The two sources of supply of medicinal plants are collection from the wild and cultivated material. In many traditions of medicine, wild harvested material is considered to have higher therapeutic benefits, and therefore commands a higher price.

Plant material sourced from the wild such as bark, leaves, fruits, herbs, flowers, wood or roots are collected from many locations including open pasture, waste agricultural lands, gardens, roadside and forest land. Sometimes they may be ‘weeds’ found in agricultural or waste land, or plants or plant parts found in horticultural areas. The bulk of the material traded, both domestically and internationally, is still wild harvested and only a very small number of species are cultivated. Although the major part of the wild harvested material is sourced from developing countries, a surprisingly high amount is also gathered in developed countries. For example, in the United States, an estimated 200 tonnes of Echinacea angustifolia is wild harvested annually and 220,589 pounds of ginseng were wild harvested in 1992. In France, more than 500 species were wild harvested during 1988–1989, including those used homeopathically.

A significant part of wild-harvested material now traded commercially, with very low prices being paid to gatherers, commercial plant gatherers often ‘mine’ the natural resource with no concern about its sustainability. Prices of medicinal plants collected from the wild tend to vary in a cyclic manner. Price cycles of 6 to 7 years are common as the availability of many plants goes from over supply to scarcity very quickly and then takes several years to return to normal. Of particular concern for the sustainability of the wild resource is the fact that many of the materials are roots of plants, which are the most difficult plant parts to harvest sustainably. Many countries do not have regulations controlling the collection of material from the wild. India has banned the export of several endangered wild species in the form of raw material, with no such restrictions however on the export of finished herbal products containing such species. Despite this, an estimated 95% of medicinal plants collected in India are gathered from the wild and the process of collection is said to be destructive. Equally a major part of the high-range Himalayan plants are wild harvested and many of these are close to extinction from over-harvesting or unskillful harvesting, e.g., Nardostachys jatamansi, Aconitum spp. An estimated 70–90% of medicinal plant material imported into Germany is wild harvested and only 50–100 species among these are currently propagated on a large scale.

In China the output of the area cultivated is estimated to be between 300,000 and 400,000 tonnes whilst in 1994 the total demand for medicinal plant material was 1,600,000 tonnes. This huge gap must be made up by wild harvested material. TCM tends to use the roots of plants, which are the most difficult plant parts to harvest sustainably.

According to Lewington (1993) it is difficult to ascertain the precise origin of medicinal plants entering world trade as traders are reluctant to reveal their sources. It is however certain that the vast majority of the medicinal plants come from wild sources. There are very few plants that are only collected from cultivated material such as Catharanthus roseus, Chamomilla recutita, Cinchona sps, Digitalis lanata and D. purpurea, Duboisia spp, Mentha piperita, Papaverum somniferum and Plantago ovata.

Quality control requirements for cultivated material are becoming increasingly important due to stringent drug regulations in many countries. With cultivated material being more suitable for large-scale use, countries such as Argentina, China, Hungary, India, Poland and Spain cultivating plant material on a large scale are now looking at more successful commercial cultivation to produce high-quality plant material to compete in a highly competitive international market.

Due to the high cost of cultivation, it is often done under contract and only those plant species used in large quantities or in the production of derivatives and isolates that require to pass critical standardization parameters are cultivated.

Globally the areas cultivated are limited because cultivated material bears higher production costs, must have secured land ownership or access and requires more expensive and sophisticated management expertise. Costs may be carried for long periods and the low prices of wild-harvested material make the returns for cultivation low in many cases. The very long supply chain between the farmers and primary collectors and specialized wholesale suppliers is the reason for the former receiving low prices for their products.

As collection from wild is still more common than cultivation, huge differences in the quality of materials occur. Amount of active ingredients vary depending on the region the plants are grown, plant parts collected, method of harvesting and their storage conditions. Adulteration of wild drugs is a common problem as there can be no guarantee over the uniformity of the raw material. According to Cunningham (1996) medicinal plant trade passes through the following main channels:

1. Trade at the national level is the first involving hundreds of species through regional medicinal plant markets.
2. Trade across national borders, however within continents, is the second. This informal trade channel consists of fewer numbers of species with many unfortunately being threatened. E.g. Nardostachys and Valerian being traded from Nepal to India.
3. More formal international export trade is level three in which several hundred species are traded in significant volumes.

Major part of the plant material is sold by trading companies who hold enormous stocks and also have facilities to undertake the quality controls required or raw material used in the production of drugs. They play an important role in the medicinal plant trade, partly because of the large quantities they purchase which enables them to more or less dictate the price. Such traders are also able to guarantee the supply of material of specified standard of quality at a fixed price. This price and quality guarantee is a major incentive to the end user, for whom cost, quality, reliability and flexibility are said to be the key requirements for purchasing pharmaceutical raw material. In addition there are brokers who engage in purchase and sale of plant material adding their commission. Having contacts at the purchasing level they do not stock material and have no warehousing facilities. Recently emerging are the ecological traders. According to Lange (1996), they source botanical material for use generally by the smaller herbal medicine/health product companies and alternate practitioners. Such traders generally deal with organically cultivated products and are more discerning/ethical in their purchasing approach. Having shorter sales routes involving fewer parties, they establish their own contacts in the source countries and purchase only raw material and not extracts.