The aging process itself can cause a stiffening of the blood vessels; also our genes, etc. In general, for people with hypertension, more potassium is better. One might use a salt substitute, like "Morton's Salt Substitute", which is potassium chloride. Or drink low sodium v-8 juice, which is high in K. One might also take Magnesium citrate, or Mg-taurate supplements; according to label. One might also take a garlic supplement like Garlicin HC (TM) according to label instructions, or another good garlic supplement (e.g. Kwai). If one likes celery, this makes a good snack! And the general advice still applies: report all supplements you take to your doctor when you visit.
P.S. If a person has pre-existing kidney disease, they should consult a doctor before beginning to supplement potassium and/or magnesium.
Studies etc. K https://www.ncbi.nlm.nih.gov/m/pubmed/21403995/
Celery: https://www.ncbi.nlm.nih.gov/m/pubmed/25352064/ Also: https://www.google.com/amp/s/health.clevelandclinic.org/celery-may-help-bring-your-high-blood-pressure-down/amp/ There is a lot more interesting stuff on the web about celery and other than just this. This study addresses the kidneys, high bp is not good for the kidneys over time.
There is plenty of quality material on the net regarding K, mg, celery and garlic to aid control of hypertension.
NB: Of course, those with hypertension, even mild hypertension, should be under the care of a doctor and as I said above, the doctor should be informed of the supplements one takes.