What Is A Rooftop Garden? (Plus 6 Plants To Include)


I know you’ve heard about green rooftop bars or maybe you’ve seen pictures of the Phipps Conservatory Edible Rooftop Garden in Pittsburgh, Pennsylvania. You might be wondering what all the fuss is about, and how on earth someone can grow a full garden on concrete?

A rooftop garden is – you guessed it – green space on a rooftop or exposed building. Rooftop gardens are commonly found in urban spaces, atop commercial and residential buildings. Green roofs have been around since the dawn of civilization, and modern rooftop gardens come in all sizes and shapes to meet a variety of needs. 

Different Types Of Rooftop Gardens

New York Decks, a company that builds and installs rooftop gardens, defines them as

“a garden on the rooftop of a building, man-made green spaces on the topmost level of residential and commercial structures.”¹

“Rooftop Garden: Definition, misconceptions, and benefits,” New York Decks, 26 Feb 2020, https://www.newyorkdecks.com/rooftop-garden-benefits/
rooftop garden London
A rooftop garden is a a man-made green space on the rooftop of a building.

The company further characterizes rooftop gardens in one of three categories:

  • extensive
  • semi-intensive
  • intensive¹

Extensive gardens are more akin to green roofs – these gardens typically consist of succulents, sedums, mosses, and other small plants. 

moss on statue
Moss is one option you can include in an extensive rooftop garden, which is more like a green roof.

The primary function here is not so much a space for people to use. Rather, the root systems of the plants catch excess water and help preserve the life of the roof.

Extensive gardens are designed to be low-maintenance, requiring no more irrigation than regular rainwater. Extensive gardens aren’t cheap, but they are the least expensive rooftop gardens to build.

Intensive gardens, on the other hand, are designed to look like a park or a community garden – these are spaces intended for people to spend time. Rooftop vegetable gardens are usually of the intensive style, and some gardens even fruit trees and shade trees!

rooftop garden London 2
Intensive rooftop gardens often use shrubs or trees to provide shade for visitors.

Intensive gardens are by far the most expensive rooftop gardens to build, requiring contractors to assess the building’s existing structural strength and areas that may need more support.

Intensive gardens do require a significant amount of maintenance – as much as a ground-level garden. Irrigating an intensive rooftop garden is no small task.

There are a few creative ways to make the chore of irrigating a rooftop garden easier – try installing a rain barrel and drip irrigation, or have the contractor build a reservoir into the rooftop garden.

Striking a middle ground between the three green roof types is the semi-intensive rooftop garden – just perfect for decorative shrubs, bushy flowers, and some herbs and vegetables.

pole beans (green beans)
A semi-intensive rooftop garden may include vegetables (such as pole beans) as well as decorative shrubs and flowers.

There is another kind of rooftop garden, the type most easily built and readily customizable – the container garden

Advantages (& Disadvantages) Of Rooftop Gardens

There are so many benefits to building rooftop gardens and green roofs.

Structural

Despite common belief, rooftop gardens don’t contribute to roof and building deterioration if they’re built correctly, with the appropriate structural support in place.

rooftop garden high rise
A rooftop garden (like the one on this high rise), when installed properly, can help to protect waterproofing materials on the roof surface.

Rooftop gardens actually protect the waterproofing materials on buildings and rooftops, prolonging the life of the building by softening the blows of natural weathering processes. Once established, green roofs actually collect excess water and lessen its negative impact by better distributing the water flow.

Aesthetic

Can we all agree that rooftop gardens are absolutely beautiful? Rooftop gardens break up the monotony of the concrete and bland building materials of the city, while making good use of spaces that typically go unused.    

city
Most cities can use a little more green space, and a rooftop garden provides it without taking up valuable real estate.

Accessibility

Let’s be honest – not everyone has property or even a yard. So many people in apartments and condos could benefit from having a rooftop garden! Everyone should have access to a space where they can grow food for themselves and their families.

It’s a proven fact that people need plants. Even the color green has a calming effect on our emotions, and being outside in nature often works wonders for our mental and physical health.

pole beans
Being close to nature and green growth can help you to relax after a busy day in the city.

Rooftop gardens provide a space to grow food, but they can provide something much more than that. Rooftop gardens are a place to gather outside, to enjoy the sunshine, and picnic or play games with loved ones.  

Environmental

If the first three reasons weren’t enough to convince you of rooftop gardens, let this final reason catch your attention – rooftop gardens have a positive environmental impact.

Whether you have a container garden or you install an intensive rooftop garden, you are creating habitat for insects and birds. No matter how small your garden is, by cultivating plants that pull carbon dioxide from the air, you help improve the air quality around you. 

Dwarf Umbrella Tree
If you have a small indoor plant in your apartment, you might find a place for it on a rooftop garden.

