Choosing the Best Native Plants for Rooftop Gardens

A rooftop garden can make a building much more pleasant.  These gardens keep a building cooler in the summer and warmer in the winter.  They improve the air quality, extend the useful life of a roof, and add beauty and color to urban areas.

Rooftop gardening is primarily done with buildings that have a flat roof, although sodding the roof and planting flowers can be done on slanted roofs.  Before buying your plants, it is important to make sure the rooftop can carry the extra weight of a garden.

Condition of the Roof

While it is possible to construct a rooftop garden on a normal city roof, it is not ideal.  You have to take into account all the roof’s flaws.  Water seeping in from the roof, roots growing into the roof, or other damage is common.

The best time to construct a rooftop garden is when the roof is being replaced or built.  This allows you to incorporate a water-proof membrane over the hard roof surface to protect the building below.  A root-resistant layer keeps roots from growing through the water membrane, creating leaks.

Structural Capacity of the Roof

Soil weighs a lot, especially when wet.  Add plants and the framing for each bed and the weight of a rooftop garden adds up.  You must hire a structural engineer or architect to examine the roof and decide how much additional weight the rooftop can support.  If the roof cannot take much weight, you may be limited to a few containers of native plants that live off of rainfall.  You can retrofit the roof to carry additional weight, but it is costly.

If the building is under construction, you can design the roof to hold a rooftop garden.  Installation is easier when it is a part of the construction, too, since cranes can lift the materials for the garden onto the roof without having to go through the elevator or stairs.

Access to the Roof

Access to the roof includes getting the garden supplies up to the roof.  Walking up several flights of stairs with lumber, soil, and fertilizer stops being fun very quickly.  In addition, most fire codes require two ways to exit the roof in case of fire.  This can be a fire escape, stairs, or access to the next building over.  Many rooftop gardens include a small greenhouse to start seeds in.  Greenhouses need electricity and the whole garden will need water so make sure those are available before planning yoiur garden.

Weight of the Garden

rooftop garden

An architect or landscape design architect needs to determine the weight of the kind of garden you want on your roof.  This takes into consideration the weight of water, soil, containers, heaters, cooling, ventilation, and, if it snows where you are, snow load.  You don’t want to get this wrong or your rooftop garden may become a basement garden.  You also have to consider how many people can be on the roof at one time.  Here are some estimates that the City of Chicago published for rooftop gardens.

  • Water stored in tanks weighs about 8 lbs/gallon.
  • Extensive green roof systems weigh about 20-34 lbs/ft2.
  • Intensive green roof systems weigh about 80-150 lbs/ft2.
  • The City of Chicago Municipal Code requires at least 30 lbs/ft2 for the design snow load.

An extensive green roof system is one where you use pots and some hardy plants for a garden.  It does not need as much infrastructure as an intensive green roof system.  An intensive green roof system is most like a raised bed garden on a normal lot.

Cost

A green roof system costs about 50% more than a conventional roof.  However, it extends the life of the roof by at least 50%, keeps cooling and heating bills lower, and looks nicer than a conventional roof.

Your budget needs to include the containers, cost of a structural engineer or architect for determining roof load and overseeing construction, safety features such as rails around the edge of the roof, transportation of materials to the roof, soil, an irrigation system, and the cost of permits and fees.  You should also include maintenance costs.  Some locations offer cost sharing if you put in a rooftop garden that meets their requirements because of the lower energy costs and pollution, but you will need quite a sum to get started.

Designing a Green Roof System

A green roof system has many components.  The bottom layer is the roof deck.  A waterproof membrane is next, then a root barrier to stop the roots from growing into the waterproof membrane.  A layer of insulation comes next, followed by a drainage layer that is gravel.  This gives the water from rain, snow, and irrigation of the garden a way to drain out of the growing media above it.  Next there is a filter mat that keeps the growing media from running out with the water as the garden drains.  Finally, there is the growing media, the plants, and a wind blanket to hold the growing media on the roof until the plant roots grow into it and prevent the wind from blowing it away.

Irrigation

Using plants native to the region you live in will decrease the need for irrigation.  However, there are times even drought tolerant plants need help, so you should provide a way to water your plants.  Drip irrigation is the best option, but a spigot for hand watering is the cheapest.  You will need to hire a plumber to extend the water system in the building to the roof.

Drainage

Drainage is essential to prevent the garden from damaging the roof and building.  Poor drainage not only causes the roots of your plants to rot, it adds substantial weight to the roof.  Most rooftop drainage systems can be used with minor tweaks.  Again, consult with a structural engineer or architect for help making sure your rooftop garden has good drainage.

