Rooftop gardening is quite challenging, but the idea is not new but has become very popular now with the city dwellers since they are able to utilise the precious place available for a green haven ..

History

When we go back into the history of terrace or roof top gardening, it is but natural that we think of Hanging gardens of Babylon which were built on mountain sides at different levels which is still considered an architectural and botanical marvel. Babylon is present day Iraq , although in the ancient times it was known as greater Persia. The hanging gardens of Babylon are one of the seven wonders of the world. Persians were known for their beautiful  gardens filled with trees, bushes, flowering creepers and trailers and water fountains and they constantly experimented trying  their hand at developing different kinds of parks and private gardens, palace gardens and some of them were also built within the courtyards, some of which were raised.

This style of gardening spread to Italy and Romans too grew some beautiful gardens on mountain slopes and in their palace courtyards. This later spread to England and other parts of the world. It must have paved the way to present day terrace gardens.

Advantages of having a terrace garden

There are many good reasons why one can plan to have a rooftop or terrace garden since the advantages are many.

Most importantly , a terrace garden helps in keeping the house cool which is an added advantage.While it also helps save money ( when you grow vegetables and fruits) , having a garden on the roof or the terrace keeps a person and the family busy and occupied in a healthy manner.

It also makes good use of a space that would otherwise have been vacant and makes the entire place look attractive. Rooftop gardening increases access to ones private outdoor green space.

You have much more green space to enjoy within the confines of your home. Most terrace gardens are secluded and provide an ideal spot for the family to relax and pursue their hobby. When you see those lush green roof tops in some houses you feel as if you are on an oasis. Rooftop gardens act as ecological oasis in the over crowded cities and help greatly in improving the air quality by reducing air pollution and dust.

More than anything they look very attractive and decorative creating a cool and comfortable outdoor private space for relaxation, which is more than enough reason to grow plants on your terrace and once you start taking an interest , there is no end to it.

Some points to consider

1, Strength of the terrace and the building structure – It is very important to make sure that the roof on which the garden is to be laid, is strong enough to carry the weight of the garden. A terrace garden requires soil and watering makes it wet and heavy .Wet soil can weigh more than eighty pounds per square foot and when you take that into consideration, that is a lot of weight being laid on the terrace and your roof must be able to support this weight. So it is better to consult a builder or a civil engineer who will be able to advise you about the feasibility of having a terrace garden.

2, Soil - Once the strength and other considerations have been met with you can go ahead with your plan of having a terrace garden. Spreading a layer of peat or moss will be helpful to ensure drainage instead of having a slushy soil that easily gets washed away while watering. Peat moss can also be used to ensure that there will be sufficient base soil.

3, Make it waterproof - One has to see that the roof is waterproof .To make sure that there will be no leakage and that your terrace is completely waterproof , it is better to consult an expert who will be able to guide you on how to go about it. This has to be done right at the beginning before spreading the soil.

4, Ideally,  the roof or the terrace should be slightly slope d and have an effective drainage system. Sloped roof is good since there will be no water stagnation which is what causes problems to the roof structure.

Choice of Plants

Once the garden is ready, with the soil laid out it is time to grow plants. Since there are certain limitation while planning a roof garden ,it is necessary to choose the plants with shallow root system which will not penetrate the roof floor in the long run. Growing plants that tend to have long and complicated root system might not be a good idea. But there are instances where, with careful planning people have grown fruit trees like Papaya, Guava and plantains on their terrace.

It is also advisable to grow such plants that flower at various periods of year so that you have some colorful blooms all through the year .Since the terrace is open to the sun most flowering plants tend to do well and flower profusely provide they are provided with enough water , compost and other nutrients.

The best bet is to have some trailing plants and which are not too heavy but are able to grow well anywhere as long as support is provided and they have space to spread. Many of them come with bunches of beautiful looking blooms, that look appealing on your terrace.

Some plants that are known to thrive and do well on the terrace or roof are Foliage plants like Asparagus, different varieties of colorful Coleus plants , any variety of Croton, diffenbachia, dracena, peperomias, philodendron rubber plant, etc.

And among the flowering plants, seasonal flowers like Anthurium, Asters, Balsam, Calendula, Celosia, Cosmos, Daisy, Dianthus, Gaillardia, Marigold Nasturtium, Pansies, Phlox, Verbena, Zeinia, etc., and perennial flowers like Carnation, Chrysanthemum, Dahlia, Rose, Tuberose all do well. Here what is to be noted is that most flowering plants do well provided they are planted in large pots in manure mixed soil.

Among the fruit trees that can be easily grown on the terrace, Gooseberry, strawberry, peach, pear, pineapple pomegranate are the most popular varieties.

