There are a couple of easy to grow plants that are reputed to relieve arthritis pain. I'm up for that! The first, rose hips, can be found in most people's yards. Hips are the fruits that follow the rose flower and contain seeds for future bushes. If you didn't go crazy with the pruning shears, you should have some about ready to harvest. Heirloom roses are the best if growing rose hips is the goal. The studies I've seen on line used powdered rose hips to treat arthritis. I don't know if I'll break out the dehydrator or just enjoy a cup of rose hip tea each day. The tea sounds nicer.
The second plant can be made into an oil to rub on aching joints. Comfrey can be grown just about anywhere, I think. I had the same success with it in north Florida that I have in northern Michigan. It grows rampantly. Take a quart jar out and fill it up with leaves. Dig up some of the root, too. Chop the leaves and the root (after washing, of course) and return it to the jar. Fill the jar with cold pressed, extra virgin olive oil. Set in a dark place, like a cupboard, for one to three months. Strain and rebottle in some nice or official-looking dark glass bottle. Sunlight degrades the potency. If you discover that you have more than enough for your own use, bottle the excess to give as gifts to friends with aching joints.