patches-own is a special NetLogo keyword that allows us to define characteristics that belong exclusively to the patches in a model. These characteristics are variables that have a unique value for each individual patch. patches-own is helpful in modeling environmental variables. For example, if we wanted to create a model of pollution where a factory would pollute the patches immediately near them:

patches-own [pollution]
create-turtles 1 [
    set shape "factory"
    ask patches in-radius 3 [
        set pollution 100
    ]
]

Things to keep in mind when using patches-own:

• We can define as many variables as we want within patches-own such as patches-own [water nutrients heavy-metals altitude] by separating each variable with a space.
• A turtle can access a characteristic of its current patch directly. For example, ask turtles [set pollution 100] does the same thing as ask turtles [ ask patch-here [set pollution 100] ].

In the model example below, we are modeling a garden with flowers. We define a nutrients characteristic for our patches and assign each patch a random number of nutrients between 0 and 10. We also change each patch's pcolor according to its nutrient level so that a darker patch indicates higher nutrient levels. Finally, we sprout a flower on each patch. Initially, each flower has the same size but when the go button is clicked, each flower grows according to the nutrition level of their patch.