So, for making ingredients and stuff like that, you can actually reference traditional medicine, Native American medicine, and just herbs in general. Also, for a more modern approach, pharmaceuticals. And, for the magic side to it, real life witchcraft and wiccan herbs can be a good reference.
Many times, it is only a particular part of the plant that is medicinal, with the rest either having no effect, or even being toxic. Dosage also plays a big part, especially with poisonous plants, because sometimes too little or too much of the herb could drastically change the effects of the medicine. Though, other times, the dosage has little effect on the medicine, or it takes chronic use to actually show any adverse effects.
For the magical side, sometimes the ‘magic’ is nothing more than traditional medicine and superstition. But, to make it actually magical, you could actually exaggerate the medicinal properties to a ‘magical degree’, lol. So, for a typical herb that helps with, say, a cold, it could instead cure diseases (whether this is straight from the plant or used as a potion, is up to you). For a herb that eases pain, it could instead remove every pain in the person’s body until the herb wears off (and you could easily add adverse effects to this one, like overdosing causes numbness and paralysis, etc). A good thought to keep in mind with magic, that can help keep it from getting so overwhelming, is that most magic is based on something real, like herbs that cure disease being based on a herb that just soothes a cold.
For symbolism, location and culture plays a big part. The size/shape and any medicinal/recreational properties of the plant can contribute as well.
So, for a very simple example, lol, say there’s a herbal plant with a heart-shaped flower. Eating the petals of the flower could be an aphrodisiac, or, for a younger audience, could be like an anti-anxiety or anti-depressant (or otherwise something that just increases happiness). And, say there’s a kingdom on the verge of war near where these plants grow. This plant will probably become a way to de-stress, and could even serve in love potions, happiness potions, etc. As a result, it might accumulate symbolic meanings of love and happiness, and maybe even good luck/fortune or similar meanings.
In short, the symbolism of the plants is likely going to be the most tedious part. Symbolic meanings can change drastically over time, as do the cultures that make them, and even the plants themselves (especially if they’re cultivated/farmed). But, overall, usually the meanings will reference something the plant can do, its appearance, its location and its ability to survive there (for more rare or hardy plants), or even just meaningful events/people/cultures that otherwise having nothing to do with the plant (like a famous individual collecting pretty flowers on their journey somewhere, and that plant is later associated with that person and their deeds, and possibly even considered to be one of the reasons that person succeeded).
I hope this helps, grin.
