I have a planter ready to go, and I have a daylily in my inventory. But there’s no option to grow daylily in the planter.
It used to work like this, but a lot of people complained about needing the herbs/seeds, because sometimes you wouldn’t find enough or they would be used for something else first - and it was too difficult to get them - so the system was changed half a year ago to be more similar to the Farming system, where you unlock a certain herb and can always plant them, regardless of having herbs or not
To unlock new plants you need to craft a Herbalist Exploration Garden with your Herbalist and place it down. They’ll do the rest of the work
You can focus the search on native or exotic herbs. Native goes faster but only finds herbs from your own biome (very rarely finding a plant from another biome)
Exotic takes longer but can find and unlock any herb from any biome in the game
So I recommend going with native first just to unlock all the stuff around you - and then switch to exotic!