01 Prerequisites and the Basic Structure of Tree Farms
1 Prerequisites
This section briefly covers the basics you need before diving into tree farm research. For simplicity, some content here is technically "incorrect." For fuller explanations, see the Update Theory and Timing Theory sections of GTMC.
1.1 Updates
In Minecraft, updates come in two types: NC updates and PP updates.
The main sources of NC updates in tree farms are TT (Tile Tick) components (typically Redstone Repeaters, Comparators, and Observers), Redstone Dust, powered or activated rails *we'll just call these "rails" from here on, since tree farms rarely involve the other two types*, Pistons along with the blocks they push/pull, and Note Blocks.
When these components change state (e.g., becoming powered or activated, or a block changing), they send NC updates to the following:
- Redstone Dust (on energy level change): second-order neighbors
- Repeaters, Comparators, Observers: first the block their output points to, then that block's neighbors (excluding themselves)
- Horizontally placed rails: its own neighbors, then the neighbors of the block below; diagonally placed rails: its own neighbors, then the neighbors of the block below, and finally the neighbors of the block above
- Pistons: neighbors of both the piston itself and the original position of the blocks it pushes/pulls
- Note Blocks: neighbors
These are NC updates and can be detected by BUDs.
Since tree farm structures are mostly made of Pistons, all NC updates in tree farms generally come with PP updates as well. Observers specifically detect PP updates.
In tree farms, pure PP updates (without accompanying NC updates) typically come from:
- Trapdoors/Fence Gates opening or closing
- Dispensers/Droppers/Hoppers changing activation state
- Glass Panes/Fences/Iron Bars/Walls changing connection state
In the wireless redstone section, we'll cover three important signal transmission methods: tree power (through leaves, transmitting NC and PP updates), scaffolding power (through scaffolding, transmitting NC and PP updates), and wall power (through walls, vertically transmitting PP updates). Taking advantage of their properties can greatly simplify wiring in tree farms. More details will be in the wireless redstone special topic.
1.2 Timing
In Minecraft, timing comes in two forms: inter-tick timing and intra-tick timing.
Each second is split into 20 game ticks, or gt (we won't explain the concept here). Some components have fixed macroscopic delays, such as Repeaters (2-8gt), Comparators and Observers (2gt).
Apart from TT components, other components used in tree farms generally have no macroscopic delay.
Each gt is further divided into multiple phases that execute different operations. The phases most relevant to tree farms, in order of execution, are:
- Tile Tick (TT) -- TT component operations run here
- Block Event (BE) -- Piston and Note Block operations run here
- Entity Update (EU) -- entity-related calculations (vehicles, mobs, etc.) run here
- Tile Entity (TE) -- Hopper operations and blocks being pushed/pulled by Pistons run here
- Async Task (AT/NU) -- player-related calculations run here
Apart from the components listed above, instant components execute their operations immediately upon receiving an update, regardless of which phase the update is in. Common instant components include Redstone Dust and rails, Fence Gates and Trapdoors, Note Blocks, Droppers and Dispensers.
The execution order of TT components depends on macroscopic timing, TT priority, and sub-order. In practice, TT components execute in this order:
Any Repeater >= Comparator pointing to a Comparator > general Comparator or Observer
BE components (Pistons and Note Blocks) execute in the order they receive updates and confirm a state change is needed. This ordering is sometimes called depth. Note Blocks do not increase depth (i.e., they don't delay the execution of the components they update within BE).
When analyzing timing, look at macroscopic timing first, then which phase the operation falls in, and finally the execution order within that phase.
In tree farms, each Piston action (push/pull/0t) takes 3gt by default. Piston actions triggered by 1gt and 2gt powering take 4gt and 5gt respectively.
2 Basic Structure of Tree Farms
From Minecraft 1.15 onward, a tree farm's basic structure consists of:
- Bonemealing
- Trunk processing (sometimes split into main trunk processing and root processing)
- Leaf processing
- Sapling recycling
- Block-to-drop conversion
Most tree farms also include a detection module that detects sapling growth and triggers the farm, but this isn't required. We'll cover it in the next chapter.
In Minecraft 1.14 and below, jungle and acacia trees have special growth detection requirements, so tree farms sometimes need a height increase module. Spruce trees require no logs in a 5x5 area to grow, which means a retractable wall is needed. This article focuses on 1.15+ tree farms, so we'll skip these cases for now.
2.1 Bonemealing
Typically, Dispensers fire Bone Meal onto saplings.
Since Dispensers hold very little Bone Meal, it's usually fed in through Hoppers or Droppers, with an unloader transferring Bone Meal from Shulker Boxes into the Hopper or Dropper chain.
2.2 Trunk Processing
Main trunk processing is straightforward: move the trunk away from where it grew. The basic approaches are triple push extension and pseudo double push extension. For birch and oak, a simple push/pull setup works fine.
Triple push extension:
Pseudo double push extension:
Honey-slime wall double push extension:
Retraction-type pseudo double push extension (a design where the secondary Piston only performs retraction (0t), shaving one Piston action off the timing):
The most widely used design today is honey-slime wall double push extension.
Root processing generally has four approaches: processing alongside the main trunk, upward push, downward pull, and side pull.
Upward push:
Downward pull:
Side pull:
For dark oak, an upward pull method is sometimes used.
2.3 Leaf Processing
Also straightforward: use Pistons or honey-slime walls to push away enough leaves to get the saplings you need.
Honey-slime wall:
Piston:
Each leaf block has a fixed chance to drop a sapling: jungle 1/40, all other tree types 1/20.
2.4 Sapling Recycling
Saplings dropped by the leaf processing module are collected near the player using Hoppers, water flow, or similar methods.
Hopper:
@Scorpio 天蝎君 4gt birch
Water flow:
@Feng_Bl, Sunflower_Lin 6gt birch
In tree farms with fast processing cycles and tight internal space, Hopper Minecarts are sometimes used for sapling recycling.
@Qonctrol, PUTF sharp
2.5 Block-to-Drop Conversion
There are two main methods: Wither and TNT.
Wither:
@Scorpio 天蝎君, PUTF flat wither
TNT:
@Feng_Bl