You’ve decided to get a green roof, but now you need to add the green to your roof and pick out some plants. What are the best plants for a green roof? Succulents or grasses, shrubs or wildflowers?
Plants provide many benefits: They lower the urban heat island effect, decrease anxiety, manage rainwater runoff, and provide cleaner air.
You want to be sure the plants you select will be able to survive your local climate. If you’re looking for a guide to get started, here is a list of some of the best plants to get for a green roof.
What is a Green Roof?
Green roofs go by many names: rooftop gardens, eco-roofs, and living roofs. Some might think a green roof means that a roof is eco-friendly, but the name is a bit more literal. A green roof is a vegetative layer grown over a growing media and a waterproof membrane. There are several roofing layers:
- Structural roof decking
- Vapor barrier
- Thermal insulation
- Root barrier
- Drainage layer
- Filter membrane
- Growing medium
- Vegetation layer
Living roofs find their origins in 1960s Germany. Since then, they have gained popularity and the roofing style has spread to other parts of the world.
Green roofs are expensive and the heaviness of the soil and plants puts structural stress on a building. They are designed for flat roofs with no more than a 45-degree slope.
There are three types of green roofs:
- Intensive roofs are as the name suggests, intensive. The deeper soil supports a wide variety of plant life, even trees. They weigh about 80 to 150 pounds per square foot and can be anywhere from 10 to 36 inches deep, or even deeper in some cases.
- Extensive roofs are not as heavy nor as deep as intensive roofs, usually only about 6 inches deep. They support a limited number of shallow-rooted plants.
- Semi-intensive roofs are a combination of intensive and extensive roofs.
Depending on the type of green roof, they support many kinds of plants:
- Bushes
- Flowers
- Grasses
- Mosses
- Shrubs
- Trees
The benefits of green roofs include: eco-friendliness, stormwater management, cooler temperatures, waste reduction, and cleaner air quality.
What Makes a Plant Good for a Green Roof?
When considering what plants to get, there are several factors to consider:
- Aesthetic. Homeowners will want attractive plants to match the colors and aesthetic of their home.
- Climate. Geographic climate affects the types of plants you can have on your roof. Hot, arid climates will not suit certain plants. Other plants won’t be able to withstand colder northern temperatures. Native plants are generally a good option. USDA hardiness zones help determine which areas are good for certain plants within geographic zones. Hardiness zones are a good way to check if your plants are suited to the local climate in your area.
- Roof type. Extensive green roofs greatly limit the types of plants that will fit on your roof. Intensive roofs offer a much broader selection.
- Size. The size of your roof will depend on how many plants you can fit on your roof and how big they can be.
You wouldn’t want to plant a roof garden only to have it succumb to bad weather. Green plants should be hardy, tough, drought-resistant, frost-resistant, and low maintenance. They must withstand the local climate and be able to survive in poor soil.
The raised height of roofs leaves plants exposed to the elements, making roofs a harsh spot for plants to live in. Not just any kind of plant can thrive on a roof. But what type of green roof plants should you start with?
Grasses
With root systems that are neither long nor extensive, grasses can grow in shallow substrates. Grasses fill in areas and add lushness to your roof’s vegetative layer.
Not every type of grass can survive on a green roof, but there are several varieties of ornamental grasses that are suitable for a green roof.
Herbs
Herbs offer many benefits apart from being beautiful vegetation. Some are edible or offer medicinal benefits. Typically, they are pleasant-smelling.
Herbs are often shallow-rooted plants, making them a great choice for green roofs.
Shrubs
Shrubs aren’t an option for every green roof, since they are only feasible on intensive or semi-intensive green roofs. Shrubs require a substrate with a depth of at least 10-20 inches.
Before planting shrubs, you will need to consider how much weight your roof can handle. Large shrubs can weigh 35 to 80 pounds, so it will take a sturdy roof to support them.
For homeowners looking to increase biodiversity, shrubs create shelter and safe places for wildlife.
Succulents
Succulents are tough plants and the most popular choice for green roofs. For those who want a colorful roof, succulents come in many different colors.
Hardy and drought tolerant, succulents don’t require much water to flourish and can survive in shallow soil. Certain types can even grow in rocks or bricks.
Succulents don’t require a lot of water and can handle extreme temperatures. They store up water, allowing them to survive dry spells. If they are exposed to extended heavy rains, the wet conditions can cause their roots to rot.
