The couple began its 10-day Diamond Jubilee tour of South East Asia and the South Pacific by finally completing Diana, Princess of Wales' journey to the gardens, 15 years after her death.
The royal was killed in a car crash in 1997 just two weeks before she was due to make the trip to see a white orchid that had been named in her honour, and Alan Tan Chye Soon, manager at the garden, told reporters, "It was so sad that she never saw it... We were getting ready for her to come over when she died. It was like William and Kate are fulfilling her promise today."
When told that his mother never got to see the plant, William reportedly told garden CEO Poon Hong Yuen, "It's a shame... It's beautiful... Nice, very nice."
William and his wife also had an orchid named after them - the Vanda William Catherine - which is to be planted next to his mother's in the garden's VIP section.