Monday, 6 June 2011

Gardening on a slope


Dundee town has grown around the Law Hill, Balgay Hill and even Menzieshill, so there is a fair bit of steep slopes incorporated into housing development land.
The challenge of a sloping garden will vary according to the degree of severity, the type of soil and whether the slope runs towards the house or away from it. Slopes can create a dry garden by allowing surface water to run off it, or a flooding problem if you are at the bottom of a hill. Problems of steep sloping gardens are usually left by the builders for the house owner to solve. However if the slope is severe and runs towards the house the builder is most likely to have tackled any potential drainage problem which could affect the property.  However it is always a wise move to check the property to see if there is any history of flooding or water damage.
For every negative aspect of a slope there is always the positive side. You may be blessed with a burn that can create a fantastic water feature garden. A rock garden  is perfect on a well drained slope. Many plants look better if viewed from below e.g. Fuchsias, Lilies, Himalayan blue Poppies, and some better if viewed from above e.g. Tulips.
The slope allows terrific scope for gardening creativity in both soft and hard landscaping so take time to consider all aspects before getting the spade out.


If your garden is at the bottom of a slope, surface water causing local flooding after heavy rainfall could be a problem. Wet soil may be indicated if you see a lot of moss, sedges or buttercups. It may be sufficient to cultivate deeply to allow water to percolate through the soil, but if the flooding risk is high consider some garden drainage. This could be a simple drainage system of perforated pipes under a gravel path leading to a decent sized soakaway. A more ambitious project may be necessary with professional advice needed on depth, type and size of perforated pipe, backfill material, extent of run and connection to an outlet. If using a surface water outlet the connections are critical and must be done properly incorporating a catchpit so that garden silt or debris can be filtered out in a sump to be cleaned out periodically.


After drainage, good access must be incorporated into the design to allow for weeding, planting, pruning and wandering around enjoying the garden. There must be plenty of flattish areas to work from connected by a path network. Strategically placed large bushes and trees can help to hold onto to assist stability. Footpaths on very steep slopes are best with a handrail for safety.
A path system may be formal with slabs, bricks, and breezeblocks, or it can be sympathetic to the landscape with natural wood risers backfilled with course wood chips. A trip to a builders merchants yard who specialises in hard landscaping can give many ideas to work on.

Retaining Walls and Terracing

Really steep banks may require retaining walls next to footpaths, but terracing with large rocks will give a more natural appearance. Good quality natural stone can often be acquired from builders yards if they have been doing any demolition of old buildings, or it may be purchased from a local quarry. The size of the job will determine whether it is done in house or whether a bricky or stone mason is employed. There are plenty of excellent dry stone wall builders who can create an attractive wall with strength. If cost is a factor breezeblocks can be used for speed and strength. Their formal appearance can be softened with ground cover plants allowed to trail over the edge.
Make sure any walls are strong enough to retain the bank for at least 50 years and provide weep holes for drainage.
Terracing is very useful to break the bank into a series of flat areas held up by as big rocks as you can find. During garden maintenance you will want to scramble over these rocks without fear of them toppling over, so size is important. A JCB may be needed to move big rocks around. Try to create a series of natural looking rock faces with the rocks relating to each other. Bury at least two thirds below ground. Create a series of plateaux  by cut and fill over the slope.


This can be an important option to create a flat patio adjacent to the house on a steep bank. Often there will be space left below the decking as the slope falls away. This is useful for storing garden tools or given over to the kids as a den to play in. Much safer than a tree house.
 Make sure your patio enjoys plenty of sunshine, some privacy and shelter from winds. Decking has been in fashion for a few years now, so there is plenty of information on materials, construction methods and maintenance of the wood. Make sure it is strong, the wood is well preserved and the design safe.

Plants for soil stabilisation

Once the slope has been hard landscaped, the planting can now be thought out. Terraced slopes and walls allow a fair bit of easy planting at waist height, so these areas can be more intensively gardened. Other areas of steep slope may be better with permanent planting, choosing plants that can hold the soil together to prevent any erosion.
I garden on several very steep banks with a fair degree of walls and terracing. Over time some plants prove much better than others in binding the soil surface together.
My favourites include Flag Iris, Delosperma, heathers, London Pride, Euonymous, variegated ivy, numerous dwarf spreading conifers, Shasta daisies, fuchsias, rhododendrons, azaleas and hostas.
For the larger garden use philadelphus, saskatoons, ceanothus, viburnums, kerria and cornus.
It always helps if bulbs can be interplanted as they can be very good at naturalizing. Bluebells and grape hyacinths are some of the best.


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