Tall grass

Gold explores the tall grass on Route 29

Tall grass is a mechanic in the Pokémon main series, as by entering patches of tall grass, a wild Pokémon may appear and begin to battle the player. It is the prime habitat for wild Pokémon, much like caves and water.

Tall grass is found on most routes of the Pokémon world, with some routes containing more tall grass patches than others. If the player enters a patch of tall grass, they may randomly enter a wild Pokémon battle. Players are warned by other characters to stay out of tall grass if they don't have a Pokémon due to the possibility of being attacked by wild Pokémon.

In Generation I and Generation III, if Cut was used, the grass adjacent to the player would be totally erased, unlike Generation II, where different styles of grass (such as in National Park) would change into normal grass once Cut was used on them before eventually disappearing. The ability to use Cut on grass was removed in Generation IV.

Technical mechanics

Determining the rate of encounter

The rate of Pokémon encounter is determined from a simple mathematical formula:

1 in (187.5 / ( x )) per step

Let x equal the a value which determines how rare the Pokémon is. The higher the encounter rate, the more common the Pokémon is.

	Encounter-rate table
Encounter Type	Encounter Rate
Very Common	10
Common	8.5
Semi-Rare	6.75
Rare	3.33
Very Rare	1.25

Poké Radar

File:PokéRadarShinyFormula.png

The formula for the probability of finding a shiny Pokémon. N_c is the number of Pokémon in the chain, up to 40.

The Poké Radar is a device introduced in Generation IV that is used to seek out wild Pokémon hiding in long grass. If the Pokémon that is found is knocked out or captured in a Poké Ball, a chain will begin. These chains consist of multiple members of the same Pokémon species encountered one after another. The only catch is this: a player must not encounter any Pokémon just by walking through non-wiggling grass, only by walking into the grass that shakes. Therefore, it is recommended that Repel is used in order to ensure this and achieve a higher chain. Entering the same type of grassy patch the chain was started in that is the farthest away increases the chances of meeting the same kind of Pokémon consecutively. Long chains increase the chance of finding a Template:Shiny2 Pokémon, which is indicated by the patch of grass glowing white twice rather than shaking.

Shiny Pokémon

In Generation III, most of the data structures were redone. As such, a Pokémon's shininess would no longer need to be linked to its stats due to incompatibilities between the previous generations. The determinant for shininess is instead a calculation based on the Trainer ID number of the player encountering it and the personality value of the Pokémon. The same method is used in Generation IV.

The secret ID and Trainer ID bytewords are first xored together, and then the first byteword of the personality value is xored with the second byteword of the personality value. If the xor of these two results is less than eight, then the Pokémon is shiny. This results in a probability of 8 in 65536; simplified as 1/8192 (2^-13, or approximately 0.012207%), just as in Generation II. Symbolically:

(Trainer ID) xor (Secret ID) = E

(First byteword of personality value) xor (Second byteword of personality value) = F

If E xor F is less than eight, then the Pokémon is shiny.

Alternative areas

Long grass

File:Tall-grass.PNG

Long grass on Route 119

Some areas in the Pokémon world have larger patches of grass than usual. These patches of grass have grown longer and more widespread than the usual grass patches, hiding many different species of Pokémon. Because of the length and thickness of the grass, it is impossible to ride a bicycle or run through the patches in Generation III, but one can run through them in Generation IV. Some trainers hide in the long grass patches, concealing themselves from view and surprising the player to a battle. Long grass was introduced in Generation II, where it was found in Johto's National Park. In the third generation it was found on Route 119 and Route 120 in Hoenn, and was also present in Generation IV on Sinnoh's Route 210, among other locations.

Seaweed

File:Dive Hm Lucas.jpg

Patch of seaweed

Seaweed, found only in Generation III, is located underwater in Pokémon Ruby, Sapphire, and Emerald, as an underwater equivalent to tall grass on land. Seaweed can be found while using Dive on dark patches of water on Route 124 and Route 126. The chance of encountering Pokémon in seaweed is lower than that of tall grass.