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Sparkling Oasis

Take palms, tree ferns and other exotics, and just add water. Landscaper Paul shows how it's done.
Paul Newman, Oasis Garden Services, 16 Alexandra Road, St. Albans, Herts
Chamaerops No. 16, published online 23-08-2002

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Sparkling Oasis in 4 views.
Top left: General view of the garden, ready for turfing.
Top right: Construction-of the pools and cascade using 60 tonnes of stone & rock.
Below left: Oasis in the frost; the finished garden has its ftrst taste of winter.
Below right: The finished effect; cascade & top pool.

I am a landscape gardener and specialize in exotic, 'sub-tropical' and Oriental style gardens. One of my projects last summer was the planning and construction of a large 'sub-tropical' water garden.

A plan was drawn up, involving three pools, and the main feature is a dramatic waterfall crashing into a sparkling, cobble-filled pool. This then cascades over a series of weirs into a larger, lower pool. To give you an idea of size, the approximate dimensions are; header pool 1.5 X 1.5m (5ft X 5ft); middle pool 5 X 4.5m (16ft X 14ft); lower pool 8 X 7.5m (26ft X 24ft). As you can imagine, this involved a vast amount of rockwork for the construction of the waterfall, and to compliment the pools, some 60 tonnes m fact! This was weathered York stone hand-picked from a quarry in Lancashire. Some individual pieces weighed over a tonne.

The site was marked out and a large retaining wall was constructed against which to position the header pool and to form the basic structure for the waterfall. Rocks were then selected with matching colour and strata layers so as to form natural-looking rocky outcrops. Many pieces could not be lifted by hand and had to be hoisted into position using a homemade A-frame, with block and tackle. Even this proved insufficient for the largest rocks and an excavator was brought in for the biggest. This was also used to dig out the two pools to roughly the required dimensions, after which they were completed by hand.

As the clients intention was to keep Koi carp, a large and complicated biological filtration system was also built. It consists of a series of chambers through which the water is drawn, via the bottom pool, into a vortex. This spins the water, and any sediment and waste is drawn to the bottom, and can then be flushed through a bottom drain. The water is then forced through a chamber containing a number of suspended brushes. This acts as a settlement chamber and traps large particles. The water next weirs over two further chambers containing filter matting, where bacteria breed and colonize. It is these bacteria, which clean and detoxify the water by breaking down the waste and ammonia levels produced by the large fish. The final chamber is filled with 3/4" gravel and filters fine particles. The whole system is powered by a one horsepower ITT Marlon pump. To prevent algae and to keep the water clear, two ultra-violet light units were installed. The UV rays produced by the lights kill off the bacteria as the water passes around the protective tubes. The entire system is below ground level, and wooden hatches are fitted to enable access to the chambers and pump for maintenance. These are in turn hidden by wooden decking, which forms a seating area.

Once the pools were dug out and levelled, they were lined with 2" of sand and a Geotex underlay which cushions the thick Butyl liner against the very heavy rocks which were later positioned in the pools and on the shelf around the perimeter. As well as the 60 tonnes of York stone that surround the pools and waterfall area, four tonnes of Scottish beach cobbles were used to create a wide, sloping beach, leading into the lower pool. These have a wonderful colour when wet and will be visible under the water, kept clear with the filtration system. A bog garden was added to one side of the lower pool, and planted up with large, lush foliage plants including Ligularias, Lysichiton americanum, Peltiphyllum, etc., not forgetting the obligatory and monstrous Gunnera manicata which will overhang the water's edge, casting mysterious shadows in the dappled light.

After much backache from lifting heavy rocks and some final adjustments to the waterfall - the focal point - we could begin the planting. All the plants were chosen for their strong, architectural shapes and large, lush foliage to give a really exotic effect. Palms include 6 Trachycarpus fortunei - two at lOft and the rest about 5ft, 4 bushy Chamaerops humilis and a superb Butia capitata which was already beginning to form a thick, heavy trunk. Three of the Trachy's are planted in a group and look stunning as their crowns are at different heights. The other tall one stands on its own and looks wonderful together with its reflection in the pond's surface. The two remaining Trachys are planted either side of a winding pathway that runs around the back of the bog garden to the sitting area on the decking covering the filter chambers.