The most common type of succulents are sedums. There are over 400 sedum species. Sedums, also known as stonecrop, are hardy plants that have several benefits: shallow root systems, disease resistance, and drought tolerance.
Trees
Only intensive roofs with a deep substrate and a lot of structural support can handle a tree on top of the roof.
Trees must be fairly small, with a maximum height of 16 feet. For a plant of this size, the soil depth must be more than 40 inches deep.
Trees are high-maintenance plants, so they will have to be regularly watered, pruned, and trimmed, just like any other tree.
Wildflowers
Looking to add a splash of color to your sea of green? Everyone loves the colorful beauty of flowers. They aren’t just an attractive choice for people to enjoy – helpful pollinators such as butterflies and bees enjoy them, too.
Wildflowers generally have shallow root systems that make them perfect for adding flamboyant color to your green roof.
Best Plants for Extensive Roofs
Extensive living roofs generally only have a growing substrate layer of 6 inches. Because of the lack of depth, it limits the types of plants that can grow on your roof.
But not to fear. If you are planning on getting an extensive green roof, there are still plenty of choices to add color and variety to your roof. Here’s a list of plants that are suitable for a growing layer of 6 inches.
Alpine Aster
Latin Name: Aster Alpinus
Plant Type: Wildflower
Hardiness Zone: 4-7
Appearance: Bright purple flowers shaped like shasta daisies
Height: 8 to 12 inches
Climate Conditions: Alpine asters perform best in poor, well-drained soil. While they don’t need much water, they require full sun and don’t do well in high-moisture substrates.
Benefits: The beautiful, drought-resistant flower attracts butterflies and thrives in poor soil.
Season: Late spring and early summer
Lifespan: Perennial
Birdsfoot Trefoil
Latin Name: Lotus corniculatus
Plant Type: Wildflower
Hardiness Zone: Zones 4 to 8
Appearance: The low-lying plant has rich, bright yellow flowers. Their flowers transform into seed pods at the end of the blooming season.
Height: 12 to 24 inches
Climate Conditions: Birdsfoot trefoil grows low to the ground and dislikes shade. It requires full sun to thrive.
Benefits: Attracts pollinator insects such as bees and butterflies
Season: Flowers bloom in the summer
Lifespan: Perennial
Blue Sedge
Latin Name: Carex flacca or Carex glauca
Plant Type: Grass
Hardiness Zone: 5-9
Appearance: The blue-green grass forms in a rounded, bushy cluster
Height: 6 to 12 inches
Climate Conditions: Although drought-tolerant, blue sedge requires moist soil. It is a resilient plant that thrives in all kinds of soils and climates. It can survive in partial sun and shade.
Benefits: Blue sedge is low maintenance. The hardy, drought-resistant plant draws birds to your roof that love to eat the plant’s seeds.
Season: Growing season is spring through fall. A semi-evergreen plant, they are dormant in the winter, but provide green color year-round.
Lifespan: Approximately 10 years
Bowles Golden Sedge
Latin Name: Carex elata “Aurea”
Plant Type: Grass
Hardiness Zone: 5-9
Appearance: A yellow-green bushy grass
Height: 12 to 36 inches
Climate Conditions: It requires moist soil and performs well in humid or rainy areas. It grows in partial or full sun, requiring at least four to six hours of direct sunlight a day.
Benefits: Low-maintenance; deer resistant
Season: Blooms in the spring
Lifespan: Approximately 10 years
Common Thyme
Latin Name: Thymus vulgaris
Plant Type: Herb
Hardiness Zone: 5-9
Appearance: A member of the mint family, common thyme is a bushy shrub with small, vivid green leaves decorating stems. It blossoms with lilac and pink flowers.
Height: 6 to 12 inches
Climate Conditions: Thyme loves full sun and dry soil. It does not require a lot of watering.
Benefits: The evergreen plant offers an aromatic scent. The flowers attract pollinators like honeybees and butterflies. The herb is edible and offers medicinal benefits, helping to alleviate symptoms such as:
- Cough
- Dementia
- Diarrhea
- Hair loss
- Headaches
- Sore throat
- Stomachache
Season: Flowers bloom in early summer
Lifespan: Perennial with a lifespan of around four to six years
Gold Moss Stonecrop
Latin Name: Sedum acre
Plant Type: Succulent
Hardiness Zone: 3-8
Appearance: Gold moss stonecrop is a low-growing evergreen with sunny yellow flowers. Its rounded leaves are dark green.
