infosheet originally written by Jan Schooley, former Ginseng and Medicinal Herbs Specialist, OMAFRA.