Turmeric is another plant which I have in my garden but I'll need to move it into my greenhouse any day now. Ginger, and cinnamon (which is a shrub), I'll move them into the greenhouse, too. Those are good medicines. I have a database of 2500 plants, of which I would call 200 of them spices. I understand that my database is one of the most frequently visited at the USDA.

Considering the amount of data on handled by the USDA, that's quite impressive. Prior to your developing these databases that the USDA now keeps, did such databases exist? Did they have other herb or spice databases that you built on? Or are you the one who started this project?

They had none at the USDA. This started in 1977 or 1978, when the USDA accepted my assignment to a major anticancer program of the National Cancer Institute. At that time, I was sent to lead a small group to look for plants that might have anticancer activity, funded by the National Cancer Institute. So that means that way back in 1978, I started this database. It was primitive but we've improved it.

When I'm long gone, that will still be there. [In my own personal database] I've got almost three times as much data on some of these same questions as you could ask the USDA database tonight. I can take it proprietary, but if I can't find a buyer for it, I will dump it all into the USDA database and improve it probably five- or six-fold.

Either way, that's a wonderful legacy to have created and to pass on to others. You mentioned that, starting in the late 1970s, you were part of a project looking for potentially anticancer herbs. Where did that take you in your travels?

My whole lab traveled a lot. I had at least three trips to China, one trip to Panama (my old stomping grounds), one to Ecuador and one to Syria. And though not all of these were necessarily due to the anticancer program, in my USDA career I've been to over 50 countries.

I've had a charmed career! My God, I feel sorry for those people who spend their 30 years studying wheat or corn. I've landed from helicopters in ganja fields in Jamaica, in opium fields in Laos, and driven into coca fields back in the 1970s, when it wasn't dangerous. I was involved with the USDA alternative crops program where we would try to convince farmers that if they would phase out the narcotics, they would give them some interesting alternatives that might be remuneratively competitive.

How did that work out?

You may have noticed I used the words, "might be" … Because if we came up with a product that was more competitive, the narcs would just pay more. It was a non-winnable situation. I don't think the USDA would say that, though. Frankly, I think ganja is a great medicinal plant, much better than the synthetic copycats, which cost much more.

You've authored or co-authored many books on herbs, spices and foods. Some are academic treatises and others, like the classic bestseller, The Green Pharmacy, are for general audiences. Looking back on your publishing life, what work or works do you recall as the most satisfying, either because you loved writing them or because of the influence they had on readers?

Every time someone comes to a tour of the garden here, we show them a few of the books that I have on hand. And when they ask, "Which one would you buy if you were only going to buy one?" I always say The Green Pharmacy. It sold over a million copies in English and is now translated into eight languages. It was a turning point for me and I actually retired from the USDA a year early so I could work on that. I think it was one of the best decisions I ever made. That's why I have the Green Pharmacy Garden, with 300 species of plants, mostly built like the chapters of that book. We have a stone in the middle of a plot, say the Alzheimer's Plot. There, we'll see rosemary, sage, periwinkle and some of the plants that are still arguably better than the pharmaceuticals like Aricept.