The gardens come back to life this November due to a month of “unusually warm” weather.
Flowers and plants are entering a “second spring” due to warmer conditions, prolonging their bloom for months longer than usual, horticulturists said.
Their change in behavior could have an impact next spring as well.
This month in the UK was 2.2C warmer than the average November, according to the Met Office.
Nikki Barker, senior consultant at the Royal Horticultural Society, said the mild weather had created some unseasonable views in the RHS public gardens.
“Things we would expect to flower in October, like fuchsias and salvias, are still flowering now and showing no signs of stopping,” Ms Barker said.
“The roses are putting on new buds and still producing, so it’s a pretty big extension of the flowering season.
“I still have cilantro growing in my garden.”
Pippa Greenwood, a botanist and manager of the Horticultural Trades Association, said the way our greenery is responding to the balmy weather is “completely crazy and mixed.”
“If you look out the window, you’ll see a strange mix of some trees that are a little drought-stressed and have leaves, while some have lost their leaves weeks ago,” he told BBC News.
“Some stick to the calendar, while others are blooming for the first time this year.”
The mild November weather is the latest in a chain of weather events that impacted the life cycle of our gardens this year, disrupting the time when we’d normally expect our summer blooms to wilt.
“During the drought this summer, many plants went dormant like in the winter, but they were doing it in the summer because it was too hot,” Barker said.
“We’ve had a lot of rain this month, and it’s been very mild, so it’s been producing a lot of new growth.”
While horticulturists have welcomed the opportunity to enjoy our gardens for a little while longer, they warn that the turn of events could have a negative effect well into next spring.
“Some plants are using up a lot of resources now, so they could be flowering late next year,” Ms Barker said.
“If things go out of place when they flower, things that feed on them like insects are knocked out of place and blue tits feed on insects early in the year. It has the potential to disrupt many life cycles.
“Extreme weather events are becoming more common. We may not know the effects for several years.”
The Met Office said while November still has some time to run, the month was “significantly milder” than the average for the past 30 years.
However, the spell of sunny weather looks set to end soon, bringing UK gardens back into sync.
“High pressure will move in from the west from the middle of next week which will stabilize the weather,” National Weather Service spokesman Stephen Dixon told BBC News.
“There will be calmer weather, less rain in the southeast and temperatures will be brought back to average.”
Climate change can increase the frequency and intensity of extreme weather events, such as floods and extreme heat in the UK.