They planted a West Australian flowering gum at the Winmalee Guide Hall as they visited the town in Yellow Rock, north-west of Sydney.
A plaque underneath (pictured) read, ‘Planted by their Royal Highnesses the Duke and Duchess of Cambridge, April 17 2014.’
The royal couple also met firefighters and State Emergency Service volunteers and NSW cabinet minister Mike Gallacher.
William, Kate and baby Prince George arrived in Australia on Wednesday, having completed a tour of New Zealand.
Image via Getty