Plants

Nothing grows on a timer. Every tick the game picks a batch of random tiles and asks each one whether it wants to do something: spread grass, extend a vine, sprout an herb, mature a tree. The batch size is world width times world height times an update rate times a time rate, so bigger worlds get proportionally more updates and growth per tile stays roughly constant.

The world is split into two pools. Everything above the surface line draws surface updates and everything below draws underground ones, and a tile only pulls from its own pool.

The time rate is the lever you control. It sits at 1 normally. Sleeping in a Bed sets it to 5, which is the best thing you can do while waiting on herbs or a tree farm. In Journey Mode the time speed slider pushes it further, up to a hard ceiling of 24, and freezing time stops updates altogether.

One trap. Skipping ahead with an Enchanted Sundial or an Enchanted Moondial forces the time rate back to 1 and ignores every other modifier. It moves the clock but it does not grow anything, which is the opposite of what most people assume when they build a herb farm and then sundial past a week of it.

Rain is a free boost: surface tiles update 50 percent more often while it falls.

The seven herbs carry potion crafting, brewed over a Placed Bottle or at an Alchemy Table. Wild sprouts use their own routine rather than ordinary tile updates, tuned so world size barely matters: bigger worlds run more attempts at a lower chance each.

Harvesting one while it is blooming is the whole game, because only a bloomed plant returns seeds alongside the herb. Daybloom wants daytime and Moonglow night; Deathweed needs a blood moon or full moon, Waterleaf needs rain, Fireblossom wants a clear late afternoon, Shiverthorn blooms as it grows and Blinkroot at random. Planter boxes keep all seven within reach of one bottle.

The rare plants all use the same anti-clustering check: nothing spawns if another of its kind already sits inside a square centered on the target tile. Those squares are large. Dye plants block each other across 181 tiles, Life Fruit across 121, Plantera's Bulbs across 301 and Strange Plants across 481. Per valid update the odds run about 1 in 3000 for a dye plant, 1 in 15000 for a Strange Plant, and roughly 1 in 1000 for a Life Fruit or Bulb.

So farms have to be long, not dense. Packing planting space into a small room does nothing here; extending a corridor sideways for a few hundred tiles does. It is also why Strange Plants trickle in so slowly, and why collecting every Dye Trader reward is a long-term project.

Both want two flat neighboring tiles of Jungle grass below the surface line, and both destroy other jungle plants to clear room. Flat ground is the bottleneck, since an untouched Jungle is mostly slopes and broken edges. Mine long horizontal tunnels down there and leave Jungle grass as the floor, and the rate climbs sharply, because you have manufactured thousands of valid tiles.

Life Fruit appear once any mechanical boss is dead and glow under a Spelunker Potion, the fast way to sweep a tunnel network. Bulbs need all three mechanical bosses down, and one is placed automatically when the last dies, opposite the Dungeon.

Treat a Bulb carefully. Mining it, blowing it up, spraying it with a Clentaminator or hammering the grass beneath it all summon Plantera where you stand. Weapons cannot break one, so a stray shot is safe; a stray pickaxe swing is not.

Most plants refuse to grow if a background wall occupies the soil tile or the tile above it. The exceptions are the grass, jungle, flower and mushroom walls plus every fence in the game, and that is what makes an enclosed farm possible: put a Wooden Fence behind the whole area and you get full wall coverage against enemy spawns while plants carry on normally. Painted grass passes its color to whatever grows on it, so think before painting the floor of a dye farm.

Vines hang from grass and reach ten tiles given room. Cutting one tile takes everything below it, and mining the block it hangs from removes the lot. Jungle vines count toward the Jungle's biome requirements while corrupt, crimson and hallowed vines do not, though they still infect neighboring ground. Pick up the Guide to Plant Fiber Cordage and they start yielding Vine Rope. The Vine hook is unrelated and drops from Man Eaters.

Thorny bushes hurt on contact and cannot be collected, and the Corruption and Crimson kinds create their own biome grass on adjacent dirt, which is a quiet failure point in quarantine trenches. Sunflowers do the opposite, blocking spread on the tiles they occupy and giving nearby players a small speed boost with fewer enemy spawns.

Moss grows on underground stone and comes up with a Paint Scraper. Sea oats give Hay to a Sickle. Pumpkins grow wild at Halloween or from Dryad seeds, and are the only source of the Magical Pumpkin Seed.