 Cacti and succulents - Cacti and succulents do exceptionally well on rooftops since they receive enough sunlight . Most cactus plants need a reasonable amount of sunlight and this combined with a fair amount of water and other favorable conditions make them grow well on the terrace. So one can grow any variety of cactus on the roof top, even the trailing and flowering varieties. Some popular varieties that can be easily grown on the terrace are Agave, Aloe, Kalanchoe, Opuntia, Cehpalocereus, Notocactus , Nyctocereus, etc.

Vegetables too can be grown easily on the terrace. Tomatoes can be grown in polythene or discarded cement bags filled with garden soil mixed with compost and other vegetables like Brinjal ( Aubergines) , ladies fingers, green chilies, lettuce, spinach and mint grow well on the roof top since they are exposed to sunlight all the time. Curry leaves too grow lush and do well when grown in large pots.

Compost and the Soil Requirement

You have to take special care to provide fertile soil for the plants grown on the terrace. Since most of them would probably grown in pots and distributed across the terrace , a garden soil mix is good enough. But when you plan to have plant beds on the terrace – generally, a soil layer of 10-20 cm thickness is required for planting various foliage and flowering plants.

A good soil mixture for roof gardening must consist of garden soil, coarse sand , and well rotten farm yard manure or organic manure in the ratio of 2:1:1 for flowering plants but for foliage plants, a mixture containing equal part of soil and organic manure is the best. It is the same for vegetable and fruit plants as well since they require more nutrients.

If you are growing plants directly on the terrace, the soil needs to be changed or at least the top soil replaced every 3 years.It can be done one stretch at a time to make it easier for you. Remove all the plants and pots if they have been arranged on the soil bed and dig through the soil to loosen it. Take off the top soil to about 5 cms depth. Replace it with newly mixed garden soil as discussed in the previous paragraph. This ensures that your plants grow well and remain healthy.

Potting and Repotting

When you decide to grow plants in pots certain things need to be considered . Before potting, the container should be thoroughly washed and if possible sterilized to keep pests and insects away. Add a few pieces of tiles or pebbles to cover the drainage holes (some pots have more than one). A thin layer of coarse sand or a mixture of small stones and sand should be spread at the bottom of the pot.This helps in proper drainage of excess water without the soil getting washed away.

You can now add some of the potting soil which should ideally be a mixture of soil , sand and organic manure. Place the plant and add soil around it so that it settles in firmly. Press with your finger tips so that the soil remains firm but not too tight. Potting soil may be added to fill up the container leaving 2 -3 cm , so that there is no overflow of either soil or water. A light watering is required immediately after planting and keep the pot in the shade for a few days until the plant gets established in its new environment. Once the plant shows signs of growth you can place it on the terrace, wherever you want to keep it.

Re-potting on the other hand is an ongoing exercise that needs to be done every year when the pots are small and once every two years when the pots are large. The pot should be checked once in a year during monsoon season (June-September) just to make sure that water is being drained properly. However, repot the plants only after the rains recede. Generally repotting is required if the roots of the plant are found to cover the entire pot.

Repotting may also be required if any plant looks too large for its pot or the water passes through the pot too quickly which is a sure sign that there is not much soil left in the pot  and the plant is hardly getting any nutrients or even the basic needs .You can also repot the plant in the same pot with fresh garden soil and manure after trimming down the roots. It is always better to repot in a container that is one size larger than the previous one unless the plant has grown too big and needs a much larger pot.

Some of the well known terrace gardens across the world

Other than the world famous garden in Egypt, the nebuchadnezzar's hanging gardens of Babylon, we have one in our own country that is well known for its beauty. The Nishat garden of Kashmir which is also known as the garden of Delight is one of the largest Mughal Garden on Dal Lake. It was laid out by in the year 1632 A.D by the Mughal king Jahangir and his family. It has a magnificent view to the west and has a panoramic back drop of the Himalayan mountains in the East. The garden had originally 12 terraces on which the garden was laid out.

Another very impressive and beautiful terrace garden is fo.und in Israel. It is known as the Baha'i terrace gardens of Haifa, which is a holy city. The gardens are known as the hanging gardens of Haifa and built around the shrine of Bab on Mount Carmel. The gardens are stunning to look at and one of the most visited spots in Israel. It is relatively new since it was opened to the public only in 2001. 

Conclusions

With the ever shrinking green spaces in the cities both large and small, roof gardens or terrace gardens add a much needed touch a green and keep the environment relatively healthy. We are surrounded by buildings on all sides and to have some greenery on top of the building seems so refreshing. When more people take an interest in keeping their terraces green, they can hope to have a cooler home during summer months and also contribute to  the beautifying of  their city.


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