Use a comma to separate two adjectives when the adjectives hold equal weight in the sentence. You can be sure you need a comma if the word and can be placed between the two adjectives.
This sentence needs a comma between the adjectives:
The tall, blonde boy is my brother.
The boy is tall. The boy is blonde. The boy is tall and blonde.
Here are more sentences with two adjectives that need a comma between.
Our neighbor has a big, angry dog. The dog is big and angry.
That junky, rusted truck should be towed away. The truck is junky and rusted.
I like the small, curly-haired dog. The dog is small and curly-haired.
Here is an example of a sentence where you do not put a comma between the two adjectives.
The tall pine tree in our yard gives good shade.
The words tall and pine both describe the tree, but we would not say The tree is tall and pine.
Use a comma between two adjectives in a sentence when the word and can replace the comma.
▶It’s your turn. Decide if this sentence needs a comma. That long sad song was depressing. I hope you put a comma between the two adjectives.