Royal photographer Tim Rooke has opened up about taking photos of the famous family and revealed a quirky tidbit: Prince Charles shares a message with the trees at every royal planting.

Rooke, the Royal Photographer for Rex by Shutterstock, discussed how he’s had the opportunity to photograph Prince Charles at tree-plantings during an interview with Vanity Fair.

He acknowledged that even though the Prince of Wales’s new members of staff don’t expect it at first, Prince Charles has a certain ritual when it comes to putting a tree in the ground.

“The Prince of Wales has quite the way of planting trees,” Rooke said. “Every time he gets a new member of staff, we tell them what he’s going to do, and they say ‘oh no, he won’t do that.’”

However, according to Rooke, after Prince Charles has planted a tree, he says: “Good luck, tree.”

The prince has been quite involved in the Queen’s Green Canopy, which had encouraged people to “plant a tree” in honour of the Queen’s Jubilee celebration that took place earlier this month.

In May, he unveiled 70 ancient woodlands and 70 ancient trees dedicated to the Queen.

Rooke also told Vanity Fair that, aside from photographing Prince Charles’ involvement at tree-plantings, he captured the royal while he was holding his grandson, Prince Louis, in his lap.

“I thought that was nice, because he’s just a granddad, isn’t he?,” he said. “You sort of forget that these people are just normal…Well, they’re not normal people obviously. But they’re people, with their grandchildren and their great-grandchildren.”

Regarding how he works with the royal family, he noted that he and the other photographers have a “symbiotic” relationship with them.

Rooke also addressed the importance of “getting the job done,” as the goal is to get “good pictures” for promotional purposes, which he said that the family understands.

“We need to take pictures, and if we take good pictures—if they allow us to take good pictures—of their charity work, those pictures will get used in the newspapers and magazines, and that promotes the charity,” he continued. “If they were all grumpy all the time, then it wouldn’t really work. I think there’s an understanding that we all have a job to do.”

Although he acknowledged that his job can be challenging, Rooke still expressed how he was happy with where his career has gone, as he took a different path than his grandfather, who was a miner based in Canada.

“The monarchy will hopefully carry on, and not just for selfish reasons,” he joked. “Yeah. I probably got 15 [working] years left, so I’m sure it will last longer than that.”