Choosing Plants and Growing Media

Soil is heavy.  Most rooftop gardens use light weight growing media for their plants to grow in.  Typically, it is compost and lightweight, porous material that absorbs water and then releases it back to the plant as the plant needs it.  This medium is often referred to as potting mix, as it contains no soil.

Native plants fare best in rooftop gardens because they are adapted to the amount of rain the area receives.  Pick plants that can tolerate the wind, which can be substantial if the building is very tall.  Pick plants that are happy in poor, dryer soil so you do not have to fertilize them much.  You will have to water the plants the first year at least once a week until they are established.  The wind dries the soil and plants quickly, so a plant will require more water than the same plant in a garden on a regular lot.  Prairie plants such as purple coneflower, black-eyed susan, and blanket flower, since they can handle the wind better than something ephemeral, like a Virginia bluebell.

Maintenance

Plants need tending in a rooftop garden, just as if it were ground level.  Drains and gutters on the roof will need to be inspected more often than roofs without a garden.  Larger plants and trees will have to be pruned to prevent branch breakage in the wind.

We Can Help

TN Nursery specializes in native plants from across the United States and Canada.  Our specialists can answer your questions about choosing plants for your rooftop garden.  Simply call us at 931.692.7325 to get started.

Coneflower Plant - TN Nursery

Purple Coneflower

Echinacea plants like purple coneflower (Echinacea purpurea) are favorites in the garden for their beauty, ease of maintenance, and hardiness. They’re perfect for those who enjoy an attractive, pollinator-friendly perennial. Purple Coneflower Echinacea Plants are extremely easy to cultivate They prefer good soil and full sun but will also tolerate some shade. Planting them is simple, you simply make a hole rather than bury the root ball in the soil and water it. Once established, they do not require a lot of maintenance or attention, not even watering when it’s still dry. They are drought-tolerant and pest-resistant and attract pollinators like bees and butterflies.  Seasonal Beauty and Blooming Cycle  They are known to bloom throughout the summer and late fall. The purple-pink petals of each bloom cluster around a coppery-orange cone. Winter dries up the flowers, and decorative seed heads appear in winter to attract birds. The bloom season lasts many weeks after summer arrives. Even into late fall, you will see birds and monarchs feasting off these plants.  Shape and Longevity of Echinacea Plants Purple Coneflowers are tall, graceful plants growing two to four feet tall. They are striking because of their daisy flowers and their somber green leaves. The perennials are perennial and can endure for decades when cared for appropriately, thus offering an excellent, stable, and durable option for any garden.  

Black Eyed Susan - TN Nursery

Black Eyed Susan

Black Eyed Susan has vibrant yellow petals and dark, contrasting centers and is a popular and delightful addition to any landscaping project. This native North American wildflower offers a host of pleasing attributes that make it a sought-after choice for gardens and outdoor spaces. From its adaptability to its visual appeal and ecological benefits, it stands out as a versatile and attractive plant.  Black-Eyed Susan (Rudbeckia Hirta) Is A Long-Blooming Perennial  The Black-Eyed Susan or Rudbeckia Hirta is a beautiful and popular flower that blooms each year in North America. With yellow flowers surrounding a dark circular center, this plant serves an aesthetic purpose in any landscape and draws in bees and butterflies. Due to its hardiness and versatility, the plant is suitable for growing in the garden for beginners and professionals.  The Black Eyed Susan is valued for ornamental purposes and its contribution to the maintenance of ecosystems. Moreover, black-eyed susan plants for sale have stunning flowers that can be added to your garden for curb appeal. Features of Black Eyed Susan Plant The Black-Eyed Susan has bright yellow petals with a dark brown or black Eye in the middle, which makes it a vivid plant that would look great in any garden.  This plant attracts bees, butterflies, and many other beneficial insects, so it should be included in any pollinator garden. The black-eyed susan plant is relatively adaptable. It does well in arid conditions and simple soil types, making it a perfect pick for any low-maintenance garden. Black Eyed Susans Are Excellent Pollinator Plants It prefers regions receiving full or partial sun exposure. It has a growth habit of 2 to 3 feet tall with a similar width, enhancing the green appearance of areas where it is grown. This plant does not need much attention once established and usually grows well. It is relatively immune to many garden pests and diseases. Growers of black-eyed susan plants can also contribute to habitat and care for one's patch of land by offering food for pollinators and other more valuable insects. Black Eyed Susan Perennials Returns Every Spring and Summer Season Buy black-eyed susan plants and add these beautiful flowers to your garden, like our other popular ornamental plants, such as echinacea, shasta daisy, or coneflower plants. Where Does Black Eyed Susan Grow Best  Black-eyed Susans do well in regions of full exposure to the sun. Ensure they are exposed to a minimum of six hours of sunshine every day. They like well-draining soils and will grow in a range of soil types.  What Do Black Eyed Susans Symbolize  Black-eyed Susans symbolize encouragement, motivation, and justice. Their bright yellow color with a black center is linked with positivism and strength, perfect when integrated into any garden.  What Is The Best Fertilizer To Grow Black Eyed Susans Black-eyed Susans prefer a slow-release fertilizer, preferably a 10-10-10 N-P-K ration. Use it sparingly as they grow because these plants are not heavy feeders.  How Tall Do Black Eyed Susans Get  They are perennials that range in height between 1 to 3 feet, depending on their type. They provide great accents to borders and garden landscapes.  How Long Does It Take To Grow Black Eyed Susan  Black-eyed Susans can take from 60 to 90 days to bloom after germination from seeds. The plants come back year after year, blooming mid to late summer and continuing well into early fall.

