It’s a common enough situation for those just learning herbal medicine. Look up a disease or a symptom in a book and there’s a laundry list of herbs. How do you know which herb is going to be best? It can be confusing for a beginner, but there are some basic guidelines that almost all herbalists use and are relatively easy to learn. In fact, you could think of it as an equation.
The beauty of plant medicine (and the challenge, I might add) is that herbs are complex, often with more than one use. And yet they are also subtle, meaning they are both gentler on the body than pharmaceuticals yet also deeper-acting. A good herbalist must know their herbs well, just as any craftsman must know their tools.
But it’s not about learning more and more herbs – it is much better to learn a few plants very well than have a large but shallow materia medica. Each plant can be used to treat many things, and the more we are able to match the complexity of the herb to the complexity of the person, the better chance it will actually work because it will be more specific for their imbalance. Don’t look for the “new best herb” – find the herb you already know that is best. The perfect herb for a person is often the herb that you have on-hand and best matches what you’re looking for.
However, no matter how complex a problem is, once you answer three basic questions, you can come up with a short list of useful herbs. This creates an easy equation to narrow down your choices and create better results. And although it works best when you know your herbs well, to use this equation all you really need is a good reference book.
The basic equation is simple:
Action + Body System + Strength = Herb Choice. 

Now you’re ready to think about herb choices.
The simplest approach is to figure out which action is needed and the location in the body you want to affect. Look up an herb in any quality herbal book and you will see a list of the aforementioned herbal action terms (e.g. diuretic, anti-inflammatory, astringent, etc.) Many books will also have a complete list of these actions and their definitions. Then you need to figure out where in the body the herb has its greatest affect, what is its “system affinity.” And finally, how strong an herb it is. You will generally need stronger herbs for problems that are short-term (acute) and gentler herbs for chronic issues.
This will get you a short list of very good herb choices, and it is fine to stop there. To get an even more accurate herb choice, you can fine-tune your choices with three more elements. Namely, thinking about the relative strength of the herb (tonic, acute, or low-dose), its energetics (hot or cold, building or clearing), and any specific indications of the plant (additional attributes not obvious from the previous qualities).
This is our basic equation. To illustrate its usefullness, let’s look at each of these steps and learn more about how to choose the most appropriate herb for a specific problem AND the unique person.
Most herb books will list the action of each herb and have a glossary to define these terms, so we won’t cover every possible term here. Some terms are most likely familiar (anti-inflammatory, diuretic, expectorant, analgesic), and some are unique to herbal therapy (alterative, adaptogen, nervine).
Think about these as a short hand version of what the herb can do, its “resume” so to speak. You won’t know everything about a plant by knowing its action terms, but it does give you a broad idea of the herbs actions, and these are the basic categories that most all herbalists use when beginning their herb choice.
So begin by thinking about what action is needed – do you need an anti-microbial herb or an anti-allergy herb? Someone with edema (water retention) might do well with a diuretic herb, someone with cramps could use an anti-spasmodic. We could go much deeper into treatment strategy and how that affects action choice, but that is beyond the scope of this introductory article.
Herbs tend to have an “affinity” for certain body systems (in old books this was called its “tropism”). So it’s not enough to choose an anti-spasmodic for cramping – Black Cohosh is excellent for menstrual cramps, but Ginger would be a far better choice for cramping in the digestive system. Even within an action like “nervine” (a tonic for the nervous system), you could use Skullcap to relax tension from over-thinking, while Pedicularis would be better for muscular tension and over-use of the body.

This information is not always included in an herb book directly, so sometimes you need to read into the text and see what diseases the herbs treat, then think about what system that affects.

When it comes to the strength of an herb, I like to think about there being three main categories: Tonics, Acute herbs, and Heroic herbs. Although not every herb fits neatly into one of these categories, understanding the strength will help you better match the herb to the severity of the imbalance.

Tonic herbs are the backbone of modern herbal medicine. These are herbs that can be taken for long periods of time and create balance in the body, or nourish and tone either the whole body or one particular organ system. These herbs really shine in both preventative medicine and also in long-term care and healing of chronic disease.

Acute herbs are used for situations that are going on right now. When someone has a cold or a headache, or is in acute pain, then we reach for one of these remedies. They are more about treating an illness or symptom than about creating balance in the body.

Heroic herbs are strong herbs that have a strong effect on the body. We try to avoid these in general, but there are times when a very strong remedy is called for. They have the possibility of throwing the body out of balance, but they can also save lives. This type of healing, by the way, is the focus of modern medicine; whereas herbal medicine prefers using building and balancing herbs.

Here’s an example. If it is flu season and your friends are getting sick and you feel like you’ve been working hard, you may want to take Astragalus because it is an immune “Tonic” that helps restore the strength of the immune system and build more white blood cells. But if you are already feeling sick, then it is too late to build. You need to fight the infection! So you could take Echinacea as an “Acute” herb to stimulate your immune system. Echinacea is better at getting the body going than at preventing disease.

If the infection got really bad, you could go for some of the heavy hitters, but don’t use “Heroic” herbs unless you really know what you’re doing. There are herbs like Poke root, Lomatium, and Coptis that could be used for bad infections, and antibiotics would also fall in the Heroic category as a substance that can kill infection but often has side effects.

If your herb book doesn’t mention the strength of the herb, look at the dosages to get a better idea of how strong it might be. Since different herbalists use different dosing strategies, the best bet is to compare dosages within the book.

These are the 3 basic characteristics to think about when choosing an herb to help someone. This article will be added to and edited again in the near future, so let me know your questions in the comments section below, and I will include my answers in the next version right here.