Days to maturity are from date of transplanting, not seeding.
Artichoke is a biennial, and in the north the young plant must be tricked into thinking it has already gone through a season of growth and a winter, a process called vernalization. Start indoors in mid-February and grow on at warm temperatures (at least 60°) avoiding direct hot sun or overwatering (misting is preferred). Transfer after 6 weeks to a cold frame when outdoor temperatures stay above 25°. Keep as cool as possible over the next 6 weeks without going below 25°. Then, set out about 3' apart, feed heavily and give lots of moisture and space (10 sq ft per plant). IRT plastic mulch
and/or row covers
can be helpful to hasten maturity.