Daybloom

The flower only opens while the sun is up, and an open one is the only version worth cutting. A closed stem gives you the herb and nothing more. Cut it with the yellow head showing and seeds come with it, which is what lets a patch pay for itself. Swing a Staff of Regrowth or an Axe of Regrowth instead of a sword and the seed yield jumps far enough that one wild cluster can stock an entire planter setup.

It takes ordinary grass and hallowed grass, so a surface farm keeps working after the world turns and the hallow creeps into it. Clay pots and planter boxes both accept the seeds. Growth runs faster during daylight, which lines up conveniently with the fact that you want to harvest in daylight anyway. Angry Dandelions drop it, and herb bags can contain the flower or the seeds.

Researching every herb by hand is a slog. Research a single Garland instead, duplicate it, then run the copies through shimmer to break them back into components. The herbs come out the far end without you ever farming full research stacks.