As the path snakes its way around, a jungley effect has been created by planting a grove of Phyllostachys aurea. The clumps of this bamboo are up to l5ft in height, and possess some wonderfully knobbly canes. Arundo donax (Spanish Reed) together with its variegated form add to the general effect. The sitting area referred to above has been made into a 'secret' place by the use of Phyllostachys nigra, the Black Bamboo, whose impressive, shiny, ebony canes (or culms) help to create the mysterious, jungley effect. On the left hand side of the waterfall Fatsia japonica and the large evergreen ferns Blechnum chilense, Polystichum setiferum, and the bright green Asplenium scolopendrium are planted in gaps and crevices between the rocks. The centrepiece here is a beautiful Dicksonia antarctica tree fern, with its graceful, spreading fronds arching out over the pool. The spray and mist from the waterfall keep its foliage and trunk moist, and provide the humidity that this plant loves.

The right hand side of the waterfall is planted with Sasa palmata. This is one of the best tropical-looking bamboos, as it possesses large, palm-like leaves up to 16" long and 4" wide. In front of the group of three Trachys a huge, jagged, wedge-shaped piece of rock has been half buried and looks as though it has exploded out of the ground. Here a group planting of Phormium tenax purpureum and the dwarf variegated bamboo Pleioblastus variegata. The Butia capitata is planted by the cascade section leading to the lower pool, along with Chamaerops humilis the two different leaf shapes and colours making a wonderful contrast.

Continuing further around the edge of the pool the path splits into two directions, one way leading back towards the house around an island bed containing more Chamaerops humilis and Cordyline australis. In the other direction, the path continues towards the lower beach area where the cobbles extend out of the water. Here a raised area has been created and planted with Agave americana and Yucca recurva. The Agaves will need protection only in the coldest weather and I am confident that they will do well as they are planted in extremely well drained sandy soil and receive full sun all day.

To the left of this area, a large bed has been created and planted with various Phormiums together with Eucalyptus niphophila, the Alpine Snow Gum. This attractive tree is one of the best Eucalypts for bark pattern and colour. As the tree grows, the bark stretches and cracks or splits to reveal the new inner bark, a marbled pattern combining grey, green and cream. The young stems and branches are bright red and glossy and form a beautiful contrast with the glaucous leaves and the colourful bark pattern.

Also here is Melianthus major. This large South African plant forms large, serrated, deeply cut leaves, and is a must for foliage lovers. This area will also be used to plant out the more tender exotics including the beautiful Cannas with their lush, banana-like foliage and exotic flower spikes. The purple forms are very attractive as are the wine-red leaves of Ricinus communis, the true Castor Oil plant. The variety 'Gibsonii' is the best and is an annual, easily grown from seed. The largest and perhaps the most stunning tender exotic has to be the Abyssinian Banana, Musa ensete. This huge plant can reach 18ft (5.5m) in height with leaves up to 12ft in length in a surprisingly short time and would surely be the pride of anyone's garden. Sadly it is not frost hardy and must be protected in winter. This is best done by lifting it in autumn and overwatering it in greenhouse or conservatory. The Japanese banana, Musa basjoo, may be grown all year round in sheltered gardens. Even when cut to the ground by frost, it will shoot again the following season and is very vigorous.

All the plants mentioned are surprisingly easy to look after and require the minimum of maintenance and care and will reward you year after year with superb displays of exotic foliage and colours.

After planting, the next job was the construction of the pathways and lawn area. A winding pathway leads from the patio and runs around the perimeter of the water garden, and thence to the lower lawn. This was edged with 'log roll' edging and haunched with a render mix to keep it firm and level. A layer of compacted hoggin was added to act as a sub-base. This was topped with 3" of grey/green stone chippings and makes a good contrast to the weathered York stone rocks. Sections of log were laid along the path to form a stepping stone effect. The two main lawn areas were rotavated, dug over and raked to a fine tilth to enable the fine quality turf to be laid. A smaller lawn area behind the grove of Bamboo and Phormiums creates a mysterious 'hide-out' and also has the best view-point in the garden as the waterfall can be seen from a distance, sparkling as it catches the sunlight between the arching canes of Phyllostachys nigra.

Specimen trees are to be planted in the lawn areas and include Pinus pinea, the Italian Stone Pine, Paulownia tomentosa which, if pollarded every year will produce huge, soft, velvety, yellow leaves, and Cercidiphyllum japonicum. These, together with various Acers will be planted for their brilliant displays of autumn foliage, to complete the scene.

Though of course it will take a while to achieve maturity, even the early effect of the garden is one of a lush, tropical oasis. I hope this article will serve to inspire all palm fanatics, and will give an idea of the wonderful effect that the combination of palms, other 'exotic' plants, together with water can achieve, irrespective of the size of the garden.

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