For three decades, National Tree Day has brought neighbours together, introduced children to the natural world and given millions of Australians a simple, tangible way to care for the places they live.

While environmental challenges have grown more complex over those 30 years, Costa believes the enduring appeal of National Tree Day lies in its simplicity.

"I think above all else Tree Day is such an inclusive event, anyone and everyone can be involved," he says.

"People can actually really walk away knowing that they've actually been activists. They've said yes there are problems moving forward, but rather than just talking about it, let's do something."

For Costa, that "something" is a powerful act that creates a lasting connection between people and place, bringing ourselves closer to where we belong.

"Planting a tree has such enormous consequences. I love the idea that people can plant it in their neighbourhood and watch it grow and feel like they are genuinely a part of the change. And the solutions."

Costa as the Gnome helping children plant for National Tree Day 2017.

That idea of watching change unfold over time is one of the reasons he believes National Tree Day has endured for 30 years. In a world that often feels increasingly fast-moving and disconnected, National Tree Day offers something reassuringly familiar. Every year communities return to the same parks, creek lines, schools and reserves, not simply to plant more trees, but to see how the trees planted years earlier have grown.

"They get to observe and appreciate the efforts of those before them, including themselves. People really need to see the follow up, the results of taking action. And National Tree Day makes that possible."

For Costa, this continuity creates something powerful. It reminds people that environmental restoration isn't built on grand gestures, but on thousands of small actions repeated year after year.

Costa with volunteers at a National Tree Day planting in 2010.

Those little actions taken on National Tree Day also offer a time for reconnection with nature, something that has become increasingly relevant as our lives move further indoors and onto screens.

"National Tree Day gives everyone not just the invitation, but the opportunity to be present in nature. The reality for all of us is that we are nature,” he says.

“We come from nature. We need nature. We are nature."

"When we connect the heart to nature, then we suddenly reprioritize and realise that the beauties around us, we live in nature. Nature's our true home."

Perhaps nowhere is that connection more obvious than when children attend their first National Tree Day. Costa has watched countless young Australians pick up a trowel for the first time, get their hands dirty and discover a world many adults have drifted away from.

Young planters like this one in 2013 always have a good time when Costa is around.

Families who may never have thought of themselves as "outdoors people" suddenly find themselves kneeling in the soil, discovering native plants, following waterways through their local landscape and seeing their neighbourhood, or ‘naturehood’ as Costa would prefer, with fresh eyes.

For children, Costa believes these experiences can shape the way they see the world for the rest of their lives.

"I think the real impact that it has is that it shows them that they're part of the world. They're a small part of this big, wide, amazing world and they can give back to it."

"National Tree Day's about giving back to nature. It's saying, hey, we want to regenerate. We want to help rewild. We want to help rebuild."

Not just a gardener, but a speaker, educator and all around great human being!

Looking ahead to the next 30 years, Costa isn't thinking about a single planting day each July. He's imagining connected landscapes where the trees planted by communities today link schools to parks, creek lines to backyards and neighbourhoods to thriving ecosystems.

"I'd like to time travel to 2056 and say, wow, look at what these collective efforts achieved in protecting our waterways, in building urban biodiversity, in connecting communities."

For him, that is the true legacy of National Tree Day ready to be realised.