The Kings Park Special Callistemon has been an international success story. This one (photo by wiki commons user Melburnian under Creative Commons) is flourishing in Maranoa Gardens in Victoria.

THE first generation of Kings Park Special bottlebrushes are dying off.

A cultivated variety of Callistemon developed through breeding, the KPS was an early success story in plant development for Kings Park and Botanic Garden. 

The original seedling was of “unknown origin”, cultivated into its current form by the park’s first nurseryman Ernst Wittwer, a Swiss horticulturalist who’d trained at Kew Gardens.

The species was registered in 1980, and in the following decade countless KPS Callistemons were planted across Perth’s verges and have since become popular in cities around Australia for their bright colours and attracting birds and insects. 

But it appears the first cohort are growing too old to withstand water stress and heat.

In 2019 and 2020 KPS Callistemons made up the vast bulk of trees that died on Vincent council’s verges. 

They’re known to be sensitive to drops in the water table, while an arboricultural assessment couldn’t find any specific disease or bug affecting them (“Mystery ailment knocks off trees,” Voice, November 16, 2019). 

This summer the KPS also made up the majority of trees dying off in Bayswater, with a report showing 53 of the 134 dead verge trees were Callistemons. They only make up 10 per cent of Bayswater’s verge trees, but are overrepresented with 40 per cent of this summer’s casualties.

Bayswater’s parks and gardens staff write in the report there’s various possible causes like heat, disturbance from development, and water stress. Trees are more susceptible to these factors when newly planted or when they grow too old to tolerate harsher conditions. 

“Callistemon Kings Park Special rarely lives beyond 40 years of age,” the report says.

Vincent has phased out planting KPS Callistemons, mostly replacing the dead ones with melaleucas. Bayswater’s also removed them from its current tree planting guidelines in favour of species like some of the shorter eucalyptus species and some exotics like Swan Hill olives, crepe myrtles and Chinese pistachio trees. 

by DAVID BELL