Finally, the greenery on green roofs actually helps insulate the building itself – keeping the interior both warmer in winter and colder in summer, while simultaneously cutting down on energy use.

There have even been scientists who speculate that if enough buildings install green roofs, the rooftop gardens would work to lower the temperature of the city itself, as well as drastically reduce its energy use. 

Disadvantages

As with anything, there are a few obstacles and disadvantages of rooftop gardens – the main one being the cost of the project.

The cheapest way to build a rooftop garden is to use raised beds and containers, but even then lumber prices are so high that it’s no small feat. Professionally installed green roofs and rooftop gardens, as you can imagine, are expensive. 

raised bed image homepage
Raised beds are great, but with the cost of wood going up, they are getting expensive!

Rooftop gardens also require some hoops to jump through. In some case, you’ll need permission from your landlord or the city.

Even with permission, you’ll want to make sure that your rooftop garden meets all the right codes and safety requirements. You’ll need a professional to survey the space and see if any structure will need to be reinforced or new supports added. 

The beauty of a rooftop garden is that you’ll likely have full sun for most of the day – which could be a problem for some plants. Rooftop gardens are more likely to suffer from heat and wind stress since neighboring buildings (and the streets below) will reflect heat and channel wind.

sunlight through trees
Plants on the ground get shade from trees, but rooftop gardens will not – unless you plant some of your own trees to provide shade.

Be aware that the exposed placement of your rooftop garden is also more susceptible to bad weather, so bear this in mind when choosing what plants to cultivate.

Watering is always a chore, but even more so with a rooftop garden. Have a watering plan or an irrigation system in place before you plant, or you’ll be lugging watering cans from your apartment to the roof at least once a day – sometimes more. 

Logistics Of Building A Rooftop Garden

There are a few things you want to consider when building a rooftop garden. The logistics just won’t be as easy as a ground-level garden, but even the biggest obstacles can be worked around. 

Structure & Safety

It’s worth it to hire a professional to look at your space if you’re going to be installing anything major, like extensive raised beds or multiple rain barrels.

rooftop garden city
Be sure to consider structural integrity and safety, due to the extra weight of a rooftop garden.

Even if your only intention is a container garden, you might still consider hiring an inspector (or take the time yourself) to look for any safety issues or potential problems. 

Accessibility

Next, think about the logistics of gardening in this specific area and set some realistic goals. Identify the potential problems, like:

  • How do I (and other people) access the garden?
  • How will I move plants to this area?
  • How will I carry potting soil/lumber/tools to the roof?

If the elevator is your only option for moving materials up, that’s fine – but what do you have that will make the job easier? Racks or carts?

shopping cart
An old shopping cart can help you to bring plants, soil and tools up to the rooftop garden.

Maybe schedule a moving day and recruit some of your neighbors and friends to help. 

Irrigation

There are a number of ways that you can choose to irrigate your rooftop garden. However, carting a watering can from your apartment to the rooftop probably shouldn’t be one.

rooftop garden Ebisu Atre
Make sure that you have a way to get water to the rooftop garden. This is the rooftop garden at Eribu Atre.

Consider putting in a rain barrel or two, and then hook up a gravity-fed drip irrigation system to do the rest. For more information on where to buy and how to use drip irrigation, check out this article

drip irrigation emitter
A drip irrigation system makes it much easier to keep plants watered, whether in a conventional or rooftop garden.

Maybe there’s a spigot that you can hook a watering hose up to, but even then–who foots the cost of that bill? Consider all your options and try to think outside the box for an efficient and effective irrigation system. 

Weather

Possibly the best and worst thing about a rooftop garden is that rooftops typically get full sun exposure – unless much taller neighboring buildings cast their shadows on it.

There are many plants, especially annual flowers and vegetables, that love full sun – but there are some plants that require a little bit of shade in the heat of the summer. Research crop growing needs and plant accordingly. 

rooftop garden Warsaw University Library
Some plants need shade for part of the day during the summer heat, so know your plants and their requirements.

Concrete and other urban building materials have the tendency to absorb sunlight and release heat over the course of the day.

Keep this in mind as well – the plants in your rooftop garden will probably new more frequent watering, and you’ll definitely want to wear a hat and sleeves to protect your skin from the intense sunlight.

Another thing to consider with rooftop gardens is wind. Rooftop gardens have to be able to withstand high wind and bad weather.

wind vane
Take the wind into account when planning your rooftop garden – some windscreens can help to protect your plants.

You might consider building a few windscreens in your rooftop garden, to cast some shade and protect tender plants. 

Cost

Last but not least, consider how much your rooftop garden project will cost. Unfortunately, rooftop gardens are not inexpensive projects.

rooftop garden near Pittsburgh, Pennsylvania
Rooftop gardens can get pretty expensive, so set your budget and plan accordingly.

