AARP, a national organization that offers services and support to older citizens, has named Watertown-based Tufts Health Plan as one of the 50 best places to work in America for people who are 50 years old and up, officials announced recently. AARP said the Mount Auburn Street company welcomes older employees, noting that more than a third of Tufts Health Plan employees are 50 or older, and the average tenure of employees in that age group is 11 years. The company also offers a wide range of services and support for older employees, such as an on-site clinic providing wellness coaching, preventive and symptom care, and lab services, AARP officials said. Tufts Health Plan also has programs in place giving counseling to workers living with aging parents, helping search for elder care services, and providing legal and financial consultations. All employees are offered flu shots, programs to quit smoking, gym discounts, stress management training, massage therapy, free monthly nutritional seminars, and an annual wellness fair. According to AARP officials, 90 percent of Tufts Health Plan employees used at least one of these wellness benefits during a recent yearlong period. For more information, visit www.aarp.org or www.tuftshealthplan.com.