Q. What plants should I use in a rooftop garden?

A. There are a number of things to consider when thinking about planting a rooftop garden. These considerations include cost of installation, maintenance, as well as the type of roof and load-bearing structure. Planting in containers may be a simple, economical alternative to a planting bed. Generally, rooftops are considered to be hostile environments, particularly due to wind and sun exposure. Characteristics of plants appropriate for rooftops include short habit, small leaves, sun and wind tolerance. Plants must also be cold hardy for our region and preferably drought tolerant.

Examples of perennial plants installed on the rooftop garden at the Daniel F. and Ada L. Rice Plant Conservation Science Center at the Chicago Botanic Garden include lesser catmint (Calamintha nepeta); harebell (Campanula rotundifolia); dianthus, specifically Dianthus gratianopolitanus 'Firewitch;' sedums (Sedum spurium 'John Creech') and (Sedum acre 'Aureum'). Each of these would be appropriate for rooftop beds or containers. Please be aware that containers require winter protection.There are many constraints and considerations involved in building a rooftop garden.