• Rooftops can be used as one of the best ways to maximize space in urban settings for creating gardens. Regardless of whether the building is a two-story structure or a seven-story building, rooftop gardens are easy to create and maintain with the use of containers and boxes. There is a large variety of plants that can easily be grown on rooftop gardens including dwarf fruit trees. The major consideration in creating rooftop gardens is the strength of the roof, because it has to bear the weight of soil-filled containers and pots.
  
  

Shrubs

• There are many sun loving shrubs that can be used effectively in rooftop gardens. Shrubs are multistemmed, evergreen or deciduous, flowering or nonflowering plants that can grow several feet in height. Since large trees are not an option in rooftop gardens, the larger shrubs can be used instead to create backdrops for smaller plants. Some sun loving shrubs of average height which can be used effectively on rooftops include bayberry (Myrica pensylvanica), cotoneaster (Cotoneaster divaricatus), firethorn (Pyracantha coccinea), flowering quince (Chaenomeles speciosa) and summer sweet (Clethra alnifolia).
  
  

Vegetables

• A number of vegetables that grow well in containers can easily be grown in rooftop gardens. These include radishes, carrots, strawberries, onions, potatoes, cabbage, red beets, cauliflower, collard greens and peppers. The growing conditions are different in rooftop gardens and tend to be a little on the extreme end. For instance, there is a need for a lot of mulch since water dries up very rapidly given the high winds and open sun. The soil used in rooftop gardening also requires a higher level of fertilization. Heat loving vegetables like tomatoes also thrive in rooftop gardens under proper growing conditions.
  
  

Flowers

• Using flowers on rooftops brings an abundance of color to the garden and creates infinite interest. A wide range of sun loving annuals and perennials can be chosen for rooftop gardens. Flowers are an essential component of rooftop gardens as they help to provide nectar for butterflies, bees and hummingbirds. These birds and insects have a hard time finding food in urban settings. The nectar of the flowers supports pollination of fruits and invites visits from dragonflies, mosquito-catching spiders and robins. Some good perennials that thrive in six to eight hours of direct sun include black eyed Susan (Rudbeckia fulgida), purple coneflowers (Echinacea purpurea), stonecrop (Sedum "Autumn Joy"), Shasta daisy (Leucanthemum superbum) and peony (Paeonia sp.).