Roof Garden Tips

Roof gardens continue to rise in popularity. They are installed most often in urban areas where planting space is limited. Green roofs keep buildings cooler in summer and warmer in winter. Rainfall is filtered through the plants before entering the sewer system. This process helps keep air and water clean. Residential gardeners also install roof gardens on their homes and out buildings.

Plan the Roof Garden

Before you start, determine which type of roof garden is suitable for your home or business. Intensive roof gardens have deeper soil pockets and can sustain full-sized trees and shrubs. This is usually more feasible for commercial buildings with flat concrete roofs. Semi-extensive roof gardens have a few inches of soil, so a wide variety of perennial plants can be installed there. The average roof can only support these two roof gardens if it has been properly prepared. The extensive roof garden has a very thin layer of soil or a rock and lime layer. This will support small plants with tiny root systems. The average roof can be converted to an extensive garden by adding the right barriers. Keep in mind that the roof will need to support the weight of the gardener, as well, for planting and maintenance.

Prepare the Space

Most of the time, a roof garden consultation and the preparation are done by a professional. Permits may be necessary in some areas. An expert can help you devise a plan, even if you want to install the roof garden yourself. The proper steps will depend on your climate and roof type. In a hot, dry region, moisture blankets are used to keep the plants from drying out. In wet regions, barriers will keep water from pooling on the roof. The right steps will protect your roof and help the garden grow successfully.

Maintain the Roof Garden

If the right plants are installed, normal rainfall may be enough for them to survive long term. Unless your structure is shaded by trees, or buildings in the afternoon, the roof will get very hot. Watering often may be necessary during the first year. If you plant to sow seeds, follow the directions on the package. Seeds cannot be allowed to dry out during the germination and seedling stages. Devise a plan for maneuvering around the plants without stepping on them. Leaving small bare patches is usually sufficient. The intensive and semi-intensive roof gardens are watered and maintained like any garden. The extensive roof garden is created to withstand the environment and take care of itself once established. The plants will fill in the stepping spaces later as they spread out.

Make Good Plant Choices

A commercial roof can hold an intensive roof garden. Containers can be heavy, but they are often the easiest choice for this type of garden. Consider how you will get the plants and soil to the roof. The sun exposure will allow for palm trees, fruits and vegetables. Semi-extensive roof gardens vary more, depending on whether the roof is flat or peaked. They may have several inches of soil, so choose plants with suitable root systems. Good choices might be perennial wildflowers, grasses or vines. The extensive roof garden may only have an inch of growing medium, more suited for moss, lichens and succulents. Roof garden blankets contain the growing medium and the plant seeds for use on extensive roof gardens. The best way to design your roof garden is to visit as many as possible, and see what presently works in your region.

Keywords: roof gardens, container gardens, perennial wildflowers, sedums and sempervivums, roof garden blankets

About this Author

Marci Degman has been a Landscape Designer and Horticulture writer for since 1997. She has an Associate of Applied Science in landscape technology and landscape design from Portland Community College. She writes a newspaper column for the Hillsboro Argus and radio tips for KUIK. Her teaching experience for Portland Community College has set the pace for her to write for GardenGuides.com.