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.

## 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.

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

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:

{\displaystyle {\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

#### Pokémon Gold and Silver

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

Pokémon     Games     Location     Levels     Rate
Moderate-encounter trees
G S C 10 65%
G S C 10 15%
G S C 10 5%
G S C 10 65%
G S C 10 15%
G S C 10 5%
G S C 10 15%
High-encounter trees
G S C 10 50%
G S C 10 5%
G S C 10 50%
G S C 10 5%
G S C 10 15%
G S C 10 30%
A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.

Pokémon     Games     Location     Levels     Rate
Moderate-encounter trees
G S C 10 80%
G S C 10 20%
High-encounter trees
G S C 10 50%
G S C 10 20%
G S C 10 30%
A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.

#### Pokémon Crystal

In Pokémon Crystal, wild Pokémon encounters from headbuttable trees fall into six different groups.

Pokémon     Games     Location     Levels     Rate
Moderate-encounter trees
G S C 10 65%
G S C 10 15%
G S C 10 20%
High-encounter trees
G S C 10 50%
G S C 10 20%
G S C 10 30%
A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.

Pokémon     Games     Location     Levels     Rate
Moderate-encounter trees
G S C 10 5%
G S C 10 5%
G S C 10 50%
G S C 10 10%
G S C 10 30%
High-encounter trees
G S C 10 15%
G S C 10 5%
G S C 10 15%
G S C 10 5%
G S C 10 60%
A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.

Pokémon     Games     Location     Levels     Rate
Moderate-encounter trees
G S C 10 15%
G S C 10 20%
G S C 10 65%
High-encounter trees
G S C 10 20%
G S C 10 50%
G S C 10 30%
A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.

Pokémon     Games     Location     Levels     Rate
Moderate-encounter trees
G S C 10 15%
G S C 10 20%
G S C 10 65%
High-encounter trees
G S C 10 20%
G S C 10 50%
G S C 10 30%
A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.

Pokémon     Games     Location     Levels     Rate
Moderate-encounter trees
G S C 10 20%
G S C 10 50%
G S C 10 15%
G S C 10 15%
High-encounter trees
G S C 10 20%
G S C 10 50%
G S C 10 30%
A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.

Pokémon     Games     Location     Levels     Rate
Moderate-encounter trees
G S C 10 80%
G S C 10 20%
High-encounter trees
G S C 10 50%
G S C 10 20%
G S C 10 30%
A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.

## Generation IV

In Pokémon HeartGold and SoulSilver, Pokémon are not grouped by terrain, but now appear in specific locations. Unlike Generation II, not all trees will guarantee an encounter with a wild Pokémon. However, if a tree does cause a wild Pokémon to appear, there is a high chance of encountering a Pokémon again next time. Likewise, if no Pokémon appears when a tree is Headbutted, no Pokémon will ever appear for that tree. Repel cannot prevent Pokémon from appearing when headbutting a tree.

Also, the available Pokémon differ from tree to tree, as illustrated below.

An example of the population of two trees in Pewter City
Tree 1
Pokémon Levels
Hoothoot 2-9
Pineco 2-11
Wurmple 3-6
Tree 2
Pokémon Levels
Hoothoot 10-19
Wurmple 5-8

For example, a tree in Pewter City may house Hoothoot, Pineco and Wurmple, while another in the same locality may house only Hoothoot and Wurmple. The level ranges may also differ for the same Pokémon. As such, not all Pokémon may be found in one tree within a specific location; the (Pewter City) table only reflects the lowest and highest possible level of all Pokémon found in the entire location.

This also explains why some Pokémon can only be found in a specific tree within that location (e.g. Starly in Pewter City or Taillow in Cherrygrove City). These trees are usually hidden, or only accessible via an HM move like Surf or Rock Climb.

Pokémon     Games     Location     Levels     Rate
HG SS 3-5
25-28
10%
50%
HG SS 6-8
25-28
10%
30%
HG SS 3-5
25-28
10%
50%
HG SS 6-8
25-28
10%
30%
HG SS 2-8
11-20
21-30
50%-80%
HG SS 17-19 15%
HG SS 2-25
28-32
20%-65%
HG SS 24-30 15%
HG SS 2-19
21-34
50%-80%
HG SS 5-7
6-8
5%
10%
HG SS 3-7
11-19
21-27
31-32
10%
30%
HG SS 3-7
11-19
21-27
31-32
10%
30%
HG SS 39-43
42-48
20%
HG SS 3-8
13-16
21-27
39-48
20%-30%
HG SS 2-17
28-29
30%
HG SS 2-5
11-17
21-30
39-48
20%-50%
Pokémon appearing in only one location
HG SS 3-5 30%
HG SS 3-5 30%
HG SS 5-7 10%
HG SS 5-7 10%
A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.

#### Post-National Pokédex only

Pokémon     Games     Location     Levels     Rate
HG SS 2-10
21-30
20%
65%
HG SS 10-20
26-30
20%
65%
Pokémon appearing in only one location
HG SS 3-7 30%
HG SS 3-7 5%
HG SS 18-25 35%
HG SS 3-7 5%
HG SS 3-7 30%
HG SS 10-18 35%
HG SS 5-12 35%
HG SS 18-25 35%
HG SS 18-25 35%
A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.