Scientists raise alarm over Table Mountain alien
● In a nursery they look pretty — red bottlebrush flowers tipped with sunshine yellow. But in Table Mountain National Park they are serious trouble, able to spread millions of seeds in a few hours.
Now scientists are recommending the urgent removal of a patch of scarlet bottlebrush plants living on the mountainside near the University of Cape Town (UCT).
If left unchecked the invasive species, introduced to SA as an ornamental plant, could increasingly brush aside fynbos and protea species in the battle for mountain acreage.
What makes the plant particularly problematic is that it releases seeds in the event of fire, tens of thousands of them. If the 1.2ha Devil’s Peak site burns, about 20-million seeds will be released, according to a study in the South African Journal of Botany.
This particular bottlebrush species, part of the Myrtaceae family that hails mostly from Australia, has been seen sporadically in Cape Town since 1961 when it was first recorded in the area around the King’s Blockhouse on Devil’s
Peak. It may have been planted there in a decorative flower bed.
Several years ago it was recorded again in its present location, where 5-10 plants were counted. But by the time researchers surveyed the area two years ago there were 665 plants, a population explosion almost certainly caused by fire.
Now researchers are concerned about what might happen should another wildfire break out, particularly a repeat of last year’s conflagration that narrowly avoided the Melaleuca rugulosa home on its way to destroying parts of UCT.
“Once it gets established in a place like Table Mountain National Park and has all the elements in its favour — like pollinators and fire frequency — it does grow faster than normal fynbos and proteas,” said lead researcher Chelsey Matthys, who is attached to the Cape Peninsula University of Technology and the South African National Biodiversity Institute.
“Within those natural spaces it then starts out-competing the indigenous flora.”
The good news is that it could be worse. Melaleuca is classed as “medium risk” because it takes time to reproduce. It does not grow back as quickly as more invasive aliens such as pines, and the black wattle that chokes many local river systems.
“Some highly invasive plants will come back in about a month after fire but melaleuca will take a year or so to grow back. So it’s all to do with time — with melaleuca we have the time to intervene,” said Matthys.
She and her co-authors recommend immediate clearing to prevent a potential bottlebrush infestation in one of the SA’s global tourist hotspots.
“Prevention is better than cure,” said Matthys. “We should be listing it as high priority and saying let us get rid of it before it becomes a problem. The success rate of clearing it drops the bigger the population grows.”