Growing of Roseroot (Rhodiola rosea)

Earlier this spring I purchased seed from Richters for growing of roseroot. It is growing extremely well here in Alberta and am now curious if we can start growing this herb on a much larger scale.
My questions are as follows:
What kind of fertilizer program does it like?

We have no information on the effects of, or requirements for, fertilizer on this crop. My guess is that the plant may respond favourably to very light applications of fertilizer but not much more.

Best type of soil and other conditions?

In its natural range, it is found in both moist and dry sites, but good drainage seems to be to be an essential requirement. We have noticed that it does not do very well in peaty or loamy soils. It does well outdoors in our sandy soil in Goodwood; but in pots in typical peat-based greenhouse soil media it does poorly.
It is native to Canada and is rated very hardy, surviving USDA zones 1-7. In Canada it is confined to coastal and alpine regions, and interestingly it is not found in similarly cool zones in Canada's interior. Despite what its natural range may suggest about the plant's needs we have found that the plant does just fine in non-coastal or non-alpine locations provided the drainage is excellent. Indeed this species and related species are grown as ornamentals in rock gardens where the drainage is typically excellent because of slope and the gravelly soil.
We know that the plant is cultivated commercially for the roots in Russia and Finland. There is a monograph on the herb in the book "Canadian Medicinal Crops" by Ernest Small and Paul Catling (available from Richters). The monograph does not have much on the cultivation of the plant, but it is well worth looking at if you are serious about growing this crop commercially. For example, it is useful to know that the plant is found on "moist cliffs, ledges, talus, ridges, and dry tundra. Northern plants of North America typically occur in crevices or among mats of moss and other vegetation, often near shores, and sometimes in rather rich substrates; southern plants tend to grow on north-exposed cliffs in alpine regions."

Is it just the root that would be harvested or can other parts of the plant be used as well?

The root is the part that is of interest commercially. The leaves are said to be useful for burns, bites and other skin irritations, much like Aloe vera; but this use is of no economic importance currently.

Are you aware of any companies that buy this product from other commercial growers?

So far commercial roseroot production is at a very early stage in North America. Growers are still experimenting with the crop and little or no commercial North American production is currently on the market. But we do feel that the potential for this crop is large. It is becoming better known every year and we are seeing increased attention from industry.

Harvesting of the root: what time of year, does it have to kept out of the sun, dried down to what dryness, can the root be harvested after 4 years?

The Small and Catling monograph says that Russian researchers have looked at optimal harvesting times with respect to rosavidine and salidroside, two of perhaps many compounds that are thought to be medicinally active. Other research has looked at postharvest handling of the roots. An extensive list of references to the Russian literature is provided, some of which is in English and the rest you will have to get the help of someone who can read Russian.

I am also looking for the same type of info on the plant called ashwagandha. Not able to find much info on this so if you have found a good site, please advise.

Ashwagandha is quite easy to grow. It germinates well from seeds, and grows well as a row crop in our sandy fields in Goodwood. It is not hardy in Canada so it has to be treated as an annual. The seeds need to be started in plugs indoors about two months before outdoor planting time in your area. It prefers dry, stony or sandy soils, but seems to do well enough in other soils also. It prefers full sun and tolerates partial shade (although we suspect that may be true of tropical zones only). It can reach up to 2 metres in height, but we have only seen it get up to 60 cm. Its spread is likewise known to reach one metre but we have only seen the spread reach 30-45 cm. The roots are harvested in fall after the first frost.