Not so Sweet Pittosporum

ITS flowers may be aromatic but there is nothing sweet about Sweet Pittosporum, which is a serious weed tree and is being targeted now in Nature Conservation Margaret River Region’s woody weeds campaign.

The worst weedy trees in the region are in the firing line as part of the two-year campaign, with everyone from suburban gardeners to bush block owners urged to help stop their spread.

Nature Conservation’s Arum Lily Blitz is already a high profile campaign targeting invasive arum lilies, but weedy trees including Sweet Pittosporum, Sydney Golden Wattle, Flinders Range Wattle, Victorian Teatree, Blackwood and even olives pose serious problems by invading bushland and outcompeting native plants.

Sweet Pittosporum is in the spotlight this month because the trees are flowering and setting fruit. They are native to eastern Australia but were planted widely in backyards and gardens across the southwest and now threaten our iconic karri forests. To learn more, there’s a comprehensive Sweet Pittosporum identification and removal video by following the links at www.natureconservation.org.au or to viewed directly HERE.

“At first they take over the understorey but in time they grow into tall trees and shade out the upper storeys as well,” says Nature Conservation’s biodiversity officer Mike Griffiths. “Mature trees can reach up to 12 metres and shade huge areas with their dense crowns. Left unchecked, they degrade our karri forests because they don’t allow new karris to germinate and grow to replace the old trees.”

He continued: “This weedy tree is a lot more widespread across the region than most people realise, including in backyards, roadsides and in bush reserves. It thrives in the forests but does especially well in damp, shady areas like creeklines. We want everyone to recognise it and help stop the spread. They might look attractive and seem harmless, but a single tree can infest the whole neighbourhood as birds carry the seed for several kilometres – all without being noticed by the property’s residents. So it’s important to remove them and replace with locally native species which complement our bushland and benefit the wildlife.”

Sweet Pittosporum has smooth grey bark and glossy green leaves similar to bay leaves, often with wavy margins, and sweet-smelling white flowers. Flowers are followed by orange grape-sized fruit containing sticky seeds that are eaten and dispersed by birds.

“Once you’re confident in identifying the tree, you can hand-pull seedlings or remove larger shrubs and trees with a pruning saw or chainsaw and treat the cut stumps,” says Mike. “Bigger jobs may need qualified contractors or the Nature Conservation on-ground team to bring an infestation under control, but it’s worth it when you think of the threat to the surrounding forests.”

The woody weeds campaign is funded by the WA Government’s State Natural Resource Management Program, and includes funding to be spent on a 50-50 cost sharing basis with landholders located close to high priority bushland, reserves or national parks. To enquire about grant funding, email [email protected] or see www.natureconservation.org.au for more information.