HORTICULTURE
REBUILDING A
WAR ZONE
WITH THE BATTLE AGAINST A WILE WEED ALMOST WON, THE AUSTRALIAN BOTANIC GARDEN MOUNT ANNAN IS FOCUSED ON REGENERATING A DEGRADED LANDSCAPE. JOHN SIEMON REPORTS.
A
s Foundation & Friends members are well aware, the Australian Botanic Garden Mount Annan has long been at war with a frighteningly formidable foe: the African Olive (Olea europaea ssp. cuspidata). At one stage this aggressive woody weed covered almost 20% of the Garden’s 416 ha landscape. With hindsight, I don’t think any of our predecessors ever anticipated the African Olive would mount such a successful assault. The weed’s growth, while noticeable, seemed of secondary
26 THE GARDENS WINTER 2022
importance to establishing the Garden’s core credentials and, before anyone really appreciated the scale of infestation, it had spread to such an extent that staff were simply unable to tackle the problem by themselves. Peter Cuneo, Manager Seedbank & Restoration Research, completed his PhD in 2012 on ‘The ecology and management of invasive African Olive in southwest Sydney’. In a joint paper, he and Professor Michelle Leishman painted a rather dire picture of the enemy: “individual African Olive trees are
capable of producing more than 25,000 fruits per annum, and able to establish up to 950 seedlings per square metre as a ‘seedling bank’ beneath the crown of mature plants”. Images of Mount Annan, captured by Cuneo across successive decades, highlight just how hostile and transformative this weed is in decimating biodiversity and exterminating all floristic life from the landscape. Through a concerted effort over the last decade, the Garden has now reduced the total coverage of African Olive by a staggering 85%, with less
Photos: Peter Cuneo, John Siemon, © Royal Botanic Gardens and Domain Trust
In autumn 2021 almost 7,500 trees were planted on the slopes of Mount Annan
