MELBOURNE, Australia (AFP) — Novak Djokovic has long credited a series of unusual methods for helping him become one of the greatest players ever, not least his 15-year "special relationship" with a Melbourne tree.

The world No. 1, who swears by a plant-based diet, extols the virtues of meditation and has previously used a spiritual guru, has never been shy of talking about his eccentricities.

As he targets an unprecedented 11th Australian Open title, he said he had been connecting again with his "old friend" — a Melbourne fig tree in the city's Royal Botanic Gardens that he likes to hug and climb.

"It is true. It is true. There's one particular tree that I've been having a special relationship with, so to say, in the last 15 years," he said after battling into the third round on Wednesday evening.

"I love every corner of the Botanic Gardens. I think it's an incredible treasure for Melbourne to have such a park and nature in the middle of the city.

"That particular tree, I cannot reveal which one, I'll try to keep it discreet for myself when I'm there to have my own time. I like to ground myself and connect with that old friend."

Djokovic broke through for his first Grand Slam title at the 2008 Australian Open and he has been a regular visitor to Melbourne since, long professing an affinity with its vegetation.

Asked why he was attracted to that particular tree, he replied: I just liked it.

"I liked its roots and the trunks and branches and everything. So, I started climbing it years ago. That's it. I just have a connection."

Earlier in the tournament, he insisted he was not superstitious "but I do obviously like to visit certain places that have brought me luck."

"Just be by myself in nature, just grounding, hugging trees, climbing trees and stuff," he said.

"Whether that's the secret of success here in Australia or not, I don't know, but it has definitely made me feel good."

The Serbian's fondness for the unusual has made him stand out from his peers, who enjoy a more straightforward lifestyle.