I don't know a lot about BP cos mine is so low I'm deemed an anomaly. ( 80/40 when I came out of surgery. [Checked by three different machines].) However, Mrs R has high BP but will not take medication.
Her massive supply of vegetarian and health books have recently come up with the data for eating celery. The claims are astounding, and if true, it is probably working by relaxing the blood vessels, and may therefore allow the body to ‘re-datumize'. i.e. you would have to keep taking more and more.
Since celery is not unpleasant, why not give it a try?