This post was inspired by a comment in another thread, and was adapted from a post to c/gardening.
When people think of "medicinal gardens," likely what comes to mind are plants grown specifically for their medicinal properties, such as arnica, feverfew, mugwort, and tulsi: plants that have to be sourced from special seed catalogues and not something you can just pick up at your local nursery. In actuality, tons of vegetable garden staples have medicinal properties, including quite a number that are container-friendly!
For example, basically all culinary herbs have some kind of medicinal use. Probably the best known is sage (its witchy reputation isn't arbitrary!), however many other culinary staples such as mint, oregano, thyme, rosemary, cilantro, and parsley all have their own medical benefits too. Unlike more specialized medicinal plants that can require special processing (e.g. drying the root or creating a tincture), culinary herbs are also super easy to take, either by mixing them into food or brewing a tea (turns out you can just make tea from basically any sturdy edible plant part, including flowers, leaves, stems, roots, and seeds). Probably the best part about using culinary herbs medicinally is that while their medicinal effects may be on the milder side, you're unlikely to over-consume them or experience an interaction or side-effect, unlike other more pharmaceutical-grade plants like licorice root and ashwagandha that require care with use. This general safety, as well as their prevalence, ease of use, and multi-purpose nature, make culinary herbs fantastic entry-level additions to any medicinal garden.
Many popular garden flowers also have medicinal properties, such as jasmine, echinacea, calendula, lavender, and yarrow. It's important to note, however, that many medicinal flowering plants have also been bred for ornamental purposes, and while ornamental varieties probably still retain some medicinal properties, it's best to stick with varieties specifically bred for use as medicine as they tend to be the most potent (and maybe safer? I haven't heard that you shouldn't consume the ornamental varieties, so much as that they're not as effective).
Also worth noting is that for many medicinal plants, the medicinal part isn't necessarily that part that's most commonly consumed. Raspberry (and to a lesser degree strawberry) leaves, for example, are a common treatment for menstrual discomfort, even though the part we usually eat (the fruit) does not share the same medicinal qualities. Flowers, seeds, and roots can also be surprise sources of pharmaceutical effect in plants usually consumed for their other parts.
While there are lots of online resources for learning more about medicinal plants and pharmaceutical gardening, I'd also recommend seeing what print resources are in your local library. Growing and foraging plants with medicinal properties is an ancient human tradition... even non-human animals have been observed seeking out specific plants to alleviate various ailments!
My favorite edible container plants are perennials (as dealing with spent soil from annual plants every season is such a pain), and quite a number of those have medicinal properties. I've had tremendous success growing sage, thyme, oregano, mint/catnip, and calendula in smaller containers, and stinging nettle, mugwort, lavender, and echinacea in larger containers... all of which have medicinal properties of one kind or another. Quite a number of medicinal annuals are container-friendly too, such as tulsi. Some medicinal plants can even thrive indoors, such as aloe vera. Considering that many of these plants do double-duty (e.g. for culinary/pollinator-support/ornamental purposes), there's no reason why even the tiniest of gardens can't have some medicinal plants mixed in!
An obligatory disclaimer: before consuming a plant for medicinal use, you should of course always research the plant for potential interactions or side-effects (many herbs should not be consumed during pregnancy, for example, and some can interact with pharmaceutical drugs, which seems obvious if you think about it). You should also be careful which part of the plant you're consuming: many perfectly edible plants have toxic parts (nightshades like tomatoes and eggplants being a great example).
Okay but like, this actually does point at a potential cause (as in, why it persists/is so common in the population) of the condition, which is sexual selection.