PODZOL

No villager with a profession touches podzol. The Wandering Trader is the only one who sells it, when his stock happens to include it, at 3 emeralds for 3, drawn from his uncommon stock rather than his everyday offers.

It has no crafting recipe, a forest floor near an old growth tree is the only place to find it directly. Mining a placed block with an ordinary tool gives back plain dirt instead, only Silk Touch keeps it as podzol.

The Wandering Trader sells podzol for 3 emeralds for 3 out of his uncommon stock, when that stock happens to include it. He does not buy podzol back off a player either, the offer only ever runs one way. No standard village profession lists podzol in its trade table at any tier, so this one roaming merchant is the whole market for it.

He asks 3 emeralds for 3, which works out at 1 emerald each, and 39 of the other 75 come cheaper. Price is the easy part: he draws a rare slot from a shared pool, so catching one that happens to be carrying podzol is the real constraint.

The Wandering Trader asks 3 emeralds for 3 podzol. 8 of the 72 villagers that pay emeralds, emptied out:

3 diamonds against 78 flint for the same 3 emeralds, 26 times the carrying, and the shortest wait is the Leatherworker at 1.9 real minutes of shelf, gathering not counted.

The Wandering Trader is not part of any village. He arrives near wherever a player is playing on his own schedule, trailing his usual pair of leashed llamas, and eventually wanders off again whether or not a trade happened. There is no workstation to place and no job block to break, so the usual tricks for steering a regular villager toward a particular offer, curing a zombie villager, breaking and replacing a workstation, do nothing for him.

He does not buy podzol off a player, only sells it, so the offer runs one direction: emeralds out of an inventory, podzol into it. His stock for that visit, up to 6 podzol if the uncommon-pool roll included it, is everything that offer will ever give before he moves on for good.

Each trader carries only a slice of his full stock list, so the one standing in front of a player may simply not have podzol that day. Waiting for another one means another independent roll of the whole pool, the same odds each time. Naming him with a name tag stops him from despawning, turning a passing merchant into a shop a player can keep coming back to instead.

Landscaping a large area is the only real reason to buy podzol rather than gather it: a forest floor near an old growth tree hands it over for free, no emeralds and no waiting on a trader whose rare-pool stock is still a coin flip either way.

Bring Silk Touch along either way. Mining a placed podzol block with an ordinary tool drops plain dirt instead, the same rule that governs the trade's own sibling, Rooted Dirt, which needs no such tool.

Also on the Wandering Trader's list: potion of invisibility, acacia log, birch log, dark oak log, jungle log and oak log.

Podzol generates in old growth taiga, and the giant spruce trees that stand there make more of it: when one of those trees grows, the ground around its trunk turns to podzol on its own. That makes a spruce sapling farm the only renewable source of it in the game.

What makes the block worth having is what it lets you plant. Mushrooms placed on podzol stay put at any light level, where on ordinary dirt they pop out of the ground the moment it gets bright. A floor of podzol under a roof is the standard way to farm brown and red mushrooms without building in the dark.

Mushrooms only stay planted in the dark, on almost every block in the game. Podzol is the exception: a mushroom on podzol survives at any light level, in the open, in daylight, which turns a mushroom farm from a dark room into a field.

Mycelium does the same thing and only exists on mushroom islands, so podzol is the version most worlds can actually reach. Bone meal on a mushroom standing on it grows the giant version, which is where mushroom blocks in quantity come from.

It also refuses grass. Podzol does not spread and grass will not spread onto it, so a path or a garden bed laid in podzol stays exactly the shape you built it.