Height: 2 to 5 inches
Climate Conditions: Gold moss stonecrop needs well-drained soil with regular waterings. It grows in full sun.
Benefits: Good for cold climates; attracts butterflies; deer resistant
Season: Flowers bloom in the summer
Lifespan: Perennial plant that can last for several decades
Gold Sedum
Latin Name: Sedum aldophii
Plant Type: Succulent
Hardiness Zone: 8-11
Appearance: Gold sedum has thick golden-green leaves formed in a rosette pattern. During the flowering season, they produce white, star-shaped flowers.
Height: 10 to 12 inches
Climate Conditions: Native to Mexico, the drought-tolerant plant grows in dry, shallow substrates. It performs best in well-drained, sandy soils with partial or full sun. It doesn’t require many nutrients, but it does require at least six hours of sunlight a day.
Benefits: Lightweight; low maintenance; flowers attract bees and pollinating insects
Season: Blooms in early spring; grows from spring to fall
Lifespan: Perennial
Houseleeks
Latin Name: Sempervivum
Plant Type: Succulent
Hardiness Zone: 3-9
Appearance: Thick, plump leaves are arranged in a rosette spiral pattern. They come in many colors. There are many different types of houseleeks, but cobweb species are the most popular for green roofs.
Height: 3 to 12 inches
Climate Conditions: Houseleeks, known as hen and chicks, survive in tough weather conditions, including cold areas. They thrive in poor soil and even grow out of rocks or bricks. They require full sun.
Benefits: With a name that appropriately translates to “live forever,” houseleeks indeed are always alive. The hardy evergreen survives through the winter, making it a great addition for your rooftop garden.
Season: Flowers bloom all through the summer months
Lifespan: Perennial
Ice Plant
Latin Name: Delosperma
Plant Type: Succulent
Hardiness Zone: 4-9
Appearance: Flowers come in a variety of colors: purple, pink, red, orange, and yellow. Ice plants usually spread out about 1 to 2 feet.
Height: 3 to 6 inches
Climate Conditions: Ice plants prefer dry, well-drained soil and won’t tolerate moist soil. They require six to eight hours of sunlight each day. Despite the name, ice plants perform poorly in cold climates.
Benefits: Low-maintenance; don’t require much water
Season: Flowers bloom in late spring to early autumn
Lifespan: Perennial
Meadow Saxifrage
Latin Name: Saxifraga granulata
Plant Type: Wildflower
Hardiness Zone: 4-9
Appearance: Tall, long-stemmed plants with snow white flowers.
Height: 6 to 20 inches
Climate Conditions: The grassland plant thrives in fertile soil, full sunlight, and regular waterings. They dislike areas with too much shade. Too much rain can rot the roots.
Benefits: Pollen and nectar attract pollinating insects
Season: Flowers bloom from April through June
Lifespan: Perennial
Mondo Grass
Latin Name: Ophiopogon japonicus
Plant Type: Grass
Hardiness Zone: 6-11
Appearance: Grassy plant with lilac or white flowers. Mondo grass, also known as monkey grass, comes in a variety of colors from yellow-green to blue-green.
Height: 6 to 10 inches
Climate Conditions: Ideal for cold climates. Requires moist soil and full or partial shade. Can survive almost any soil.
Benefits: Low-maintenance; deer resistant; evergreen
Season: Summer
Lifespan: Perennial
Oregano
Latin Name: Origanum vulgare
Plant Type: Herb
Hardiness Zone: 5-10
Appearance: Oval green leaves with purple, pink, or white flowers.
Height: 12 to 24 inches
Climate Conditions: Oregano thrives well-drained soil. Place in full sun or in partial sun for hot climates.
Benefits: Both the leaves and flowers are edible. Aside from providing an overall health boost, oregano offers medicinal benefits for alleviating:
- Asthma
- Aching muscles
- Colds
- Cramping
- Diarrhea
- Indigestion
The flowers offer an aromatic fragrance and attract pollinators. Trimming oregano fosters bushier growth rather than vertical growth.
Season: Flowers bloom in summer
Lifespan: Perennial
Sea Thrift
Latin Name: Armeria maritima
Plant Type: Wildflower
Hardiness Zone: 4-8
Appearance: The coastal plant has grass-like leaves. During the blooming season, rounded clusters of pink, purple, or white flowers top long, thin stems.
