Designing Raised Beds for your Garden
Building raised beds, alpine pavements and sink gardens offers the average gardener the greatest scope for growing alpine plants. A unique compromise between size and shape, they can fit into almost any garden space. The original number of constructions can be increased as the pocket and time allow. Do not be too ambitious to start with; a small project can be built up gradually over a period of time.
Extending the garden may particularly suit the young married couple with children – what better way of introducing youngsters to the delights of gardening than with the supervised construction and planting of their own sites? At the other end of the scale, raised beds offer the elderly the best opportunities for a degree of independence not often possible in other forms of gardening.
Almost any site, sloping or flat, in sun or shade or both, may be considered suitable for the construction of a raised bed.
Obviously those constructed from natural stone will look best, but any retaining materials can be used. Where the finances are limited (and plants are the main concern anyway) the clothing of other materials by alpine plants can be very effective and help to take away their possibly stark effect.
The easiest shape to maintain is a relatively narrow one, whose centre can be reached, without undue effort, from one or more sides at the basic ground level.
The basic requirements for preparing the site are the same as for the rock garden: the most important being goodand absence of perennial weeds. Other similarities will be mentioned later. The most important difference is that maintenance should be easy and you should not need to tread on the site after it is completed.
Materials to Make Raised Beds
Taking natural stone first: this material can be used (unlike in the rock garden) in any reasonable size. It is not advisable to mix the types of stone on any one site; better to build two small sites with different types of stone than one larger one mixing the two together. Have a look at well-laid dry-stone walls surrounding some farms for inspiration.
Stones come in a variety of sizes and shapes. Do not be misled by some public gardens where you may have seen large stones used all the time; this is done deliberately to allow for misuse by the public, who insist on kicking them to see if they are strong or who simply sit on them, which dislodges the stones, one at a time. And, mindful that children will climb anything that can be climbed – either for pleasure or to retrieve toys – large stones or other building materials, may be the answer.
Apart from stone, a wide variety of materials can be used to build a raised bed: railway sleepers; bricks, particularly weathered ones; concrete, which should never be pebble-dashed or treated with a surface material to take away its stark appearance (it will chip and fall off after a cold spell); artificial stone,
both formally and informally designed. Regardless of the material used, the basic rule of nobetween each layer applies, because rain and artificial watering would gradually wash the soil away, causing the materials to dislodge and destroy the structure.
Designing a Raised Bed
There are various designs to choose from, but like the rock garden, in all cases the width will depend on the height (varying from 15cm to 1 metre (6in to 3ft)) which is also relative to the length and, in turn, depends on whether the ground slopes or not. If you build a bed 1 metre (3 ft) high, getting up to tread on the site may not be practical, but with a long, low site, not more than 60cm (2 ft) high, you can put in stepping stones and thus reach the centre or back areas, according to whether the site is independent or backs 0n to a wall. No construction should back on to a house or other wall with damp courses.
The shape of a raised bed will obviously vary according to the space available; try to avoid squares if at all possible and choose from formal rectangles, L-shapes or long curves. The spaces surrounding any site can be grassed, paved or left as bare soil. Where grass borders the walls, it is advisable to lay maintenance and mowing easier. Use the same soil mixtures as for a rock garden: humus-based for shady sites, and gritty mixes for the sunny ones.slabs, using the same material as the raised bed, between the grass and the site, as this makes