I second that - SteveMobsterG
You need at least 200-300mg daily for about 8-12 weeks for mild-modest reduction in BP.
Realistically, if you already have high blood pressure, get some medication from your doctor man... high BP causes damage - stop wasting your time in the hopes of fixing it.
Highest determinant to blood pressure reduction is weight loss (by far), then smoking cessation, reduced sodium.