With summer finally here, the cool breezes and open views of rooftops and balconies offer enticing alternatives to stuffy apartments. Add plants, and the shimmering mirage solidifies as a real oasis. Your efforts join a long lineage of green thumbed New Yorkers.
During New York’s Gilded Age, tenement residents grew crops in containers atop their apartments. Gardens sprouted above multiple theaters and restaurant venues including the Olympia Theater in Times Square and the original Madison Square Gardens, as well as the hotels Astor, Astonia, Waldorf, and Astoria. Rockefeller Center’s four acres of green space on its terraces are nearly a century old. And where better to build a contemporary rooftop garden than in Greenpoint, abundant with plant stores and aspirational gardeners and horticulturists.
For most beginners, a container garden is the place to start. If you have legal access to your building’s rooftop and the structural capacity of the site allows for a garden, great – you are ready to get growing. (Not sure? Visit the New York City Department of Buildings’ website to learn more about rooftop use for gardens, greenhouses and green roofs, the latter two may need professional installation).
Good to go? Greenpoint, it’s time to put on your gardening gloves and consider the following:
How will I use this space? Before you splurge on containers, soil and plants, consider your overall design. Mapping out your site beforehand is a smart way to avoid budget shortfalls. Include information that will help your plants grow, such as the cardinal directions (southern exposure gives your plants the most sunlight). If your objective is recreation, take notes or photos on what you love about New York City’s beautiful public green spaces, from Kingsland Wildflowers to the High Line. What plants, containers, shapes and colors mirror that effort?
Do I have access to water? Rooftops and balconies run dry (and windy) and a container gardening system exacerbates that desiccation. Are you gone for long periods of the day during the hot, dry weeks of July? Consider installing a drip irrigation system with a timer.
What is the microclimate of my site? New York City is growing zone 7b, but microclimate is unique to your site. For example, your rooftop or balcony may have more or less wind or sunlight than your neighbors down the block. If your rooftop has areas of ponding (water retention), shadowcast (e.g. light blocked by a water tower or an HVAC system) or other microclimate issues, this can help inform your plant selection. For example, growing vegetables in containers along the parapet edge of your rooftop is best for weight bearing capacity, but if the parapet blocks early April morning sunlight, any overnight frost or dew will melt away more slowly in that shadow than elsewhere on the rooftop. Sometimes the best way to learn about your microclimate is to get started – and move things around as you take note of your failures!
What is my budget? Prioritize high quality potting mix. As a lightweight growing media, potting mix is usually better for rooftops than pure compost or topsoil. For vegetables, an amended potting mix, such as Fox Farm’s, will give them the nutrients they need.
Next on the list are quality containers. It is your first year growing, you may want to start small with a few containers, and build out as your successes become apparent. Select containers that provide good drainage. This is healthier for your plants (waterlogging causes anaerobic soil conditions, acidifying and stinky) as well as alleviates the extra water weight on your roof or terrace. Do not damage the roof membrane. Standard membrane rooftops can get soft and sticky in the summer heat; do what you can to distribute the weight of the container so that it does not cause any subtle fissures. If you rooftop is not already protected, adding raised decking or an additional layer of waterproofing membrane can help. Finally, if you can lift up your container, so can the winter wind.
Once the growing season winds down, make sure you have a safe way to keep your dry, empty containers from falling onto unsuspecting neighbors below. If your budget is tight (or your sense of adventure is high!), one of the best ways to save money is to start your own plants from seed rather than transplants. A package of 250 seeds can cost as little as three dollars – less than the price of a single transplant!
In addition to the personal pleasure of living alongside plants , gardening offers innumerable ecological benefits. More green space means more food and habitat for the non-human creatures we share our city with, and cooler, cleaner air.
Most vitally, in a landscape of impermeable surfaces, every additional square foot of soil and plants captures storm water runoff. New York City has 540 miles of coastline and aquatic ecosystems from wetlands to estuaries, with water both salty and fresh.
On a tour of the Newtown Creek Wastewater Treatment Plant, I was advised that the best way to protect our marine environment is avoid using water flushing the toilet, running the dishwasher or showering during heavy rain events, to avoid adding to the volume of water running through our combined sewage overflow system. To this small ask, I would add tend a garden. Every New York City building stamps out the capacity of the underlying soil to absorb water. Every surface re-greened, whether ground level or six stories up in the air, benefits you and your neighbors for years to come.
To learn more about the brass tacks of rooftop gardening, read The Rooftop Growing Guide: How to Transform Your Roof into a Garden or Farm (Ten Speed Press, 2016). Annie teaches rooftop, vegetable, container, and sustainability-focused gardening classes for the New York Botanical Garden and with Atlas Obscura.