Jacaranda trees adapt to the effects of climate change
In time, the beloved trees will be unable to cope with ever-earlier flowering seasons.
Did you know?
- Gauteng’s Jacaranda trees originally came from Brazil
- Jacaranda trees were introduced to South Africa in the early 1800s
- The first trees were planted in Pretoria
- Jacaranda trees are invasive and replanting them is prohibited
- About 16% of the land in Gauteng’s city regions are planted with trees, forming one of the world’s largest and most densely vegetated man-made urban forests
- It is estimated that Johannesburg alone has 10-million tree
- In the 20s and 30s, Jacaranda blooms only began in mid-NovemberJacaranda trees can live to 100, with many of the original trees exceeding their centenary.
Information compiled from Dr. Jennifer Fitchett, Wits University.
********
Sydney Richfield wrote a poem 1929, dedicated to Pretoria.
Richfield, a composer, was born in London in 1882 and came to South Africa in 1920. He settled in Pretoria in 1928, where he died on 12 Apr 1967.
Source: Anton van Vollenhoven, North-West University.
In Jacaranda Time
Jacaranda Blue,
Fresh with morning dew.
Ev’ry eye alluring
With its grave enduring.
To a fairy call,
Petals softly fall.
For the idler treading
A magic carpet spreading.
Azure blossoms ev’rywhere
Resplendent in their beauty,
Balmy Spring is in the air.
Filling nature’s duty.
Birds are singing in the trees,
Happy in their freedom.
Fragrance is in ev’ry breeze,
In Jacaranda time.
************
Gauteng is currently draped in a purple haze as Jacaranda trees bloom, a time much looked forward to by residents and enjoyed by tourists.
Wits Associate Professor of Physical Geography Dr Jennifer Fitchett has studied the flowering times of the much-loved trees and the impact of climate change on them.
“In 2019 I noticed the trees began blooming in mid-September on campus, a full month and a half earlier than normal,” she said.
She explained how seasonal changes (temperature changes) can trigger phenological events in plants, or the timing of flowering in spring, fruit development through summer and leaf colouration and fall in autumn.
“As the world’s climate warms, events in the plant and animal world triggered by spring are now occurring in winter, and early summer being experienced in mid-spring.”
Over the period 1918–2019, June average maximum daily temperatures have increased by 0.2°C a decade, while average minimum daily temperatures have increased by 0.2–0.5°C.
Her research shows how there has been a 2.6-day advance in flowering of the trees from 1919 to 2019. “This explains the trees’ ability to adapt to increasing temperatures, but the advance of flowering cannot occur indefinitely as it will progressively affect the trees’ capacity to absorb water, cycle nutrients and withstand stressors.”
This coupled with restrictions on replanting the alien trees means our purple forest will in time be threatened, especially as the trees on average only live for 100 years.
This phenomenon is also noted with Japanese cherry blossoms. “Not only are cherry blossoms a key tourist attraction, and the cherry festivals important cultural events, their study is also the world’s longest phenological record. Phenological analyses show that current cherry blossoming is occurring earlier than any time in the last 1 200 years.”
Related Article:
Delta Park school plants vegetable beds and fruit trees for children
