Rose Week is taking place at Sir Thomas and Lady Dixon Park, with a host of competitions and children's activities to mark the occasion.
Thousands of visitors have already turned out to see the park's award-winning gardens.
This year also marks the 50th anniversary of the City of Belfast International Rose Garden.
The garden was established by Belfast City Council, in partnership with the Rose Society of Northern Ireland (RSNI).
On Thursday, judges from New Zealand, the United States and Norway will deliver their verdicts on this year's competing entries for the City of Belfast International Rose Trials.
With points awarded for flowering, fragrance, foliage, disease resistance and length of flowering period, the standard of entries is expected to be very high.
Brian McKinley, from Belfast City Council's parks and leisure services, said visitors return to the event every year because of the number of activities on offer.
"The success of the rose garden and Rose Week is down to the beautiful smell and fragrance that you get from the garden, and the array of colours that you see in the park," he said.
Belfast city councillor Gareth McKee said a plaque would be unveiled on Thursday to celebrate the rose garden's status as a "garden of merit".
"The garden is recognised by the World Federation of Rose Societies as a 'garden of merit' - meaning it is one of the best in the world," he said.
International judges have arrived in Belfast for the city's annual horticultural event this week.