Height: 6 to 12 inches
Climate Conditions: Sea thrift is best suited for climates near the ocean, as the plant thrives in coastal areas. It grows in shallow, sandy soil. It requires partial or full sun, dry soil, and not much water.
Benefits: Adapts to harsh conditions; attracts butterflies
Season: Flowers bloom in the spring
Lifespan: Perennial
Tree Aeonium
Latin Name: Aeonium arboreum
Plant Type: Succulent
Hardiness Zone: 9-11
Appearance: The shrub-like plant features bright green rosettes on tall, trunk-like brown stems.
Height: 36 to 60 inches. They have a wide size range because there are so many different varieties and types of tree aeonium.
Climate Conditions: They like partial or full sun and sandy, dry soil.
Benefits: Adds vertical depth to your roof
Season: Evergreen that lasts all year
Lifespan: 3-10 years
Two Row Stonecrop
Latin Name: Sedum spurium
Plant Type: Succulent
Hardiness Zone: 3-9
Appearance: Flowers with star-shaped blossoms in shades of pink, red, or white. The grounded green leaves turn red on the edges in cold climates.
Height: 4 to 6 inches
Climate Conditions: Two row stonecrops last in just about any type of soil. They love a lot of sunlight and well-drained soil.
Benefits: Two row stonecrop retains a lot of water, making them fire resistant.
Season: Blooms late in the year, from the end of summer through autumn
Lifespan: Perennial
White Stonecrop
Latin Name: Sedum album
Plant Type: Succulent
Hardiness Zone: 3-8
Appearance: A tangle of stems and blossoms, white stonecrop grows low to the ground and has a shallow root system. Their star-shaped flowers are pink or white. Their foliage is normally bright green, but in cold weather, the leaves turn a reddish-brown hue.
Height: 3 to 6 inches
Climate Conditions: White stonecrop performs best in full sun and well-drained soil. They only require a thin layer of soil to grow in.
Benefits: Flowers attract pollinators; low maintenance; drought-resistant
Season: Flowers bloom in the summer
Lifespan: Perennial
Widow’s Cross
Latin Name: Sedum Pulchellum
Plant Type: Succulent
Hardiness Zone: 6-9
Appearance: The pink or green flowers of widow’s cross grow in armlike clusters, almost looking like a starfish.
Height: 4 to 12 inches
Climate Conditions: The hardy, drought-resistant sedum withstands dry conditions. It needs a lot of sun and dry soil.
Benefits: Drought-resistant; low maintenance
Season: Flowers bloom in the spring and summer months
Lifespan: Annual or perennial
Best Plants for Intensive Roofs
Intensive roofs accommodate a large number of plants, even large plants like shrubs and trees. Below are a couple of options for plants homeowners can consider putting on their intensive roof. Keep in mind that all plants that are suitable for an extensive roof will work on semi-intensive and intensive green roofs as well.
Allium
Latin Name: Allium schoenoprasum
Plant Type: Wildflower
Hardiness Zone: 3-9
Appearance: Purple flowers bloom in spherical clusters on top of long green stems
Height: 6 to 12 inches
Climate Conditions: Tolerates a little shade, but thrives in full sun
Benefits: Attracts bees and butterflies; drought-tolerant
Season: Flowers bloom in the late spring and early summer
Lifespan: Perennial
Cosmos
Latin Name: Cosmos bipinnatus
Plant Type: Wildflower
Hardiness Zone: 9-11
Appearance: The wide petals are arranged in a bowl-shape and come in many colors: gold, white, pink, orange, yellow, red, and chocolate. The large blooms top long, grasslike stalks.
Height: 2 to 5 feet
Climate Conditions: Cosmos love full sun and dry soil. They should get six to eight hours of direct sunlight a day. They are capable of surviving droughts, but they will produce more flowers if they are regularly watered.
Benefits: Attracts bees, butterflies, and birds; drought tolerant
Season: Blooms in the summer through autumn
Lifespan: Annual
Deer Fern
Latin Name: Blechnum spicant
Plant Type: Fern
Hardiness Zone: 5-8
Appearance: Also known as hard fern, it has long, feathery green fronds. It is a nonflowering plant.
Height: 18 to 24 inches
Climate Conditions: Deer fern is a hardy plant that grows naturally in woods and forests and so requires partial to full shade. It thrives in acidic, humus-rich soil that is frequently moist.
