Wild ginseng grows best beneath a stand of mature hardwoods on a northeast-facing hillside that has thick, moist leaf litter and little undergrowth. Such a location also is ideal for cultivating ginseng, but a well tended garden can be made to succeed on most any modestly fertile site within ginseng's wild range, if it has both good shade and good drainage.
Outside the wild range, too much summer heat, too little rainfall (less than twenty inches annually), or lack of cold stimulation over the winter months may prevent success.
drainage is necessary, and it's extremely difficult to provide good drainage
unless your planting site has at least two degrees of slope - more than five degree is highly
desirable. Grades almost too steep to till are often used. North and east
facing slopes usually have more favorable temperature and soil moisture
conditions, while southern and western faces are warmer and drier. In the
cooler northern climate and at higher altitudes in the south, the direction of
exposure is less critical.
If all your land predominantly slopes toward the south or west, the best planting site will likely be where the snow stays longest on the ground. If you're so far south that snowfall is rare, then a north or east face is nearly essential for success.
Ginseng requires a minimum of sixty-five percent shade, and seventy eight percent is optimal over most soil types. Too much sun can burn the leaves and directly kill the plants, or the excessive heat may put the plants in stress and make them extremely vulnerable to disease. More than ninety percent shade will often produce spindly plants and extremely slow root growth.
Without technical equipment you can't walk out into your woodlot and measure the exact percentage of shade provided by your trees. Fortunately, natural growth succession usually spaces mature hardwood trees at distances which produce shade within the limits acceptable to ginseng. A dense understory of young trees or undergrowth that hinders walking indicates too little shade. The leaf canopy should produce a mottled pattern of light and shadow on the forest floor that continuously changes during the day so that no areas are in continuous light or shadow. There also should be a noticeable cooling sensation on a hot summer afternoon when you walk from the open into your woodlot. A maximum temperature of no more than eighty degree is desirable.
Some trees produce better shade than others. Bigger, taller examples of any species are preferable because they usually have a broader, higher canopy, allowing better air circulation over your beds. Trees with deep root systems also are more desirable, because they compete less for surface soil moisture. I like a forest site with a mixture of hardwoods, even including a few evergreens. In the south, the best trees are probably black walnut, hickory, poplar, and beach. The particular hardwood species, however, is not critical if other site characteristics are good.
In a survey done by Dr. C. R. Roberts, professor of horticulture at the University of Kentucky, wild ginseng was found most frequently under maple, beech, dogwood, poplar, oak, hickory, walnut, redbud, gum, birch, and elm, in that order. In other parts of the country, ginseng is found under species such as ash, basswood, buckeye, elder, locust, and sycamore. Maple and dogwood, two of the top three, are not the best for farming under, because their root systems are both shallow and dense. The ginseng will suffer less than the grower-who must cut through the abundance of tough tree roots to initially prepare his beds, then years later dig his ginseng that is now enmeshed in a thick, new growth of roots.
Soil and Drainage
Ginseng grows in a wide variety of soil types, from black sand through clay to heavy black loam-as long as they are well drained. Good results are obtained in heavier soils only when there is a decidedly sloping terrain or a porous, granular subsoil. Excess surface water must leave the root are immediately after heavy rains.
Ginseng hates wetness, yet loves moisture. On the one hand it does poorly in heavy, soggy soils-especially bottom lands. The roots will rot if planted in low-lying areas. On the other hand, ginseng requires at least twenty inches of annual rainfall. Lack of available soil moisture greatly reduces germination, root growth, and seed production. On naturally drier south and west facing slopes, look for some clay content in the soil. On other slopes, loamy soils usually retain sufficient moisture even during dry spells. Check your prospective site during a dry period to make sure the soil under the leaf litter retains some moisture.
Undoubtedly the best soils are humus-rich sandy loams located on north-or east-facing slopes. With proper treatment, however, almost any woods dirt can be conditioned for ginseng. If you have a dense soil on an otherwise promising planting site, consider tilling in a few inches of either pine-bark humus or well-rotted organic matter, such as compost, old leaf litter, or decomposed sawdust. This will loosen the soil, and provide better air and water movement as well as increased fertility.
Associated Plants to Look For
Occasionally I'm asked to look over a perspective planting site. In addition to checking shade, drainage, and soil type, I always observe the herbaceous undergrowth. I like to find a few plants similar to ginseng - trilliums, jack-in-the-pulpits, mayapples, rattlesnake ferns, or wild gingers. Of course, a little wild ginseng is most encouraging, but it's increasingly rare. Poison ivy and Virginia creeper are so common that they are not really indicator plants, but ginseng often grows in their midst. If the forest floor is completely bare, naturally that's a bad sign.
Dr. Roberts also surveyed the understory plants most frequently found near ginseng. Bloodroot, ginger, Solomon's seal, ferns, mayapple, golden seal, jack-in-the-pulpit, and Virginia creeper - in that order - were most commonly associated with wild ginseng in Kentucky. In the upper midwest and northeast, no doubt there are other perennials that commonly cohabit with ginseng.
Understand that the presence of one of these associated plants does not necessarily mean that the site is suitable for ginseng growing. Jack-in-the-pulpit, for instance, will tolerate more sun than wild ginseng. Similarly, mayapple will grow in areas too wet for ginseng.
There are several instances in the literature where the prospective grower is advised not to plant under oaks, and I've seen beautiful gardens in oak groves. However, oaks sometimes grow in poor clay soils that have only a thin layer of humus-rich topsoil, hold moisture poorly, and are very acidic. Naturally, ginseng won't thrive there.
If you're considering an oak-shaded hillside as a planting site, check it out carefully. You may need to work in decomposed organic matter to improve soil tilth and dolomitic lime to reduce acidity. Your county extension or soil conservation agent can help you measure acidity(or pH) and, if needed, recommend the appropriate amount of lime. Ginseng does best in soils with a pH of 5.5 or better, and the pH level in a ginseng garden normally falls over a five-year growing cycle. If your soil is more acid than, say, a pH below 5.0, then you should definitely raise it to between 5.0 and 6.0. You'll also need to check the pH level each year, because oak leaves-especially red oak, black oak, and water oak-add tannic acid to the soil as they decompose.