In "How to Live Forever: The Enduring Power of Connecting the Generations," author Marc Freedman recalls a story drawn from the Talmud and told at a memorial service for his father.

"It tells the story of a rabbi passing through a field, noticing an old man planting an acorn. 'Why are you planting that acorn?' the rabbi asks, in what I imagine is a scoffing tone. 'You surely do not expect to live long enough to see it grow into an oak tree.' To which the old man — turning slowly from the ground to fix his glance on the not-so-wise clergyman — says, 'My ancestors planted seeds so that I might enjoy the shade and the fruit of trees. I do likewise for those who come after me.'"

Other versions use a different tree, but the message is the same: "Planting, tending, bequeathing to the next generation — it's the essential human project, one we've understood yet let slip over the past half century," writes Freedman, founder of the social enterprise "It is our role as older people to plant those trees under whose shade we shall never sit. Out task is not to try to be young, but to be there for those who actually are."

Thinking about legacy involves acting on critical end-of-life practicalities. A report by the demographic consulting firm Age Wave and the financial services company Edward Jones notes that only 32% of those surveyed who have been retired for 15 years or more have a will, power of attorney and healthcare directive. Less than half have discussed legacy plans with loved ones.

"While retirees agree that memories, values and life lessons are the most important things to pass on, only 17% have created documents or resources for this purpose," write the authors of "Longevity and the New Journey of Retirement." Take the time to talk over and document your legacy for family and extended family.

Legacy extends beyond immediate circles of love. The Census Bureau predicts that by 2034 there will be more people 65 years and older than under the age of 18.

In the Age Wave/Edward Jones report, 77% said they feel a responsibility to help future generations. The older generation has an unprecedented opportunity and responsibility to plant seeds now for younger generations.

How will you take your accumulated experience and knowledge to help society's younger generations navigate life smarter and better? That's a legacy challenge to embrace.

Chris Farrell is senior economics contributor to American Public Media's "Marketplace" and a commentator for Minnesota Public Radio.