Blanket Flower - TN Nursery

Blanket Flower

Blanket Flower is a perennial wildflower known for its vibrant, daisy-like blooms with red or yellow petals and dark center disks. Often found in prairies and gardens, it attracts pollinators and adds color to landscapes. This plant is the perfect choice when craving warmth. This radiant wildflower with an extended blooming season will light up your garden with a kaleidoscope of glowing colors.  Blanket Flower (Gaillardia aristata) Thrives In Drought and Full Sun Blanket Flower, or Gaillardia, is a sun-loving perennial with stunning two-toned daisy-like blooms. The name "Blanket Flower" interestingly comes from its warm yet vibrant red and yellow blooms, which are similar to the blankets Native Americans make.  This wildflower plant belongs to the Asteraceae (daisy) family and is native to North and South America. It is commonly found in Arizona, California, Arkansas, Indiana, Iowa, and Colorado. Blanket Flowers Resembles Daisy Perennials While it may resemble a daisy, blanket flowers are related to sunflowers and brighten up the dullest landscapes. The plant is usually paired with other drought-tolerant plants and showy grass to enhance the visual interest of the entire landscape. Moreover, blanket flowers for sale come in various warm shades and a few fabulous shades, making them a statement piece in the garden. Features of Blanket Flower Plant The plant grows best in total sun exposure, sandy areas, and poor soil. The poorer the soil, the more blooms it will grow.  The blanket flower features blooms in various colors, such as orange, purple, red, yellow, and White. Depending on the season, the foliage can be either blue-green or gray-silver.  This ornamental plant can reach 1-3 feet in height and 1-2 feet in width. Water the plant every other day during the first growing period until you see flowers. Once established, it's easy to care for and does not require regular watering to stay alive.  The Blanket flower is an ecosystem booster, so it loves pollinators, birds, and other wildlife Though people with sensitive skin may experience skin irritation, the plant is non-toxic to humans and animals. This vibrant perennial pairs well with low-maintenance and drought-tolerant perennials, like Butterfly Weed, Yarrow, and Daylily. So, along with blanket flower plants for sale, check out other companion plants at T.N. Nursery.  How Long Does A Blanket Flower Live  Blanket flowers live approximately 2 to 3 years in optimal climates and conditions. However, they self-seed and germinated every year and manifested their presence around the garden.  Why are they called Blanket Flower  They are named so due to the resemblance of their multi-colored and beautiful flowers to a patterned blanket. The flowers have lush reds, oranges, and yellows, providing a warm, bright view all through the season.  Does Blanket Flower Multiply  Indeed, blanket flowers reproduce both by seeds and by rhizomes. They can form larger clusters in time, giving the garden excellent bloom spots more often.  Does Blanket Flower Need To Be Deadheaded  Deadheading is not mandatory for growing blanket flowers, but this practice promotes more blooms and keeps the plants neat. Blanket flowers grow in well-drained soils and prefer minimal fertilization. During spring, you should only apply a small portion of a balanced fertilizer to encourage growth. Too much fertilizer may hamper the bright blooms.