Container gardens are cheaper than professionally-installed intensive gardens, but with either project, you’ll want to budget for the cost of plant starts or seeds, potting soil, a watering hose or drip irrigation, shovels and hoes, etc. 

6 Plants To Include In A Rooftop Garden

You can grow practically anything you want in a rooftop garden, but some varieties are more likely to thrive than others. 

When in doubt, opt for annual plants that won’t have to overwinter on top of an exposed building. If your goal is to create an edible garden, choose sun-loving vegetables and fruits that bear in their first season. 

For ground cover and ornamental plants, try growing succulents, grasses, and mosses. These low-maintenance plants don’t require much water but cover bare ground and retain moisture. 

botanical garden succulents
Try succulents, grasses, or mosses for ground cover on your rooftop garden.

The following list is not exclusive but does contain vegetables, herbs, and flowers that are particularly well-suited to rooftop gardens. 

1. Tomatoes

These sun-loving annuals are just perfect for an edible rooftop garden. Tomatoes love heat and can stand to get a little dry.

tomato plant 3-12-2021
You can start tomato plants indoors and transplant them to a rooftop garden when the weather warms up.

Just be sure to give tomatoes a trellis to climb, and tie the stems to it so that the wind doesn’t fight them too much. In about 100 days you’ll have farm-fresh tomatoes every day!

You can learn more about heirloom tomatoes here.

You can learn about more than 30 interesting heirloom tomato varieties here.

2. Peppers

Like tomatoes, peppers need full sunlight and adequate heat to fruit. With so many varieties to choose from, from hot to sweet and everything in between, you really can’t go wrong with peppers. These bushy plants thrive in containers, too.

pepper plant
Pepper plants need warm weather to thrive, and you can choose from bell, jalapeno, and other types.

You can learn about how to protect pepper plants from cold temperatures (and extend the harvest season on your rooftop garden) here.

3. Strawberries

Want fresh fruit without waiting several seasons for fruit shrubs to develop? Try planting strawberries! These easy-to-grow vines are perennial plants, coming back season after season if properly cared for.

ripening strawberries
Strawberries are a great choice if you want something sweet from your rooftop garden.

Strawberries are happy in a hanging basket or raised bed– c ontaining them in pots is even better, as strawberries have a tendency to sprawl. Some varieties fruit twice a year, in spring and fall!

4. Zinnias

No rooftop garden is complete without at least a few flowering plants – a feast for our eyes and food for urban pollinators!

Zinnia
Zinnias are beautiful and also help to attract pollinators (such as bees) to your rooftop garden.

Zinnias are easy-to-grow sun-loving annuals that produce the most striking blooms. Available in nearly every color of the rainbow, zinnias add pizazz to any rooftop garden. 

5. Basil

If you love to cook, basil is a must for any rooftop garden. This annual flourishes in full sun and summer heat and is even drought-tolerant once established.

basil
Basil is great for cooking, or fresh on tomato and mozzarella with balsamic vinaigrette.

You can learn how to protect your rooftop basil from cold here.

Pick basil often to keep it leafing out and prevent the herb from going to seed too soon. 

6. Ornamental Grasses

No, ornamental grasses aren’t edible, but they are cute – and their robust root systems keep them anchored in the ground.

Switch Grass
Try one or more ornamental grasses on your rooftop garden to prevent wind erosion.

Ornamental grasses happily spread to fill their container or bed, keeping barren soil from flying away.  

If you live in a dry climate, you can learn about 10 types of drought-tolerant grasses for your rooftop garden here.

Conclusion

Rooftop gardens are the perfect solution to urban gardening, but the logistics of running a productive rooftop garden do require some planning.

Use this article as a primer on how to get started building a rooftop garden, and then let your creativity run rampant! There’s no limit to what you can build. 

You can attract more bees (and other pollinators) to your yard with a pollinator garden – and you can learn more about how to plant one here!

I hope you found this article helpful. If so, please share it with someone who can use the information. 

If you want to read some of my most popular posts, please check out the “Best of GreenUpSide” page here. Enjoy! 

~Jonathon

Resources

¹ “Rooftop Garden: Definition, misconceptions, and benefits,” New York Decks, 26 Feb 2020, https://www.newyorkdecks.com/rooftop-garden-benefits/

About the author:
When not writing content or growing flowers in her native Virginia, you can find Sarah hiking a long-distance trail deep in the woods. Follow along with Sarah’s adventures at http://sarahcolliecreative.com.

Sarah C.

jonathon.david.madore

Hi, I'm Jon. Let's solve your gardening problems, spend more time growing, and get the best harvest every year!

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