Maybe
@P.P.Piggies is referring to a seed mix she's planning on planting, so the pigs can eat the plants later on? That's something I do.
In my experience, I think people in English-language forums rarely use herbs as an adjuvant therapy for some conditions, or as a prophylactic. In contrast, the two Russian forums I'm subscribed for have a host of lists with safe herbs, and how they can be used / for what conditions. I find it very useful, especially considering that wild guinea pigs frequently self-medicate by eating the right herbs for any conditions they may have.
What I'm using at home currently is dried nettle (not completely dry, just to the extent that it doesn't sting) for its anti-inflammatory properties to help an arthritic piggy. My two other pigs get a little bit of it, too, though only as a treat. As a result, my long-haired piggy's hair has become baby-soft and so shiny.
What I also use is chamomile, again as an anti-inflammatory and for upset stomach, and plantains for upset stomach/soft poops. The plantains grow very well in pots indoors too. Fennel, mint and dill are useful for upset stomach, and so is a fresh herbal infusion from these herbs, which is something most Russian owners offer pigs very frequently.
If you're interested in detailed lists of piggy-safe herbs and their application, I'd be happy to translate.
Just a note though - a lot of herbs can be rich in essential oils, calcium, phosphorus and oxalic acid. The vast majority of them really shouldn't be treated as food, but as a "supplement", provided only in moderation, when there's an actual medical need and after discussing it with your vet. They also shouldn't replace any vet-prescribed medication, but are just an adjuvant treatment, aimed to speed up recovery and provide a more natural approach to managing chronic piggy conditions. A lot of herbs can interfere with medications, e.g. slow down their absorption or potentiate their effectiveness. Most vets are trained in pharmacology and pharmaceutics, so please make sure to ask your vet first, especially if you plan to mix different herbs or a herb with medication.
Also, I think ready-made mixes like Oxbow Natural science tabs are useful, since they're already offering a good balance of ingredients and nutrients.