Benefits: Evergreen
Season: Green all year
Lifespan: Perennial
Fleabane
Latin Name: Erigeron
Plant Type: Wildflower
Hardiness Zone: 2-9
Appearance: Fleabane is a type of daisy that comes in multiple pastel colors, such as white, yellow, pink, and lilac. Their colorful petals are centered on a yellow button middle.
Height: 1 to 4 feet
Climate Conditions: Fleabane thrives in open spaces. It does best in dry soil in full sun but can do with partial sun.
Benefits: Flowers attract butterflies and moths; deer resistant; low maintenance
Season: Blooms in late spring to early autumn
Lifespan: Annual, biennial, or perennial
Lavender
Latin Name: Lavandula
Plant Type: Herb
Hardiness Zone: 5-10
Appearance: Flowers can be lavender purple, rich bluish purple, light pink, or white
Height: 2 to 3 feet
Climate Conditions: Lavender does well in dry conditions. It needs about six to eight hours of direct sunlight each day.
Benefits: Sweet fragrance; drought and heat tolerant; doesn’t require much watering
Season: Blooming season is June through August
Lifespan: Perennial
Redclaws
Latin Name: Escallonia
Plant Type: Shrub
Hardiness Zone: 7-10
Appearance: Large green-leafed shrub that blooms with white, pink, or red flowers
Height: 5 to 8 feet
Climate Conditions: Redclaws love full sun and warm environments. They thrive in fertile, well-drained soil. They are good for coastal areas.
Benefits: Attracts bees
Season: Evergreen foliage; flowers bloom in May through August
Lifespan: Perennial
Rosemary
Latin Name: Salvia rosmarinus or Rosmarinus officinalis
Plant Type: Herb
Hardiness Zone: 7-10
Appearance: Needle-thin, erect leaves grow on woody, spindly stalks. The shrub flowers in blooms of white, pink, blue, or purple.
Height: 1 to 6 feet
Climate Conditions: Loves a lot of sunlight and well-drained soil
Benefits: Pleasant pine-scented fragrance; evergreen; leaves produce essential oils; attracts pollinating insects such as bees and butterflies; used in cooking
Rosemary also has medicinal properties that help with:
- Digestion
- Hair growth
- Memory
- Mood
- Muscle pain
Season: Spring through summer
Lifespan: Perennial
Verbena
Latin Name: Verbena
Plant Type: Wildflower
Hardiness Zone: 8-11
Appearance: Their flowers grow in clusters and are various shades of purple and blue, such as deep blue-violet and lavender. They can also be shades of pink, white, and red.
Height: 1 to 4 feet
Climate Conditions: Verbena requires at least six hours of full sun each day and well-drained soil. Although drought-tolerant, they do best with regular watering. Soggy soil can be harmful to verbena.
Benefits: Low maintenance; attracts butterflies and hummingbirds
Season: May to October
Lifespan: Annual or perennial
Yarrow
Latin Name: Achillea millefolium
Plant Type: Herb
Hardiness Zone: 3-9
Appearance: Tall flowering plant with pink and white flowers
Height: 24 to 48 inches
Climate Conditions: Yarrow requires water regularly, so the wildflower might not survive droughts or extended dry periods without being watered. Yarrow needs a deeper growing medium than other plants might.
Benefits: Yarrow is sweet-smelling, edible, and attractive to butterflies.
It has medicinal benefits that help with:
- Blood circulation
- Cramps
- Indigestion
- Inflammation
- Wounds
Season: Flowers bloom in spring, summer, and fall
Lifespan: Perennial
FAQs About Plants for a Green Roof
Aside from evergreens, most plants will go dormant and come back to life in the spring.
Green roofs, with all the layers and foliage, act as insulation and keep in the heat during the winter.
Sedum roofs provide a habitat and food source for wildlife and insects to enjoy. During the flowering season, sedums attract pollinating insects such as butterflies and bees.
You do not have to mow a green roof. It depends on the type of green roof and your personal tastes. If an intensive green roof is lawnmower-accessible, than homeowners can mow the grass on their roof if they want to.
Ready to Start Your Green Roof Project?
It’s up to you to decide on the perfect blend of grasses, wildflowers, succulents, and shrubs for your roof and for your personal tastes. Now that you know some of the best plants for a green roof, it’s time to get your roofing project started.
If you are planning to install a green roof on your home or looking for a pro for other roofing services, find a roofing professional near you today.
Main Image Credit: Ryan Somma / Wikimedia Commons / CC BY-SA 2.0
