Also on Sunday, Prince William's children wrote handmade cards to "granny" Diana on Mother's Day

Prince Harry is honoring his late mother, Princess Diana, on Mother's Day in the U.K.

PEOPLE confirms Harry, 36, arranged for flowers to be placed at Princess Diana's grave in Althorp, Northamptonshire, in honor of the annual holiday, which is known as "Mothering Sunday" and celebrated in the United Kingdom this year on March 14.

Harry was 12 when his mother died in 1997. His brother Prince William, who is a patron of Child Bereavement UK, was 15.

This summer, Harry, who lives in California with his wife Meghan Markle and their son Archie, hopes to make it back to the U.K. for the long-awaited unveiling of the statue to his mother, Princess Diana, that's taking place at Kensington Palace in July, those close to him say. However, no travel arrangements have been solidified.

Last year, Meghan and Harry celebrated Mothering Sunday with a sweet post on their now-closed Instagram page. The photo showed a number of different names for mothers and grandmothers, including "mum," "mama" and "granny."

"No matter what you call your mum, this Mother's Day in the UK, we honour the mums all over the world who do so much every single day, and now more than ever," they captioned the post. "Thank you."

And in May 2019, shortly after Archie's birth, Meghan and Harry shared a sweet photo of Meghan holding her son over a field of flowers to mark the Duchess of Sussex's first Mother's Day.

Dianas GraveCredit is to Jonathan Beech. These were taken on June 21st 2017.
Credit: Jonathan Beech

Also on Sunday, William celebrated their late mother by sharing photos of a trio of handmade cards from his children Prince George, 7, Princess Charlotte, 5, and Prince Louis, 2. "This year Mother's Day will be different once again. Many of us will be apart from our loved ones, but looking forward to a time in the not too distant future when we can give our mother a hug again. But for those experiencing bereavement, today may be particularly challenging. Each year on Mother's Day, George, Charlotte and Louis make cards remembering their Granny, Diana, for William. Whatever your circumstances, we are thinking of you this Mother's Day," a post on the Kensington Palace Instagram account read.

"Dear Granny Diana, Happy Happy mothers day. I love you very much and think of you always. Sending you lots of love," George wrote on his card while Charlotte wrote: "I am thinking of you on mothers day. I love you very much. Papa is missing you. Lots of love."

prince harry, princess diana
Prince Harry and Princess Diana
| Credit: John Shelley Collection/Avalon/Getty

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During Meghan, 39, and Harry's interview with Oprah Winfrey, he spoke about what his mother would think about his exit from royal life. "I think she saw it coming," he shared. "I certainly felt her presence throughout this whole process."

Meghan and Harry announced on Valentine's Day that Meghan is pregnant with their second child. During their sit-down interview with Oprah, they shared the news that they are expecting a girl.

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Soon after. photographer Misan Harriman shared a new maternity photo of the growing family.

"What wonderful news to celebrate on International Women's Day! Congratulations my friends, and welcome to the #girldad club H," the photographer captioned the sweet snap.