Are there any substitute herbal medication for hypertension?

Not really. Most herbals are mild versions of the perscription treatment. Herbals are not regulated .Contrary to common beliefs herbals do have side effects and can interact with other meds.Make sure you tell your doctor if your on an herbal. I know it sounds better to most of us to be on an herbal rather than a perscription but would you eat mold for your strep throat or use penicillin?
Herbs for HBP. Garlic, ginger, ginkgo biloba, buckwheat. Dandelion is a diuretic, which will help. Rhemannia, chinese herb is also helpful. There are many others. Consult a good herbalist in the bay area. There's a plethora here. Chinatown in oakland or sf is a good place to start.
HBP. Ginkgo biloba (above)- enhances circulation and may lower pressure, garlic has long been used for this, as well as ginger. European mistletoe is also recommended, and buckwheat. There are more, including dandelion tea as a diuretic.