A rooftop garden is a collection of container plants that home gardeners or landscapers keep on the rooftop of a flat building, often an apartment building. Plants can vary from vegetable plants to ornamental shrubs. The setup can be as simple as planting a few plants in terracotta pots or as established as constructed garden beds with automatic watering systems. Rooftop gardens share similarities with green roofs, or roofs planted with sedum and mosses to help with insulation and stormwater runoff

Types of Plants for Rooftop Gardens

Weather conditions of roofs can vary widely. Some roofs get full sun while neighboring buildings shade others; some roofs can reach temperatures up to 170 degrees Fahrenheit, while others experience high winds. When selecting plants for your rooftop container garden, consider the weather conditions of your roof and choose your plants accordingly. Here are a few types of plants that may thrive on your rooftop:

1. Drought-tolerant plants: Many rooftop gardens exposed to sunny and windy conditions require deep, consistent watering to help the plants thrive. If you don’t have the interest in or ability to install a drip system or rain barrel cistern, you may get tired of hauling a watering can to your roof to water the plants daily. Planting drought-tolerant plants can help make your rooftop garden low maintenance and easier to manage—consider plants like desert succulents like the snow rose, sage, butterfly weeds, and evergreen trees and shrubs.

2. Shade-tolerant plants: If neighboring buildings or trees shade your roof for much of the day, shade-tolerant plants are a great option. Some popular partial-sun plants include hostas and lettuces.

3. Sun-loving plants: Many roofs experience full sun (at least six hours of direct sunlight per day), so sun-loving plants are the most logical option. If your roof gets a lot of sun, consider full-sun plants like tomato plants and strawberries, small trees like Japanese maple trees, and flowers like marigolds, wildflowers, and coneflowers.

4. Wind-tolerant plants: Many roofs experience higher wind conditions than ground-level gardens because there aren’t other buildings or trees blocking the wind. If your roof gets a lot of wind, consider low-to-the-ground shrubs and groundcovers like ornamental grasses, hydrangeas, and honeysuckle bushes.

Advantages of a Rooftop Garden

Rooftop gardens have many advantages:

1. Great for limited spaces: One of the main advantages of a rooftop garden is that it allows people to keep outdoor plants at home regardless of their backyard situation. Rooftop gardens are a popular urban garden choice for people who live in apartments and condos.

2. Higher chances for sunlight: Rooftop gardens are more likely to receive full sun than on-the-ground gardens or houseplants since they are typically not shaded by trees or other buildings. This ample sunlight allows gardeners to select from a wider range of plants, including vegetable plants and sun-loving flowers.

3. Pest-resistant: Many on-the-ground gardens can be targets for weeds and local wildlife like deer and rabbits, making growing certain plants difficult. Rooftop gardens grow plants out of reach of those animals and many weeds, limiting the kinds of pests that can affect their growth and reducing the need for weeding.

4. Visual appeal: Rooftop gardens are a great way to add visual interest to roof space, turning a flat area into a more pleasant outdoor space with greenery for relaxing or entertaining. You can also add decking, a fire pit, a pergola, or decorative chairs to further beautify your rooftop garden design.

Disadvantages of a Rooftop Garden

Rooftop gardens also have a few disadvantages:

1. Water difficulties: The biggest disadvantage of rooftop gardening is creating a sustainable watering system. Rooftop gardens are typically extra thirsty (due to high sun and winds) but are more difficult to water than other gardens because they’re farther from spigots and water lines and require a little more engineering to set up drip irrigation systems or a cistern.

2. Adverse weather conditions: Rooftop gardens face more inclement weather conditions than other gardens, especially high winds, and hot temperatures, so it’s important to get especially hardy plants for roofs that regularly experience adverse weather.

3. Limited to containers: Rooftop gardens need to be in containers or raised garden beds since they’re up off the ground, which can limit the variety of plants gardeners can use. Container gardens can come at a higher cost than planting straight into the ground.

4. Weight restrictions: Roofs can only handle a limited amount of extra weight. When planning a rooftop garden, you’ll want to ensure that your roof can handle the weight of the containers, soil, and water cistern, if you plan to install one.

How to Start a Rooftop Garden

Here’s a basic step-by-step guide to starting a rooftop garden:

1. Check your building codes. Before you buy any plants, check with your local building codes to ensure that you’re allowed to plant on the roof. If you’re in an apartment or condo, check with the building owners or condo association to see if they’ll permit plants in the shared space. If you’re in a house, check with the homeowners’ association or look into local building codes to see if there are any restrictions on height or aesthetics.

2. Select your plants. When selecting plants for your rooftop garden, consider the weather conditions of your roof and choose your plants accordingly. If your roof is in full sun or painted black, choose sun- and heat-loving plants; if your roof has few wind blocks, choose low-to-the-ground plants and use bottom-heavy planters.

3. Choose or build containers. Rooftop gardens are endlessly customizable—for planters, you can plant in simple five-gallon buckets (with drainage holes), or DIY custom-raised beds for a more polished look. Whatever you choose to plant in, make sure the container has adequate drainage to avoid your plants’ roots sitting in water or soggy soil, which can lead to root rot. Consider the weight limits of the roof as plastic or wooden containers will be lighter than concrete or stone.

4. Set up wind blocks. If your area gets lots of wind, you may want to set up windbreaks around your plants to prevent them from getting blown over on your roof. A trellis or a perimeter wall will help block heavy gusts and anchor your plants in the soil.

5. Prepare the soil. Since rooftop gardens have no access to ground soil, you’ll need to purchase soil and bring it up to your rooftop containers. Most plants thrive in well-draining soil rich in organic matter, like potting soil amended with organic compost.

Plant your selections. Once you prepare your containers, dig holes in your containers and plant your chosen plants. Water thoroughly afterward to settle the soil and anchor the plants.

Water the plants as necessary. The simplest way to water a rooftop garden is with a watering can. However, for larger rooftop gardens or to avoid climbing the stairs every morning with a watering can, you can set up more extensive watering systems. A popular option is setting up a rain barrel or cistern to catch rainwater in a watering can. You can also set up a drip system connected to a roof-level water spigot.