A garden like this on a city rooftop? That’s ingenious

Some landscape projects are truly exceptional. Like this 450sqm roof terrace - price tag, half a mill - on a Melbourne penthouse.

Wow factor: the roof garden in St Kilda Rd, Melbourne. Picture: Erik Holt

Some landscape projects are truly exceptional. For this 450 sqm roof terrace surrounding a penthouse on Melbourne’s St Kilda Rd, the exacting design brief, engineering requirements and physical challenges meant a budget exceeding $500,000 – but the results are spectacular. The project by Lisa Ellis Gardens, which used virtual reality technology to fine-tune the design, won two gold medals in the 2021 awards of the Australian Institute of Landscape Designers and Managers.

The terrace gardens are both a transition and a counterpoint for the bespoke internal build, as every room is positioned around the views to mountains, city skyline, parks and the bay. The garden design and plant selection had to enhance these views but also provide selective screening from neighbouring buildings.

Lush garden beds. Picture: Erik Holt

The owners, a professional couple, wanted more than just beauty for their “home in the sky with a garden” – they asked for discovery, surprise and whimsy to enhance moods and trigger emotional delight. Ellis’s response was to create a series of distinctive outdoor rooms, encompassing outdoor dining, a 9m-wide “infinity lawn”, cloud-clipped shrubs, a productive garden, swaying grasses and rustling bamboo.

She designed the bespoke sculptural elements – an undulating rod fence that appears to be falling over, which acts as a spine through tall foliage, and a light-rod garden set among a haze of mauve Russian sage (Salvia yangii) blooms. The vertical rods of various heights emulate the city skyline; at night their lights, each programmed with dimmers, heighten the effect.

The “infinity lawn” was raised to the base of the oversize windows because “when the client was on his running machine he wanted to look out over green lawn to the Dandenongs”, Ellis explains. The lawn is framed by clipped shrubs that make it feel embedded within a traditional garden space.

Looking out over the city. Picture: Erik Holt

To finesse the design, Ellis’s team utilised virtual reality simulations at the concept stage. “VR offers an unparalleled design tool to double check the detail of every element,” she says. “When you put on the headsets in our VR room you can walk through the entire garden at 1:1 scale.”

Resolving the engineering to distribute loads across the slab was Ellis’s biggest challenge. “Whenever you’re designing for rooftops, loading will drive what is possible,” she says. “Most roofs are engineered to take 200kg per square metre. Factor in pavers, wet soil and plants and there’s not much left – if you want to bring in heavier elements you have to calculate bracing to redistribute that load.”

Each of the garden beds comprises a drainage cell, geotextile and a specialised soil mix on top of the concrete shell. The plants were scrupulously selected to perform in the exposed, windy conditions and shallow soil depths, as well as to offer textural contrast and appeal.

The clients are so thrilled with the result that they’ve engaged Ellis for their next project.

Q&A

What are some easy-care indoor plants that are safe for my cats? Pam McMullen, Doonan, Qld

Poisonous2Pets by Nicole O’Kane is a great reference. All liliums (including cut flowers) are extremely toxic to cats. Peace lilies (Spathiphyllum) are in a different family but are moderately toxic to cats and dogs, as are anthuriums, begonias, monsteras, caladiums, syngoniums, cyclamen, ivy, ZZ plant (Zamioculcas), philodendrons, Epipremnum, Dieffenbachia and umbrella tree – but animals rarely eat serious quantities. High-toxicity plants include dracaenas and kalanchoes. Safe plants include African violets, Boston ferns, palms, orchids, mistletoe cactus (Rhipsalis), Maranta, Calathea, Peperomia, Cissus, Aspidistra, Chlorophytum, Dizygotheca and Hoya. If you have a sunny or bright spot, grow a pot of catgrass (Dactylis glomerata) – cats love to eat it and it’s good for them.

My beautiful camellia is all bud and no bloom this year. Buds that do start to open wither and drop before maturity. Is the heavy, prolonged rain a factor? Karen Williams, Brisbane

Constantly wet soil could cause bud (and leaf) drop, as can dry soil. Wet petals of opening buds can get sunscald or even a fungal infection, preventing opening. Simply having too many buds can cause some to be shed; thinning them early helps channel energy to the remainder.

What winter vegetables could I grow in a small area with raised beds? Sue Stanlake, Cowaramup, WA

Try broccoli, kale, English spinach, leeks, spring onions, Asian greens and snow peas.

Wallgarden modules

Send your questions to: [e-mail] or Helen Young, PO Box 3098, Willoughby North, NSW 2068. Website: helenyoung.com.au. The best question for May wins two boxes of 10 Wallgarden modules giving 2 sqm of planting space, worth $190. wallgarden.com.au