Hello,
I am not sure if this is Steve or Rich? I have spent 40 years growing in zone 8b, but grew up in a 7a area in E. Oregon. I have not gardened or farmed in it though. I have seen which plants do worse in the cold and so I won't suggest them. I am use to clay and just moved into an area with terrible clay and rock. As you mentioned the biggest thing is to improve the soil. The more
compost the better. I usually test new soil if I plan to be there a while as I want to know if it is missing any key minerals. For instance I had a farm that had no boron. If I would have tested immediately, rather than waiting, I would have known to add it and would not have had a lot of hazlenuts with empty shells.
Not having grown in your area and only having grown in a fairly temperate area, I am not an expert, but I have grown abou 200 different herbs for myself or to
sell and have an idea of what might grow where you are. So, rather than my top ten, I am going to give you the ones I think will do okay in a colder winter and clay/rock soil.
Many
medicinal herbs are fairly hardy. I am going to think of herbs that are either annuals and can grow in clay and rocks to some degree or perennials that can make it through the winter and can grow in clay and rocks. I would think about herbs that do not have tap
roots. For instance burdock, Elecampane, Marshmallow and Echinacaea angustifolia all have tap roots and won't do great in clay and rock. However Yarrow will be okay. In fact I usually get better Yarrow when it has to struggle a bit. If you really wanted Echinacea, I would suggest growing one such as Echinacea purpurea that will do a bit better in clay. Saint John's wort will grow okay there. I would look at the types of Mahonia or Berberis in your area. The species we have here go by the common name Oregon grape and they are all used. Species around the world are used similarly usually and I bet you have one there you could grow. Calendula can grow in most areas, although they would like garden soil. It is an annual. Opium poppy is also an annual, and so pretty to look at. Legal to grow in the states but not legal to extract latex. What will happen with the annual herbs like Calendula and Opioum poppy who really do better in richer soil is that they will not grow as big and will look slightly different than when given a more optimum environment. Gum weed grows well in E. Oregon and would probably grow fine there. Lobelia will probably make it there, as well as khella, Mullein,
nettle (it will grow, but really likes lots of nitrogen in soil and a lot of moisture). Ceanothus might do okay there, skullcap, thyme as an annual (it is
perennial but probably will get killed in the winter). Valerian might grow there. I have had it grow in a variety of env. and do okay although it prefers rich soil.
Once you enrich your soil, you
should be able to grow many medicinal herbs there easily except for those that will die in the cold of winter.
You might want to get a catalog from Strictly Medicinal Seeds -
https://strictlymedicinalseeds.com/ Richo has data in the catalog on growing the herbs that is helpful besides being a source for seed. I don't think he has much data
online, but Crimson Sage does at
https://www.crimson-sage.com/ and might be more useful.
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