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According to research published in August in PLOS One, cloud cover will increase and rainfall will decrease in the future. This will make it harder for jacarandas in cities like Perth to flower.
The jacaranda – native to arid parts of the Andes in Argentina and Bolivia – needs to be exposed to the cold to flower.
Jacarandas are blooming later this year.Credit:Louise Kennerley
The citizen science project found large variations across Australia in the length of the flowering season, which was shortest in Melbourne; peak flowering time, which is usually October in Sydney; and the length of the season, longest in Perth.
In areas like Melbourne, warmer summers could aid jacaranda growth and development, but in Perth, warmer winters may prevent flowering.
Barrett, who was not part of the citizen science project, said the changes were unlikely to affect Sydney’s jacarandas.
In South Africa, scientists have tracked the changes in jacaranda blooming times by reviewing newspaper reports of sightings.
Jacarandas in bloom in McDougall Street, Kirribilli, in October 2017.Credit:Nick Moir
Writing in The Conversation, Jennifer Fitchett, associate professor of physical geography at the University of the Witwatersrand in South Africa, said the trees in Johannesburg and Pretoria had started to bloom in mid-November in the 1920s and 1930s.
“The date of bloom has advanced through October to the early weeks of September,” she wrote.
This is a phenological shift, a change in the timing of annually recurrent biological events because of climate change.
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Her paper says: “If plants flower too early in the year, they are at risk of frost damage during the late winter months, and often do not complete their dormancy. These advances in flowering dates cannot continue indefinitely. At a critical threshold, the flowering season will become unsuccessful.”
In bloom
Jacarandas aren’t blooming just yet but there are other plants in fine form at the moment:
Puyas (Puya alpestrisin) in The Beach garden area of the Blue Mountains Botanic Garden, Mount Tomah. Known as sapphire towers, the plant has spikes up to two metres tall. Each plant can take up to seven years to flower.
Puya flower Puya alpestris in Blue Mountains Botanic Garden Mount Tomah.Credit:Royal Botanic Gardens and Domain Trust
Native hibiscus (Alyogyne) a deep purple shrub, in the Connections Garden at Australian Botanic Garden, Mount Annan.
Weeping boerboon (Schotia brachypetala), a flowering tree from Africa, near the Sydney Fernery at Royal Botanic Garden Sydney.
A weeping boerboon at Sydney’s Botanic Garden.Credit:Royal Botanic Gardens and Domain Trust