With the terrace being fairly sheltered, getting some sun and immediately outside the kitchen, both the client and I were interested in a three-dimensional composition that will give a lush view. We matched the white of the walls with smooth raised beds and iroko hardwood coping to match the deck. An evergreen collection of exotic looking plants follows the layout of the raised beds giving a strong architectural elevation.
Here I was able to use some of my favourite architectural plants. They had to be combined so that textures contrast as well as heights and colour. I would not usually use bamboo on roof terraces as too much wind and it will not perform well and may end up looking unsightly and suffer. Yet here with the high walls of Butlers Wharf the space had more of a courtyard sheltered feel. Black bamboo gives height surrounded by Phormium, Fatsia, European palms, ferns and grasses. A hardy, ornamental Banana provides a lush tall statement in the right border underplanted with variegated Hosta.
Viewed from the upper roof terrace the space feels more like a sunken garden than a courtyard and you may forget for a minute that you are at the top of Butlers Wharf. Gardening in raised beds has many advantages and with excellent drainage and timed irrigation the plant performance is optimised.
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Always consider access as it may not be possible to get long items into the site such as wood and tall plants. The lift should always be checked for size and all openings en route to the roof terrace measured for width and height. Larger planters are preferable on roof terraces as they are well balanced and the compost tends to retain moisture for longer.
Where the look might call for taller or narrower planters it is advisable to use an anti-topple device at the back of the planter and secure to it to a wall or the handrail of the roof terrace. Drainage for planters and containers tends to get overlooked and this means that calcium from the water gathers on surfaces tarnishing their appearance. It is far more preferable to have drainage outlets at the bottom of the rear elevation of the planter rather than the base. This way water excess can be diverted elsewhere on the terrace.
Many roof terraces will be exposed to high winds. Plants should be selected for their tolerance of wind – plants with small leaves tend to cope better with wind and grey leaved plants tend to cope better with hot sun. Automatic irrigation not only eradicates the need for manual watering and saves a great deal of water but is paramount in sustaining plants on roof terraces. The right programming for the different seasons promotes good performance in plant growth and should be customised for the varying conditions of each unique roof terrace design.