Rooftops are usually where you put extra or unused furnishings to make more room for your living or bedroom spaces. But they are actually ideal for gardens--because they're open areas that get more sunlight, air, and dew.
And you may even make use of the extra or unused furnishings for your gardens. Old sofas are often made of wood you can re-use to build earthen pot platforms of pedestals.
This rooftop garden on the left made use of old window grills and mesh wire fences to enclose spaces and provide structures for vines to crawl on.
This vegetable plant on the left is upo (some say the English term for it is "sitting vegetable. Amusing.). The upo fruit is rich in fiber and vitamins and minerals.
Another ideal vegetable crop to grow on the rooftop is okra because it needs enough sunlight. Youcan simply use large empty tin or plastic cans filled with good soil to plant them in. My friend used discarded water buckets to plant okras, cabbages and tomatoes.
He added that he even planted a moringa tree in a larger water bucket, and it seems to be working. He also plants smaller vegetables like onion spring in smaller plastic containers derived from cut plastic bottles.
The important thing is to make sure the containers hold enough soil and that the soil is replaced every month with new soil revitalized through composting, which he also does on his rooftop.
Rooftop gardens make gardening possible even in crowded places in the city. In fact, it gives a challenging twist to gardening because you have to make your imagination really work.