Licorice, ginseng and ephedra are all known to raise blood pressure. Caffeine should also be avoided. Most people reading these items would think that they would be easy to avoid but it's not as easy as you think. Many herbal teas contain licorice or ginseng in them as these are considered stimulants and are great for a little boost in your non-caffeinated herbal tea. Caffeine exists in certain medications such Excedrin and ephedra makes and appearance in some energy drinks (which I don't recommend you drink anyway).
If you have high blood pressure always be sure to check with your health care professional to keep it under control but in the meantime be aware of those foods that can undermine your efforts.