A spokesman for Prime Minister Julia Gillard said because the Sultan was visiting Australia as a guest of the government, taxpayers would be meeting at least some of the cost.

''Domestic costs associated with the short visit, including accommodation and land transport, will be met by the Australian government in accordance with usual practice,'' the spokesman said.

''The cost of the visit will not be known until all costs are acquitted.''

The Sultan, worth a reported $20 billion, has been staying at the Hyatt Hotel Canberra and is travelling with an entourage of about 30 people. Ferried around Canberra in a humble Holden Caprice, the Sultan spent day two in the national capital visiting icons old and new: Government House and the National Arboretum Canberra.

He became the 34th head of government to plant a tree at the arboretum but was probably the only one to have his own towel man.

In perhaps a little cross-cultural confusion, as Chief Minister Katy Gallagher watered the newly planted Windmill palm, the monarch also washed his hands under the stream coming from the watering can. A member of his entourage then swiftly stepped forward with a white towel for the Sultan to wipe his hands.

It was probably one of the fastest tree-planting ceremonies in the arboretum's still young history - the royal motorcade in and out within a matter of minutes - but the monarch appeared to enjoy it. ''One more?'' he asked the photographers as he and Ms Gallagher used shovels to toss soil on to the newly planted tree.

The Sultan fitted in a visit to the arboretum as part of his three-day visit to Canberra. ''Thank you for your hospitality. It's a beautiful place,'' the softly spoken ruler said.

Ms Gallagher said the Sultan was the first head of state to plant a tree since the arboretum was officially opened in February but the 34th leader overall.

''The arboretum continues to attract heads of state. They get a choice about where they'd like to come and what they'd like to do when they're in Canberra and increasingly we're seeing they want to leave their mark and plant a tree here in our forest and we're very happy to host them,'' she said

Earlier on Thursday morning, the Sultan was warmly welcomed to Government House by Governor-General Quentin Bryce, who later quizzed him on his travel arrangements to Australia.

''I understand you flew yourself here in your plane,'' she asked the monarch. The Sultan laughed politely. ''That's what everybody talks about,'' the Governor-General told him, with a laugh.

His majesty is licensed to pilot his own plane. It is understood he was behind the controls of the Airbus A340 that landed in Canberra on Wednesday.

Ms Bryce invited the Sultan, one of the world's richest men, to Canberra after visiting his oil-rich nation last year. She and her husband, Michael, greeted him at the front steps of Government House with a friendly ''come on in out of the wind''.

Later inside, she told the monarch she had been anticipating his visit for some time and ''the opportunity to return the hospitality''.

''I had the warmest, happiest memories of my visit to Brunei last year and I'm delighted that you could be here at this time which is significant for your country as you prepare for ASEAN [Association of South-East Asian Nation],'' she told him.

The 66-year-old Sultan said little in front of the media but said he appreciated very much the Governor-General's words. Despite the chilly wind, Canberra turned on a picture-perfect autumn day for the visit, which is being covered by travelling Brunei media.

Lake Burley Griffin was sparkling in the sun, autumn leaves were strewn across the lush green lawns and the cockatoos were squawking in the trees, competing with the national anthems being played.

Smoke hung in the air over the lake as a traditional 21-gun salute was conducted by Australian Defence Force personnel from Weston Park.

The Sultan inspected Australia's Federation Guard and the Royal Military College Band, Duntroon.

The Sultan is due to meet Prime Minister Julia Gillard on Friday.