NESTLED amid native bushland as surely as Versailles was carved out of French forest, the Australian Garden at the Royal Botanic Gardens Cranbourne is a highly stylised intervention. Landscape architects Taylor Cullity Lethlean and plant designer Paul Thompson make no pretence of giving us the naturalistic or the wild.

Like their first stage of the garden (which opened in 2006), this second and final instalment is a formal, carefully resolved space that - with much artistic licence - interprets the diverse land types and plantings of Australia.

We get lakes, estuaries and the seaside. We sample forests and tree-lined avenues. We peruse the suburban backyard. But - and this is the really clever thing - such theme-park juxtapositions don't come at the expense of unity.

Visitors will wander from the Melaleuca Spits up to the Weird and Wonderful Garden and through Casuarina Grove and cross no definitive dividing lines. Arid rock outcrops seamlessly descend into inland rainforest and coastal estuary. Such merging is largely through the ever-shifting textures and paving types: crushed shell gives way to super-smooth concrete, to gravel, to stone, mulch, steel-grill and (my personal favourite) pock-marked concrete.

This last - weathered and covetable - is central to the Gondwana Garden, which also gets one of the new shelters designed by BKK Architects. This multi-purpose space has a roof like a leaf and airy walls composed from poles of timber and steel. It's less angular and minimalist than some of the other new shelters but, like all of them, it is assiduously unobtrusive and blends the indoors with the out.

The indoor element is critical when the plants themselves cast little shade. For while there are plenty of trees that will ultimately lend height, few do so yet. It's one thing to talk about the gardens now, only three weeks after they opened, but the really interesting thing will be to see how the mood shifts, and some of the hard edges soften, as the plants (even the highly manipulated ones, and there are many of those) grow.

At this point, however, the gardens are still largely dominated by the hard architectural elements. And how can a young plant compete with vast walls of rammed earth, expanses of Corten steel and towering shards of Castlemaine stone?

The Arbour Garden, for example, has a long line-up of wire-grid walls, all the better for showcasing the vigour of Australian climbers. Ultimately we can expect a series of green walls with a verdant tunnel for a pathway. But right now only the kennedias have really taken and there is more grid to be seen than green.

Similarly the formal avenues of Hill's weeping figs (Ficus microcarpa var. hillii) are not yet lush and luxuriant in that Queensland forest way so that the chairs below them (Tuileries-style) aren't as inviting as they might be when the trees fill out.

There is a playfulness to the Australian Garden though that doesn't rely on the plants alone. Water forms puddles in dips in the gravel and - in the rain - cascades over a rocky outcrop into a lake below. Paths wriggle in crazy hairpin turns, a bridge takes the form of lily pads and pairs of thongs adorn the seaside area.

Like many of the spaces here the seaside garden does not differentiate between path and plant bed. For a central tenet of these gardens is that you get right up close to the plants and experience them in new ways. There is extensive labelling and a multitude of information panels, all the better for trying it out at home. But the theatre and ambition of the space mean the gardens will also appeal to those not intending to toil their own soil.

For while the new areas might not yet be verdant enough for lolling and lazing, they make the perfect outdoor art installation. There is also plenty on offer for the active, curious child. My own teenagers opted for the nearby indoor skate park instead.