Gotu Kola and Goldenseal in Greenhouses

I have your 1994 catalogue, and have just requested your 98 catalogue via email from your website. I have a small mom and pop greenhouse business in San Marcos, Texas, and I am interested in growing an herb in the greenhouse that will boost our cash flow. (Currently we are mostly growing a variety of salad greens for a custom Mesclun or spring mix, and we also grow some basil). The greenhouse is fairly sophisticated in that it has 3 levels of cooling control with 5 computer controlled fans, vent, and a huge evaporative cooler. And, we use a 60% Aluminet shade cloth, which greatly aids in controlling heat.
Our system is an Aquaponics operation, which means our water and nutrients come from 6 large fish tanks inside the greenhouse itself. Unlike conventional hydroponics systems, that is, because we operate an aquaponics rather than a hydroponics system, we are now organically certified by the Texas Department of Agriculture. Due to the Aquaponics gravel beds and fish tank components, our inside temperatures are modified or moderated from that of a simple greenhouse with the same structural components, I believe. This was borne out and tested this summer, in the hottest weather we have seen here in Texas in my memory. During that period, we grew delicate salad greens that normally like 65 to 75 degrees for culture conditions. During the hottest part of the day, back in July, we were experiencing up to 108 (and beyond) degrees outside temperatures, and the greenhouse might get up to 90 or 91 degrees, but the "sensible" heat felt less than 90 degrees. I am giving you this background information to let you know that I think we can grow some kinds of plants which might otherwise not be grown in this area due to our harsh summers.
Anyway, we would like to investigate a couple of herbs, such as goldenseal and gotu kola, to sell to local health food stores, etc. I know that goldenseal is a woodland plant and likes shade and cool, but, given our experience with the salad greens, I just have to wonder if we shouldn't at least try to challenge conventional wisdom once again, just to see if it will work? And what about gotu kola?
Any advice you might give us about these two candidate herbs, or any other herbs you think might work for us- from the standpoints of feasibility of culture as well as market demand- would be greatly appreciated.

Your operation sounds very interesting.
We have grown goldenseal in our greenhouses and without fail by the time the hot weather arrives in June and July, our plants whither and die. We believe that it is not impossible to grow it in greenhouses, but temperature is going to be a key. We don't have particularly good cooling – just fans – but if you could keep the temperature down to below 80 degrees Fahrenheit then you *might* have a chance – but I rather think you will have many problems.
Gotu kola is completely different. You should have absolutely no difficulty at all growing it. It is very easy. The only challenges are that it has is not easy to establish from seeds (and seeds are not available in bulk quantities) and that it is not as marketable as better known herbs such as goldenseal. However, if you have buyers who have already expressed an interest, gotu kola is definitely worth trying.
Other herbs you might try? Growing medicinal herbs in greenhouses is a relatively new field. The biggest challenge is to figure out how to overcome the high capital cost of greenhouse growing, because your main competition is field produced herbs with far less capital cost.
Where you may be able to parlay the greenhouse into an advantage is in the fresh herbs market. This is better established in the culinary herbs market and salad greens, but we believe that there is a small but important niche market for fresh medicinal herbs. There are several growers trying that with fresh ginseng (though not greenhouse grown) and echinacea.
The case made for greenhouse-grown echinacea has been that it matures much faster, and the resultant product is cleaner and more consistent, than field produced material. However, the economics of greenhouse-grown echinacea has not been proved, and there are still many questions about the best procedures for growing and processing in a greenhouse environment.