Moss' Top x 2 Roofdeck Plants

Selecting Rooftop Plants

When selecting plants for patios and balconies, consider those from habitats that most closely match your conditions, such as areas exposed to wind and sun, with limited water and soil, as well as large temperature fluctuations. Plants from areas like scrubland, screes, mountainsides, and deserts often make great rooftop, patio, and balcony plants.

A common thread among drought-tolerant plants is foliage that's hairy, waxy, hard, small, thin, and/or leathery. Deep taproots or extensive branching roots also help with drought resistance. Below are some examples of plants that can beat the heat!

See also:
Rooftop Gardening
Rooftop Gardening Dos and Don’ts
Ten Steps to a Happy Rooftop Container Garden

Top Ten Low to No Maintenance Rooftop Plants
If you are capable of some maintenance (mostly watering) then these are the some of most ornamental and productive plants for rooftops.  But if you have a brown-thumb or cannot water, skip to the "Low to No Maintenance" list.

•Regent Serviceberry (Amelanchier 'Regent')
• Ring of Fire Mini-rose (Rosa 'Ring of Fire')
• Basket-of-Gold (Aurinia saxatile)
• Asiatic Lily (Lilium cultivars)
• Columbine (Aqulegia cutlivars)
• Hyssop (Hyssopus officinalis)
• Goblin Flower (Gaillardia 'Frenzy')
• Ornamental Peppers (Capsicum annuum cultivars)
• Moss Rose (Portulaca grandiflora)
• Rain Lily (Zephyranthes species and cultivars)
 
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Top Ten Low to No Maintenance Roofdeck Plants 

These are the perfect plants for dry areas and parts of the country with watering restrictions. However, even these tough plants require adequate containers with well drained soil.  The size of the pot should match their root system.  For Hen&Chicks a small pot will do, but the Palo Verde tree will require a very large and deep container.
• Palo Verde (Cercidium) [frost tender]
• Agave (species and cultivars) [frost tender]
• Aloe (species and cultivars) [frost tender]
• Yucca (species and cultivars) 
• Red Yucca (Hesperaloe species and cultivars) [some frost tender]
• Upright sedum (Hylotelphinium cauticola and cultivars)
• Creeping sedum (Sedum album, middendorfii, kamschaticum, rupestre, acre, etc, and cultivars)
• Hen&Chicks (Sempervivum species and cultivars)
• Beard-of-Jove (Jovibarba species and cultivars)
• Tulip - Tulipa tarda has proven to be the hardiest, but other species and cultivars may work in areas not as cold as Chicago.  [requires a winter chilling period]

For a more complete list of low to no maintenance rooftop plants check out Some Like it Hot