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.
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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/
The company further characterizes rooftop gardens in one of three categories:
Extensive gardens are more akin to green roofs – these gardens typically consist of succulents, sedums, mosses, and other small plants.
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!
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.
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.
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 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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?
Maybe schedule a moving day and recruit some of your neighbors and friends to help.
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.
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.
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.
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.
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.
You might consider building a few windscreens in your rooftop garden, to cast some shade and protect tender plants.
Last but not least, consider how much your rooftop garden project will cost. Unfortunately, rooftop gardens are not inexpensive projects.
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.
The following list is not exclusive but does contain vegetables, herbs, and flowers that are particularly well-suited to rooftop gardens.
These sun-loving annuals are just perfect for an edible rooftop garden. Tomatoes love heat and can stand to get a little dry.
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!
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.
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.
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!
No rooftop garden is complete without at least a few flowering plants – a feast for our eyes and food for urban pollinators!
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.
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.
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.
Ornamental grasses happily spread to fill their container or bed, keeping barren soil from flying away.
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.
I hope you found this article helpful. If so, please share it with someone who can use the information.
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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.