Monday, Aug. 31, was the 23rd anniversary of Princess Diana's tragic death in a car crash.

On the solemn day, Prince Harry and Meghan Markle paid a visit to the Preschool Learning Center in Los Angeles, where they spent time with children and got involved in garden work in the classroom. But the Duke of Sussex had also come prepared to honour his late mother's anniversary.

Prince Harry honours Princess Diana on 2020 death anniversary

The main event during the school visit was to replant the preschool's classroom garden. And, according to People, Prince Harry had brought seeds of Forget-Me-Nots — known to be a favourite of Princess Diana — which he planted to mark the 23rd anniversary of his mother's passing.

On Tuesday, the Assistance League of Los Angeles, which runs the Preschool Learning Center, shared photos of Harry and Meghan's "wonderful surprise" visit to the school.

In the photos, Harry and Meghan are seen getting hands-on in the garden and giving the young gardeners a few pointers. The AL added that the Sussexes shared their "appreciation for nature" and helped "instill the importance of healthy eating" in the children during the visit.

Princess Diana's birthday in 2021 to receive unique honour

Princess Diana's brother Charles Spencer also marked the anniversary of her death with a social media tribute on Monday. Late last week, it was further announced that Prince Harry and Prince William commissioned a statue of their late mother that will be unveiled on July 1, 2021—what would have been her 60th birthday.

Meanwhile, Harry and Meghan's visit to the L.A. preschool continues their back-to-school season community work. In late August, they also stepped out to assist with a school supplies distribution with Baby2Baby charity.