What Are the Best Plants for Rooftop Gardens?

Rooftop gardens are a great way to make use of the space on your roof and add greenery to urban environments. 

In Australia, the hot sun, strong winds, dry conditions and cold winters can make it difficult for some plants to thrive. 

That's why it's important to choose the best plants for rooftop gardens. By selecting hardy plants that can handle the sun, drought, wind, and cold, you can create a successful and beautiful garden. 

Native Australian plants, succulents, Mediterranean herbs, and ornamental grasses are all great choices. 

These plants are tough, more sustainable with water usage, and perfect for the harsh conditions encountered on rooftops. 

With the right selection, you can transform your rooftop into a vibrant green space that will thrive for years to come.

Best Rooftop Garden Plants for Australian Green Roofs

Rooftop gardens in Australia face unique conditions, including high exposure to sun, wind, drought, and low temperatures. 

Selecting resilient, low-maintenance plants is key. Here are some of the best plants for rooftop gardens in Australia:

1. Native Australian plants
2. Succulents
3. Drought-tolerant Mediterranean plants
4. Ornamental grasses
5. Climbing plants and vines
6. Small trees and shrubs
7. Ground covers

Native Australian Plants

Native plants are well-suited to local environmental conditions and can thrive when chosen correctly. 

Here are some good plants for rooftop gardens from this category:

• Kangaroo Paw (Anigozanthos)

This iconic Australian plant has tubular, velvety flowers shaped like a kangaroo's paw. The flowers come in shades of red, yellow, and green. It prefers full sun exposure and a well-drained substrate. It's drought-tolerant, but it benefits from occasional watering during long dry periods.

• Grevillea

Grevilleas are a diverse group of shrubs or small trees that produce spider-like, nectar-rich flowers. They attract birds, bees, and butterflies. Grevilleas need at least six hours of direct sunlight to grow and thrive. They also need a well-drained substrate. Grevilleas are very drought-tolerant. Once established, they need little to no water.

• Lomandra

Lomandra is an extremely hardy and versatile grass-like clump-forming plant. It's often used for erosion control and ground cover. It thrives in direct sunlight and even partial shade sometimes. It's very drought-tolerant and can grow in various substrate types.

• Banksia

Banksias have distinct, cone-shaped flower heads. They can be grown as shrubs or small trees. The flowers attract birds and wildlife, which is also good for pest control. Banksias need direct sun exposure and a well-drained substrate. They can handle windy and exposed conditions, making them ideal for rooftop gardens.

Succulents

Succulents are some of the best plants for rooftop gardens. They can store water in their leaves and withstand harsh conditions.

Here are some succulents you can plant on your rooftop garden:

• Sedum: 

Sedums are low-growing succulents that come in many shapes, sizes, and colours. They are drought-tolerant succulents, perfect for green roofs. They prefer direct sunlight to light shade and well-drained substrates. They also don't need to be watered often.

• Agave

Agaves are sculptural succulents with large, spiky leaves. They are hardy, architectural plants that thrive in dry, sunny locations. Some species remain compact, making them ideal for containers. They need full sun exposure, minimal water, and a well-drained substrate. They are slow-growing but need little care.

• Aloe

Aloes are succulent plants that produce clusters of tubular flowers in winter. They're low-maintenance and offer vibrant blooms in winter. Aloe vera is a well-known species that has medicinal uses. Plant them where they will receive direct sunlight, but they can also grow in partial shade. They need a well-drained substrate and occasional watering.

Drought-Tolerant Mediterranean Plants

These plants come from Mediterranean climates, which are like many parts of Australia. They're used to dry, hot summers and cool, wet winters.

They're well-suited for sunny, exposed rooftop environments and can make great rooftop garden plants.

Here are some drought-tolerant Mediterranean plants you can add to your green roof:

• Lavender:

Lavender is a fragrant, bushy plant with silvery leaves and purple-blue flowers. It adds fragrance and colour to your rooftop garden while being highly drought-tolerant. Lavender needs to be exposed to direct sunlight, and it should be planted in a well-drained substrate. It's drought-tolerant, but overwatering should be avoided.

• Rosemary

Rosemary is a hardy herb that can double as a culinary plant. This woody herb has needle-like leaves and small, blue flowers. It can be grown as a ground cover or small shrub. Rosemary thrives in the sun, with minimal water once established.

• Oregano and thyme

Oregano and thyme are low-growing herbs that are great for filling spaces. Both are fragrant herbs that can survive in tough conditions. Oregano has oval, green leaves, while thyme has smaller leaves and pink or purple flowers. Both types of herbs need direct sun and a well-drained substrate. They are excellent for culinary and ornamental purposes.

Ornamental Grasses

Ornamental grasses add texture and movement to the garden. They are often wind-resistant and very low maintenance.

Here are some ornamental grass varieties that can make ideal rooftop garden plants:

• Pennisetum (Fountain grass)

This type of grass tolerates heat and adds a soft, flowing texture. It's a clumping grass with arching, feathery plumes that sway in the wind. It has a graceful, flowing look. Pennisetum needs full sun exposure, a well-drained substrate, and minimal water. It's drought-tolerant once established.

• Festuca

Festuca is a low-growing, mound-forming grass with fine blue or green foliage. It tolerates dry and exposed conditions. Festuca provides a soft texture to the garden. It needs full sun exposure to partial shade. You don't need to water it too often, as it can tolerate poor substrate.

