ROOF GARDENING : A MODERN ART OF BEAUTIFICATION

Short Communication

ROOF GARDENING : A MODERN ART OF BEAUTIFICATION

Ramesh Kumar

ICAR Research Complex for Neh Region, Sikkim Centre, Tadong 737 102, Gangtok-Sikkim

A garden always provides a space to relax but the limitation of space in big cities and towns has already set the door for enjoying the beauty at home. It is therefore, the need of the hour to earmark some area on the roof top for raising various plants so as to bring the real magic of nature to your home with some previous planning and thoughts.

Planning of roof garden

A roof garden is not a botanical garden and can be planned in the same way as that of kitchen garden. However, before planning a roof garden one should have the idea about the bearing capacity of the roof and drainage facilities as well to avoid any seepage in future. In order to create a pleasant garden, first one has to create a mental picture of his requirement. The kind and number of plants should be limited. Utility crops such as vegetables and one or two blossoming fruit plants may have to be accommodated in the plan. The rest area should be left for ornamental plants. An edible shrub is equally useful as it attracts a variety of birds that make the garden a more interesting place.

The view of the garden from the ground floor is very important and there should be something pleasant and colourful to look at from ground level as it gives the visitors their first impression of the way the family lives. Therefore, proper arrangement of the pot grown plant is essential to make them more attractive. Arranging the pot grown plants in a single row by maintaining their height on the outer most wall gives a fantastic look whereas mass effect on roof floor in triangular or round form keeping red in the middle, yellow and pink on either side gives a very contrasting and eye catching look to the spectators.

Selection of roof site and container

A roof garden is an outdoor refreshing place and must be viewed and enjoyed from more than one side. Shaded area, if any, can be used as a utility area such as work area and sitting place while the open space may be used for planting. A flowering plant should never be kept in the shade for a long period while a shady location should always be selected for foliage and delicate plant.

Various types of pot and container can be used for growing plants at roof tops. Usually earthen pots are the best and if the weight bearing capacity of the roof is less, it is better to use plastic or fibre-glass container. Empty tins and flower boxes can also be used but care should be taken that these must have a drainage hole, otherwise the plant may suffer from poor drainage. With regard to pot size, it will depend upon the growth habit of the plant. Use slightly bigger container for dwarf trees and shrubs while other plants can do well in medium to small sized pots.

Choice of plants

A wide variety of plants can be used for growing on roof tops but it is necessary to choose the plants with shallow root system which will not penetrate the roof floor in long run. At the same time, it is also advisable to grow such plants that flower at various periods of year and are very easily be maintained at roof top. Delicate plants must be avoided for this purpose. The following plants are well suited for such type of gardening:

Foliage plants: Asparagus, coleus, croton, diffenbachia, dracena, paperomias, philodendron rubber plant, etc.

Flowering plants: Seasonal flowers like antirrhinum, aster, balsam, calendula, celosia, cosmos, daisy, dianthus, gaillardia, marigold nasturtium, pansy, phlox, verbena, zinnia, etc., and perennial flowers like carnation, chrysanthemum, dahlia, rose, tuberose, etc.

Shrubs: Acalypha, bougainvillea, camellia, china rose, geranium, jasmine lantana, etc.

Trees: Ashoka tree, bottle brush, chrismis tree, silk cotton tree, etc.

Climbers: Antigonon, begnonia, gloriosa, ipomea and passiflora, etc.

Cactii and succulents: Agave, aloe, kalanchoe, opuntia, cehpalocereus, notocactus nyctocereus, etc.

Fruits: Gooseberry, strawberry, peach, pear, pineapple pomegranate, etc.

Vegetables: Bringal, broccoli, chillies, lettuce, tomoto, etc.

Soil

Generally a soil layer of 10-20 cm thickness is sufficient for planting various foliage and flowering plants. A good soil mixture for roof gardening must consist of soil, sand and well rotten FYM in 2:1:1 ratio for flowering plants but for foliage plants, a mixture containing equal part of soil and organic manure is the best.

Potting

Before potting, the container should be thoroughly washed and sterilized with 5% formalin solution. A small piece of curved pebble should be placed over the drainage hole to prevent its blocking. For proper growth and drainage, the coarse sand should be placed at the bottom over which a mixture of soil and organic manure may be added to fill up the container leaving 2.0-3.0 cm pot brim for irrigation. Planting is to be done by making a hole in the center so that any injury to young plant or its roots may be avoided. While planting, the soil around the plant is pressed to hold it firmly in the growing medium. A light watering is required immediately after planting and should be done with the help of rose cane. After that the plants are kept in the shade for about a fortnight before being placed at their actual location on the roof.

Repotting

The pot should be checked once in a year during monsoon season (June-July) and repotting is required if the roots of the plant are found to bound 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. Repotting is done either in bigger pot or in the same pot with fresh garden soil and manure after light root pruning.

Final touches

The secret of a successful garden mainly lies in the harmony of the surrounding. Therefore, some special features like greenhouse, lily pools, rockery etc. may be added later but these garden features must be in mini-form. For a greenhouse, use aluminum pipes for longer duration and bamboo poles for shorter duration. In such greenhouses, floor surface can be used for container plants; the walks for climbing plants and the air space for the plants in hanging basket. A rock garden should not exceed 0.5-1.0 m height while a lily pool must be painted with a light blue colour inside and any contrast colour outside. In order to minimize weight load on the roof, these garden features may be constructed with asbestos, fibre-glass, plastic or aluminum sheets. Aluminum sheets are comparatively cheaper and can easily be molded according to the desired shape of these features. These are then placed inside the soil on the roof surface to bring harmony to your garden.

Aftercare

The plants grown at roof tops require various cultural operations for effective management of the garden. Among these, pinching of 2.0-2.5 cm shoot tips is a regular practice to make the plants become bushy. In shrubs and fruit trees, pruning is required to check excessive growth once in a year after their flowering. Likewise, training is essential to give a definite shape to the plant while stacking is a must in climbers to keep them upright. Regular weeding of plants is very essential to keep the garden free from pests and diseases. During summer and rainy season the plants should be protected from strong wind and scorching sun as the roofs are always exposed to these conditions. The protection against such extreme conditions can be provided by putting a screen or an overhead pergola structure made up of bamboo sticks which can last 3-4 years. For permanent structure, one can use wrought iron or aluminum but the cost will be high.

Apart from this, watering has a direct impact on the over all performance of the roof garden as most of the plants may die due to inadequate or over-watering. The water requirement of the plant increases during its flowering stage and the frequency will be much higher if it flowers during summer season. Cactii and succulents require less frequent watering as compared to all other plants. Keeping this in view, watering is done when the soil just starts drying but always before it is completely dried up. In order to conserve the moisture when a person is away from his house for few days or so, it will be an excellent idea to put one end of a saturated rope piece near the plant and other end in a bucket containing water. The same can also be achieved by wrapping the pot and the plant in a polyethylene sheet.

Roof gardening in the Himalayan region of India is at its take off stage but the extreme of weather in the rest part of India hampers the growth and development of house plants. Therefore, it will be useful if the technology for the successful growing of house plants at roof tops is standardised to enable more people all over the country to enjoy the beauty.

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ENVIS Bulletin : Himalayan Ecology 11(1), 2003

G. B. Pant Institute of Himalayan Environment and Development

(An autonomous Institute of Ministry of Environment and Forests, Government of India)

Kosi-Katarmal, Almora - 263 643, Uttaranchal, India