Roof top gardens are an environmentally friendly solution to improving air quality. The Science Buddies project estimates that sod roofing--the installation of a grass covered roof surface measuring about 4.9 feet in length and 4.9 feet in width--can produce as much oxygen as one human being breathes in one year. Roof top gardening is often the only option for the eco-friendly hobbyist when it comes to raising vegetables and flowers in urban settings. Roof top gardening ideas must address space limitations as well as climate considerations.
The easiest way to start roof top gardening involves the use of containers. Pick containers that are sufficiently tall to support the root growth of larger plants and arrange them in visually appealing patterns. Annuals and perennials both can thrive in containers that are no deeper than six inches; shrubs require depths of about 18 inches.
The downside of container gardening is the consistent need for watering, as container plants that are not protected from the sun' tend to dry out quickly. Temperature measurements taken from Chicago roof top gardens showed that during an average summer day with temperatures in the 90s, the roof gardens experienced temperatures of about 119 degrees Fahrenheit.
Choosing plants that can withstand heat and also drought is your best option. For annuals, consider ice plants, rose moss, cornflowers, sage, morning glories, zinnias and sunflowers. Wildflower mixes you can purchase at your local home improvement gardening store also provide good options for the roof top container gardens. In some cases, those plants are perennials.
You may want to consider setting up the roof to garden as a recreation area. If this kind of secondary roof use appeals to you, consider trellising as your primary gardening method. That allows you to take advantage of your containers but spreads the plant growth upward and maximizes usable roof space. For example, clumping bamboo grows quickly to provide an attractive privacy hedge, and daisy bush offers all year greenery, while grasses and annuals---such as Irish Molly--offer splashes of color during the spring and summer months.
Install a pergola or mount lattices and encourage potted grapevines and ivy to climb up those structures. Group pots with smaller plants around their bigger and more robust counterparts to receive shade and shelter from sun and wind.
Semi-Permanent Planting Beds
A more enduring method of roof top gardening is the construction of larger planter boxes. You need to first install a waterproof barrier that allows you to pile several inches of soil onto the roof. Surround it with wooden planks to keep the soil from spreading, and you may now use these semi-permanent planting beds to grow plants. Watering may be accomplished with soaker hoses. Annuals and perennials are once again good options. In addition, this is a workable setup for a productive vegetable and herb garden that includes even root vegetables.
Before installing large planting boxes, be sure to have your roof inspected to make sure it can handle the added weight of soil, water, and plants.