I was asked to turn my comments under the question into an answer.
In this case, what's being described can either be a tall green pole or it can be a tall, green pole.
It depends on how the pole is being interpreted and described.
With this kind of adjectival use, one modifies another that follows it. They are cumulative because each adjective modifies the adjectival phrase that follows.
Say you are standing in a field of poles, and all of them are green. Also, every pole you've seen so far has been short.
Suddenly, you spot a green pole that happens to be tall:
"Look! It's a tall green pole.
In this case, the items being described are considered to be "green poles", and tall serves to modify that thing. In other words, you have this:
tall green pole
→ tall [green pole]
→ "That green pole is tall."
With this type of adjectival use, each adjective modifies the noun independently of anything else.
At a different time, you could be walking down the street and see a pole. You observe that it's tall. You also observe that it's green.
As far as you're concerned, the fact that it's tall has equal important to the fact that it's green—they are two separate items of interest.
You might say this:
"Look! It's a tall pole. Oh, and it's a green pole too."
→ "Look! It's a tall pole, and it's a green pole."
→ "Look! It's a tall and green pole."
→ "Look! It's a tall, green pole."
This method of replacing the conjunction (and) with a comma is the same method that's normally used in other expressions:
"I ate apples and I ate oranges and I ate pears."
→ "I ate apples, oranges, and pears."
The comma stands in for and, as well as serving to help break up the list items visually. (In speech, it might also indicate a slight pause between the items.)
The one thing that's different about normal expressions is that we use an and before the final list item. That is not the case with coordinate adjectives.
Getting back to the pole, in this case, there is a "pole" that is both tall and green:
tall, green pole
→ tall, green [pole]
→ "That pole is both tall and green."