Disclaimer: Still searching for the parallel universe where I own Naruto and Kishimoto is sitting in Kuwait typing on his laptop.
X is for Xeranthemum. N'oubliez jamais.
Infused with his chakra, the cherry blossom tree and the bright flowers never wilted. While the tree was an obvious connection to Sakura-chan, the Xeranthemums weren't unless you knew their meaning.
Eternity. Never-fading remembrance.
Naruto's regeneration saved him repeatedly but also halted his aging. He still looked twenty-five. It was over 250 years since he had happily settled down with his Sakura-chan. When she died, her only regret was not having children. Naruto was secretly torn between sadness and relief. (After all, outliving your children sucks.)
With his eternal garden he kept Sakura-chan's memory alive. He would never forget her.
A/N: Not that I necessarily believe this is how his regeneration works, but it's certainly a possibility. At least it's more realistic than the damage from a Rasen-Shuriken being beyond Naruto and Kyuubi's power to heal in my opinion. One more to go...but considering my awesome math skills that's an awfully flexible number...