Design of the Australian Rock Garden

Design of the Australian Rock Garden

I wrote recently about the Australian Rock Garden at the Arboretum & Botanic Garden at UC Santa Cruz, as a resource for home gardeners. For today’s column, we’ll outline the history, design and development of this special feature at the Arboretum.

The accompanying photographs have been provided by the Arboretum’s volunteer photographer Bill Bishoff, with our appreciation.

In the mid-1980s, the Arboretum received a large shipment of topsoil (some 15,000 cubic yards) that had been excavated from another location on the UCSC campus. This soil was delivered to the Arboretum’s Australian Section, designated as the Elvenia J. Slosson Research Garden.

The Australian Garden’s Curator, Melinda Kralj, had conceived the development of a mounded rock garden in two sections, representing southwestern and southeastern botanical regions of the continent “down under.”

These regions are compatible with the world’s Mediterranean climate zones (also called summer-dry regions), all of which are represented at the UCSC Arboretum.

Australia’s diverse geography includes a wide variety of landscapes, in addition to these summer-dry regions. They include tropical rainforests in the northeast, mountain ranges in the southeast, southwest and east, and desert in the center, commonly known as the outback.

The space between the Australian Rock Garden’s western and eastern mounds serves as a visitor’s pathway linking the two planted mounds, and symbolizes Australia’s large desert or semi-arid area between the coasts,

The design concept envisioned the western region’s mound would display native Australian plants extending the western beach to an inland area, and the eastern region’s mound would feature plants from an inland area to the eastern coast. The plants on each mound also would be positioned to align with their coastal or inland natural habitats.

This design concept reflects the Arboretum’s focus on botanical research and education and provides visitors with a living demonstration of a target area of this continent’s botanical diversity. To dig deeper into this topic, browse to and search for “Flora of Australia.”

Curator Kralj had both the vision and the lead role in the development of the Australian Rock Garden as heavy equipment shaped the huge mounds of soil and many tons of boulders. These boulders were selected from area suppliers to be consistent with Australian geology. (Other areas of the Arboretum include limestone boulders found on the UCSC campus.) This work continued from 2008 to 2016, as gift funds supported the project’s progress.

As with all gardens, the Australian Rock Garden continues to evolve as the original plants mature and new plants are acquired to refine the design of the installation. The early installation of a solar-powered pond feature did not succeed, so an aquatic feature might still be added, dependent upon electrical service to the Rock Garden.

Early in Melinda Kralj’s Arboretum career at the Arboretum, she gained deep knowledge of Australian plants from extended research visits to the continent with founding director Ray Collett and other Arboretum staff and studied with Australian plantspeople.

She retired from the Arboretum staff in June of 2021. Brett Hall’s review of Melinda’s productive work at the Arboretum can be found online at She still contributes her time and expertise in the Australian Rock Garden, which will also be known as her inspired creation.

This Garden’s popularity as a feature of the UCSC Arboretum began with its earliest existence and continues to evolve as a resource for visiting gardeners.

Tom Karwin is past president of Friends of the UC Santa Cruz Arboretum and the Monterey Bay Iris Society, a Lifetime Member of the Monterey Bay Area Cactus & Succulent Society, and a UC Master Gardener. He is now a board member of the Santa Cruz Hostel Society, and active with the Pacific Horticultural Society.