Tarragon (herb) is classed perennial in the cited extension guidance. The timing rules below are relative to your local freeze dates — enter a location to turn them into calendar dates.
The rules this site applies
Method
Frost-relative window
Rule & reconciliation
Transplant outdoors
from the median last spring freeze to 2 weeks after
USU Extension says to transplant French tarragon in the spring after the last frost so the tender young shoots survive, a point rule that opens a two-week planting span at the last spring freeze.
Variety assumption: Assumes French tarragon, which Virginia Cooperative Extension says can only be propagated asexually — seed-grown plants are the flavourless Russian type — so no seed-sowing window is given.