Dunedin Botanic Garden collections supervisor Dylan Norfield said some of the garden's magnolias, camellias, rhododendrons and snowdrops had started flowering in the past week.
The magnolias in question would normally flower at the end of August, and the snowdrops usually flowered in early September, he said.
''It's not across the board. Not all are flowering. Just the odd one.''
Climate was the main reason for plants flowering early.
If soil and air temperatures were above average for an extended period, leaf and flower buds might sprout ahead of schedule, he said.
''It's one of the driest couple of months that we've known at the gardens here. Some areas were starting to wilt until we had the rain at the weekend.
If the weather continued to be warm and dry, deciduous trees like maples could start to bud as well, which was of concern, he said.
Cold weather could still arrive in the next few months, which would not be good for plants that had already started flowering.
''It could be an issue. We're still likely to get some of those late frosts, and if they come out [bud] too early, it will kill those buds that come out and they will have to use up their auxiliary buds and it will make the plants a bit weaker.
A MetService spokesman said Dunedin's average mean temperature for July was 4.9degC.
However, so far this month, the average mean temperature has been 5.9degC.