Climbing Plants and Vines

Climbing plants and vines can also make good plants for rooftop gardens. They can create shade and soften the hard edges of your rooftop garden.

Here are some varieties to consider:

• Bougainvillea

Bougainvillea is a hardy, fast-growing vine with vibrant pink, red, or purple bracts surrounding small white flowers. It's a sun-loving vine. Bougainvillea thrives in direct sunlight, and it needs a well-drained substrate. Once planted, it needs very little water.

• Jasmine

Jasmine produces fragrant white or yellow flowers. It's often used to climb trellises or walls in rooftop gardens. It's great for both fragrance and creating vertical interest. When young, jasmine needs full sun exposure to partial shade and regular watering. It's a drought-tolerant plant.

• Wisteria

Wisteria is a deciduous vine that produces stunning, hanging clusters of purple or white flowers in spring. It can provide shade and stunning springtime blooms. To control its vigorous growth, it requires full sun exposure, a well-drained substrate, and regular pruning.

• Hardenbergia

Hardenbergia violacea is a climbing plant with branches that twist around the stems of other plants. It is moderately vigorous but rarely covers other plants so extensively as to cause damage. It's known for its shrubby forms without the climbing tendency.

Small Trees and Shrubs

There are many shrubs and small trees for rooftop gardens. They add height and structure to a rooftop garden. 

Make sure to select varieties that are compact and suited to the local condition and that have adequate planting space. These are some options:

• Olive tree

Olive trees are slow-growing and thrive in warm, dry climates. With their drought tolerance and compact size, they're great for rooftop gardens. They produce fruit and have silvery-green leaves. They need direct sun exposure and a well-drained substrate. Once established, they're drought-tolerant and can grow well in pots.

• Lemon Myrtle

Lemon myrtle is a native Australian shrub with fragrant leaves that can be used in cooking. It needs to be exposed to direct sunlight, but it can also do well in partial shade. This shrub needs regular watering when young, but it's fairly drought-tolerant once planted.

• Frangipani

Frangipanis have thick, fleshy branches and produce fragrant, colourful flowers in summer. They are ideal for warm climates. They prefer direct sunlight exposure, and they're drought-tolerant. You can grow them in containers in your rooftop garden.

Ground Covers

Ground covers help provide greenery across larger areas. They are important for filling gaps, preventing substrate erosion, and conserving moisture in rooftop gardens.

Here are some ideas for ground covers for your rooftop garden:

• Dichondra repens

This is a low-growing, trailing plant with small, kidney-shaped leaves. It's often used as a lawn substitute in difficult areas. It's a hardy native ground cover that can handle foot traffic. It needs to be exposed to the sun during the day, but it can also thrive in partial shade. It requires minimal water once established.

• Gazania

Gazanias are low-growing, flowering plants with daisy-like blooms in bright colours like yellow, orange, and red. They make a tough, flowering ground cover that thrives in direct sunlight. They are very drought-tolerant and perfect for hot, dry conditions. They add a burst of colour to your rooftop garden.

How to Choose the Best Plants for Your Rooftop Garden?

When choosing plants for your rooftop garden, you should take several key factors into consideration. Here are the most important ones:

1. Access to the rooftop garden
2. Sun exposure
3. Wind exposure
4. Weight
5. Water requirements 
6. Substrate and drainage
7. Space 

How often will you be able to access your rooftop garden? 

If you're planning to use your rooftop garden for aesthetic and environmental purposes, extensive green roofs may be the best option. They can include plants with lower maintenance requirements. 

But they also grant limited access. If you want to be able to spend time in your rooftop garden, then you should install an intensive green roof.

Intensive green roofs allow for a greater variety of plants, as opposed to extensive green roofs. But this also means more maintenance. 

Rooftops usually receive plenty of direct sunlight, so select plants that thrive in full sun. If your rooftop has shaded areas, consider shade-tolerant plants for those spots.

Rooftops are often exposed to strong winds. Choose plants that are wind-resistant, with sturdy stems and leaves that can withstand windy conditions.

The structural integrity of the rooftop is very important. Make sure that the combined weight of containers, substrate, and plants does not exceed the roof's load-bearing capacity.

Opt for drought-tolerant plants, especially if regular watering is a challenge.

Make sure correct drainage in containers has been installed to prevent waterlogging. Use well-draining, lightweight substrate mixes suitable for rooftop conditions.

Rooftops often have limited space. Consider compact plants, shrubs, or vertical gardening solutions like vines to maximise the available area.

Choosing the Best Rooftop Garden Plants

Creating a rooftop garden in Australia can be a rewarding way to transform unused space into a beautiful, green environment. 

With the right plant choices, you can overcome challenges like harsh sun, wind, and drought. 

By selecting native Australian plants, drought-tolerant succulents, Mediterranean herbs, and hardy grasses, your rooftop garden can thrive with minimal maintenance. 

For expert advice on selecting plants for your rooftop garden, Evergreen Infrastructure provides a team of green roof specialists with extensive knowledge and experience in plant selection.

We're dedicated to transforming urban spaces into lush, sustainable environments. Our green roof consultants can tell you which plants to choose, based on the condition of your roof and many other factors.

If you want to know more about our green roof services, feel free to contact us.

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