Stone raised beds have an almost unlimited lifespan. You can use all kinds of stones for this, although natural stones are often very expensive. A cheaper alternative are concrete blocks, which no longer have to look artificial.
Cement blocks are just one variant of the concrete raised bed
Concrete blocks allow great variety
Concrete is not only an inexpensive, but also a very versatile material. You can use exposed concrete to build a raised bed and perhaps create an interesting contrast to the naturally designed garden. However, there is also a whole series of concrete blocks that are externally modeled on natural stones. With their roughly hewn visible side, the broken edges and different colors in a natural look, such stones also look very pleasing in the natural garden.
Dry stone and mortared walls
Another advantage of concrete - in addition to its price and variety - is its significantly lower weight compared to natural stones. This comes into play when building walls, for example, if a raised bed is to be built on a slope. For high natural stone walls you need very large and heavy stones for static reasons alone. Accordingly, the edges of the bed are very thick, so that there is hardly any bed space left. You can also build both dry and mortared walls from concrete blocks, with mortar walls in particular being placed on a frost-free concrete foundation. The heavier the construction, the deeper and stronger the foundation has to be built. In addition, an inner foil is always recommended for mortared walls, so that the mortar joints do not become porous and therefore flexible due to the constant effect of moisture.
System blocks made of concrete / lightweight construction systems
So-called system bricks are easier to install, as they practically hook into each other thanks to grooves, resulting in stable walls. Since these are hollow blocks, you can even build very high walls thanks to their low dead weight. To make the hollow bricks heavier and therefore more stable against the internal pressure, you can also fill them with gravel, grit (€46.95) or sand. The manufacturers always give instructions as to the wall height from which a mortar foundation or special adhesive between the stones must be used. If in doubt, ask a specialist for static calculations. If you want to build curved raised beds, you can use concrete blocks with a conical shape. These make it easy to build curves. As with dry stone walls, you can occasionally build wider joints here so that they can be planted or used as a shelter for small animals.
Inexpensive manhole rings
Sections of manholes made of precast concrete can also be used as raised beds and have a practically unlimited lifespan. In addition, such raised beds can be set up quickly and easily - you only need to transport one or more manhole rings of the right size to the desired location, fill them and plant them. However, you will need a machine - such as a small excavator - to transport them, as they are very heavy and cumbersome. Smaller rings can also be rolled into place by hand if you let them unload vertically. Manhole rings are available from builders' merchants in many different sizes and with different diameters, although only rings up to approx. 150 centimeters are practical - up to this size you can just about reach the middle of the bed. Shaft rings can be placed on top of each other in the groove system so that you can build the raised bed at the desired height. Since they are waterproof, you also do not need a film.
tips
Concrete slabs can also make a stable raised bed wall. For example, you can simply place high paving slabs made of concrete upright in a bed of dry mortar - the raised bed is ready. Concrete palisades can be buried upright in the ground and thus form a stable bed frame.