Virginia Bluebell - TN Nursery

Virginia Bluebell

Virginia Bluebell is a spring-blooming wildflower native to the United States recognized for its delicate, bell-shaped, sky-blue flowers forming clusters and carpeting the forest floor in early spring. It is a captivating perennial plant that offers numerous benefits when incorporated into landscaping designs. Its enchanting appearance and adaptability have made it a favorite among gardeners and landscapers. Virginia Bluebell (Mertensia virginica) produces Sky sky-blue bell-shaped flowers These flowers start as shades of pink and gradually transition to a soothing sky-blue hue, creating a stunning gradient effect that adds a touch of elegance to any landscape. The lush green foliage further complements the vibrant blooms, enhancing the overall visual impact. Besides its visual appeal, it is positively adjustable to various soil types, making it a perfect option for landscaping projects in multiple environments. Its preference for partially shaded to fully shaded areas makes it ideal for underplanting trees or placing them along the edges of woodland gardens. This versatility allows landscapers to create visually appealing designs catering to light conditions. Another benefit of incorporating them is their role in supporting local ecosystems. These plants are attractive to pollinators such as bees and butterflies, making them valuable contributors to biodiversity. By attracting these pollinators, they aid in reproducing nearby plants and promote a healthier ecosystem within the landscape. They also require little maintenance, making them appealing to amateur and experienced gardeners. Once established, they require minimal care, allowing landscapers to focus on other design aspects. In conclusion, perennial plants offer a range of benefits that enhance the overall appeal and ecological value of landscaping projects. With their captivating appearance, adaptability to various environments, support for local wildlife, and low maintenance needs, these perennial plants are a valuable addition to any landscape design seeking a harmonious blend of beauty and functionality. Virginia Bluebell Is Known For Its Beauty  The Virginia Bluebell, or Mertensia virginica, is a stunning and delicate native wildflower that graces eastern North America's woodlands and meadows. This perennial plant, belonging to the Boraginaceae family, is renowned for its enchanting beauty and is often considered one of the most striking spring wildflowers in its native range. Standing at heights 1 to 2.5 feet, the wildflower is a herbaceous plant that emerges from the forest floor early to mid-spring. Its growth cycle is a true spectacle as it undergoes a remarkable transformation. Initially, the plant's lance-shaped leaves are tinged with an attractive reddish-purple hue, but as they unfurl, they transition to a soft, gray-green color, creating a stunning contrast with its vibrant blue flowers. The Virginia Bluebell Has Mesmerizing Fairy-Like Flowers The flowers themselves are the main attraction of the plant. They are composed of clusters of pendulous, trumpet-shaped blooms that are a breathtaking shade of sky blue or pale pink, depending on the soil conditions. These blossoms are unique because they start as pink buds, gradually shifting to their iconic blue hue as they mature. The floral clusters adorn the plant's upright stems, creating a sea of blue that sways gently in the spring breeze. One of their most remarkable aspects is their ability to thrive in shaded woodland areas. They are often found in the dappled sunlight beneath deciduous trees, creating a serene and ethereal ambiance in these natural settings. Their preference for moist, rich soils ensures they are frequently spotted along stream banks and low-lying areas. Aside from its visual appeal, it plays an essential ecological role. They provide nectar for early-emerging pollinators like bees and butterflies, helping to kickstart the pollination process for various plants in their ecosystem. The Virginia Bluebell symbolizes grace and fleeting beauty in the natural world.  Its striking blue flowers and unique life cycle make it a beloved harbinger of spring, enriching the landscapes it graces and captivating all who have the privilege to witness its brief but glorious bloom. What is the best fertilizer for Virginia Bluebells Virginia bluebells grow best under a light mulch of organic compost or the use of slow-release balanced fertilizer in early spring. As these plants prefer soils with natural fertility, fertilization may not be compulsory.  How often should I water Virginia Bluebells?  Irrigate Virginia bluebells often during their growing period to ensure the soil is wet but not saturated. They need less water once they have been established.  Can I grow Virginia Bluebells indoors Virginia bluebells are best suited for the landscapes but can be started inside in containers. These plants require only moderate lighting conditions and should be shifted outside only when weather permits.  What is the lifespan of Virginia Bluebells?  The Virginia bluebells are perennials, meaning that they will grow back year after year. If well taken care of, they can propagate and grow well and will do very well when placed in shaded garden sections where they will bring beautiful displays.  Where do Virginia Bluebells grow best Virginia Bluebells prefer moist, well-drained soil and in light shade or fully shaded conditions. They prefer a habitat similar to woodland settings.

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