Australia Weather News

The National Arboretum, which has been slowly taking root in Canberra for almost a decade, has seen its forests explode in growth after a deluge of rain this summer.

After spending the past eight years focused on just keeping its 100 forests alive through drought, heat and bushfire smoke, the arboretum's managers say the site has received a year's worth of rain in just six months.

The rain brought on the greatest growth in the arboretum's history — more than 30 per cent growth in many of its forests, according to manager Scott Saddler.

"[Compared to] the last seven years or eight years the trees have been in, this year has been extraordinary," Mr Saddler said.

"You can see the line of growth a foot or two above the tree."

But Mr Saddler said it was underground where the rain was making itself felt most.

"What [the rainfall] means for the trees is that the root systems are able to get down deeper, and it makes the trees more resilient," he said.

"So this particular rain has been just a godsend."

He said it had even been enough to "future-proof" the trees against future droughts and other hardships.

Irrigation system feeds water directly to 44,000 trees

The National Arboretum has been open for almost a decade, after years of painstaking work to slowly cultivate dozens of native and introduced forests over land that was razed in the 2003 Canberra bushfires.

But some of its forests struggled in its early years.

In 2016, just three years after its opening, a review found as many as 10 per cent of the trees had died, and many more were dying.

One reason for the high failure rate was due to the experimental nature of attempting to grow forests of foreign species.

The arboretum has since spent millions installing irrigation systems, including the ability to pump as much as 200 megalitres of water from Lake Burley Griffin.

"We have a water strategy project that delivers water to every single one of the 44,400 trees," Mr Saddler said.

"They're all looked after — they've all got their own drip tubes which send six litres of water to the trees per hour."

Mr Saddler said now that the trees had taken deeper root, the arboretum's irrigation system all but guaranteed the forests' survival.

In fact, though it is many years off, Mr Saddler said some forests would ultimately have to be "thinned" to ensure their continued health.

"Potentially you could dig those trees out, and utilise arboretum trees across Canberra — they won't be just destroyed, we will have plans in place, for developers and for government ... to be able to utilise these trees in a whole range of areas," he said.

"Imagine having an arboretum tree in your backyard. Or driving down the street seeing a street lined with arboretum trees."