Tarragon (Artemisia dranunculus) is a cold hardy perennial herb native to our area. Here is its entry in the Montana Field Guide. It truly has a really delicious flavor and we use it on pizza, roasted chicken and veggies, soups and pastas, etc.
It grows in a clump, gets 4 to 6 feet tall, and dies back to the ground in the winter.
These are 3rd year root crowns with a bit of stem attached.
Photo credit: Cillas, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons