Most raised beds are made of wood, but there are a number of much more durable materials. In addition to the stone that is also used, various metals are also recommended for the border of such a bed. These are often very durable and can be used in many different ways or combined with other materials.
Raised beds made of metal should also be lined on the inside
Metal - a versatile and durable material
Whether hot-dip galvanized and shiny or in a modern "rusty look" in the form of Corten steel - metal is an attractive and very durable material that is also very well suited for round or curved bed shapes. Metal raised beds are also often provided with a so-called "snail edge", so that the voracious pests actually have no access to the fresh greenery. Raised table beds made of light sheet metal are particularly recommended for the balcony. These take up very little space and do not overly stress the statics. In principle, very different metal materials can be used to build a raised bed, but you should better keep your hands off potentially dangerous raw materials that could emit toxins into their environment. Disused railway sleepers, for example, are not suitable for a raised bed.
Types of metal raised beds
Metal raised beds offer a lot of variety: In addition to Corten steel with its rustic patina, galvanized raised beds made of sheet metal, powder-coated and / or painted in different colors of steel, iron or aluminum are also available. In addition, metal can be combined very well with other materials: You can fill gabions (wire mesh baskets) with stones and use them as a border for the raised bed or add wooden slats to a frame made of aluminum struts. The great robustness and stability of the material is the same for all types - which also blends in visually with modern gardens. If you want to buy a raised bed for the balcony or terrace, you should be careful: not all metal raised beds are lightweight.
Advantages and disadvantages of the different materials
Raised beds made of patina or corten steel have an interesting, rustic look due to the rusty red color. However, this patina also has a disadvantage, it stains heavily, especially on new raised beds, or can even be wiped off in some cases. Only after some time does the rust solidify. Much more serious, however, is the fact that the rust continues to eat through the steel and the material therefore becomes obsolete more quickly. On the other hand, raised beds made of stainless steel are much more durable, but they are also very heavy and unwieldy. Aluminum, on the other hand, is lighter (and therefore also well suited for the balcony). If you use iron or copper as materials, plan for their corrosion right away - untreated iron rusts and copper of the same kind develops verdigris over time due to contact with oxygen.
Build metal raised beds yourself
There are many different metal raised bed kits on the market. You will find the right raised bed for every purpose, but you can also build one yourself from your own materials. For example, metal plates can be welded together as desired, creating a stable box for the planting. The only disadvantage is that once parts have been welded together, they cannot be separated again and these are of course immobile. Instead of slabs, palisades, dug vertically into the ground, are also suitable for framing a raised bed.
Line raised beds with metal
The manufacturers of prefabricated kits often claim that it is not necessary to line the metal raised beds with foil. The material would not require any moisture protection. Nevertheless, it makes sense to line it with bubble wrap, for example, as well as an insulating layer of polystyrene foam or, if you want it to be ecological, softwood fiberboard. In contrast to wood or plastic, metal is an excellent conductor of heat, which can become a problem in both high summer heat and winter frost. The heat is conducted through the metal border into the interior of the bed, so that the plant roots are literally "cooked". In winter, on the other hand, the metal has no protective effect whatsoever, for example to protect the roots of perennial plants from the cold. An insulation (which of course has to be protected from moisture with foil) between the metal wall and the filling is therefore essential.
tips
Special care oils are commercially available that can be used to seal the surfaces of the metal raised bed against the ingress of moisture. Their use is particularly useful for raised beds made of corten steel or other corroding or oxidizing materials.