Headbutt tree

Headbutt trees are special trees found in the Johto and Kanto regions that a Pokémon can use Headbutt on to encounter wild Pokémon. They are only found in the games that feature Johto: Pokémon Gold, Silver, and Crystal and Pokémon HeartGold and SoulSilver.

This article is incomplete.
Please feel free to edit this article to add missing information and complete it.
Reason: Generation IV mechanics

Generation II

Headbutting a tree in Generation II

This section is incomplete.
Please feel free to edit this section to add missing information and complete it.
Reason: Confirm that formulas/algorithms apply to both Gold/Silver and Crystal (and not only to one)

In Generation II, most outdoor areas contain a number of special trees () that Pokémon can use Headbutt on. These trees are distinct from other trees that either take up two vertical paces or that have rounded tops. When a Pokémon uses Headbutt on a tree, a wild Pokémon may drop out of the tree. Depending on the time of day, the Pokémon that falls out may be asleep. Some Pokémon can only be caught by this method (e.g., Pineco, Heracross).

All headbuttable trees contain wild Pokémon, but different trees have different chances of creating an encounter after Headbutt is used. The headbuttable trees in an area also generate their encounters from different sets of Pokémon depending on whether they have moderate encounter chances or low encounter chances. For example, on Route 44, trees with moderate encounter chances may only contain Spearow or Aipom, while trees with a high encounter chance may also contain Heracross.

Encounter mechanics

The encounter rate and encounter table of each tree depends on the tree's index and the player's Trainer ID number.

The tree's index is an integer from 0 to 9, which depends on its X and Y coordinates on the map—that is, its distance from the westernmost and northernmost edges, respectively. Specifically, the tree's index is calculated using the following formula.

TreeIndex=\left\lfloor {\frac {X\cdot Y+X+Y}{5}}\right\rfloor {\bmod {1}}0

The encounter rate and tree type depends on the last digit of the player's Trainer ID.

If a tree's index is equal to that ID digit, the tree is a "high-encounter tree" and its encounter rate is 80%.
If the tree's index is one of the next four indices after that ID digit (wrapping back around to 0 after 9), the tree is a "moderate-encounter tree" and its encounter rate is 50%.
Otherwise, the tree is a "moderate-encounter tree" and its encounter rate is 10%.

Encounter rate by index and Trainer ID

The following is a table depicting the encounter rate of the tree, based on the tree index and the last digit of the player's Trainer ID. Tree indexes are displayed in rows, while Trainer ID digits are displayed in columns.

An 80% encounter rate indicates the tree is a "high-encounter tree". Otherwise it is a "moderate-encounter tree".

	0	1	2	3	4	5	6	7	8	9
0	80%	10%	10%	10%	10%	10%	50%	50%	50%	50%
1	50%	80%	10%	10%	10%	10%	10%	50%	50%	50%
2	50%	50%	80%	10%	10%	10%	10%	10%	50%	50%
3	50%	50%	50%	80%	10%	10%	10%	10%	10%	50%
4	50%	50%	50%	50%	80%	10%	10%	10%	10%	10%
5	10%	50%	50%	50%	50%	80%	10%	10%	10%	10%
6	10%	10%	50%	50%	50%	50%	80%	10%	10%	10%
7	10%	10%	10%	50%	50%	50%	50%	80%	10%	10%
8	10%	10%	10%	10%	50%	50%	50%	50%	80%	10%
9	10%	10%	10%	10%	10%	50%	50%	50%	50%	80%

Analysis

Since X and Y are interchangeable in the tree index formula, it is possible to "fix" one dimension to consider traveling along the other. Substituting "Z" for the fixed axis and "n" for the axis that will be traversed, the formula becomes:

{\begin{aligned}TreeIndex&=\left\lfloor {\frac {Z\cdot n+Z+n}{5}}\right\rfloor {\bmod {1}}0\\&=\left\lfloor {\frac {(Z+1)\cdot n+Z}{5}}\right\rfloor {\bmod {1}}0\end{aligned}}

This result shows that, if a single row or column of trees is traversed, moving to an adjacent tree increases the tree's index by ${\textstyle {\tfrac {Z+1}{5}}}$ (modulo 10), where Z is the distance of that row or column from its origin edge (north or west). This means that the closer a row or column is to the edge, the slower the indices of those trees change as the row or column is traversed.

Pokémon Gold and Silver

Wild Pokémon encounters from headbuttable trees in Pokémon Gold and Silver fall into two simple groups.

Azalea Town, Ilex Forest, Lake of Rage, Route 26, 27, 34, 35, 36, 37, 38, 39

Pokémon

Games

Location

Levels

Rate

Moderate-encounter trees

	Caterpie

G

S

C

Headbutt tree

Generation II

Encounter mechanics

Encounter rate by index and Trainer ID

Analysis

Pokémon Gold and Silver

Pokémon Crystal

Generation IV

Pokémon found through Headbutt

Post-National Pokédex only

External Links