Beets or beet juice. Or possibly other vegetables with high nitrate content, green leafy ones like kale.
Beet juice is proven (many studies) to reduce high blood pressure, most studies say about 10 points. Does not lower normal blood pressure. I'm not sure what level is "high" for this purpose.
Mechanism is nitrate in the veg in converted to nitrous oxide which dilates blood vessels hence reducing pressure. Not a permanent or lasting effect, so you'd have to eat/drink it daily. But it's very good for you too. Quantity used in the studies ranged from 8 to 16 oz of juice.
Another natural way is to lose weight. Mechanism as I understand it is your body tries to maintain blood in a volume consistent with your weight.
Other things are exercise and the so-called DASH diet. See here:
http://www.nhlbi.nih.gov/health/public/heart/hbp/hbp_low/hbp_low.pdf
I had HBP (150/100) and a high resulting pulse (100) from 30 y/o, took a beta blocker for almost 20 years to hold BP at 140/85 and resting HR at 80. Then lost weight, started getting daily exercise, also changed my diet, and no longer need the beta blocker. BP 135/80 typically, resting HR 55-60.
However, changing my occupation made a big difference too. I took a year off work once, and didn't need meds during that time. Then I dived back into the grind and needed meds again. Currently I work but am perhaps more zen about it than I used to be. Or maybe not. I record my HR and BP occasionally during the day and write it on my whiteboard. Right after I've ridden my bike (fast) to work, it is typically 95 140/90. During the day when nothing is going on it is typically 65 135/80. But I have one reading on the board - I was waiting for a piece of news to be released that would mean either we made or lost money - HR was 64 but BP was 165/100 . . . Stress is tough.