Raised beds are now known and popular among many gardeners. The Internet offers countless “building instructions” and the garden trade offers a variety of ready-made kits, made from a wide range of materials. No wonder that the raised bed is booming, because it has some advantages to offer over the classic ground-level flat bed. However, the precursor of the raised bed was the mound bed, which has its origins in China, where it has been used for centuries. About 50 years ago, European organic gardeners also began to take an interest in these special beds. From the mound beds then developed the special form of the raised bed, which is ultimately a mound bed enclosed all around. It is, so to speak, a raised bed in a box.
Raised and raised beds: the advantages
Before we turn to the layout and construction of the raised and mound beds, let’s take a look at the advantages that these two types of beds offer:
- Hill and raised beds are very rich in nutrients due to their composition (see below). The natural rotting process creates a rich soil life that guarantees long-lasting fertility. Strictly speaking, these beds are a kind of planted compost pile. Therefore, in the first two years after planting, they are intended only for so-called heavy growers, which require a lot of nitrogen: Eggplants, cabbages (e.g., white cabbage, cauliflower), potatoes, squash, cucumbers, melons, zucchini, tomatoes, peppers, and beets. These plants reward location with high yields! However, for all other plants, especially spices and medicinal plants, such beds are clearly too rich in nutrients. Only when rotting is well advanced (in the third year), even weak growers can take hold on hill and raised beds. Otherwise, there is a risk of overfertilization, combined with nitrate accumulation that is hazardous to health.
- Another advantage of raised beds is the rotting process that takes place in them, which leads to heat development, which in turn promotes plant growth. Especially in the first year, the soil temperature is measurably increased, which primarily benefits heat-loving plants (eggplant, tomato, chili). Temperature advantages of up to 5 °C are possible. In addition, plantings and sowings can be made somewhat earlier due to the soil warmth.
- Mounding and raised beds also offer the opportunity to put garden waste to good use. Anyone who has a lot of hedge trimmings, tree prunings and leaf litter will be very happy about this “profitable” disposal option. Since especially in autumn a lot of green cuttings, leaves and garden waste accrue, this season is a good time to create such beds. But also in early spring there is often a lot of rotten leaves and hedge cuttings available.
- An advantage that can be cited especially for the raised bed is the working height. You can actually garden there in a way that is easy on your back, which can be an important argument, especially at an older age.
- Compared to the flat bed and raised bed, the raised bed has the advantage that the cultivation area can be increased by about one third due to the curved hill shape.
- The advantages outweigh, but there are also disadvantages
- But there are also disadvantages: The construction work of the layered mound beds and raised beds is quite laborious and time-consuming. In addition, mound beds and raised beds attract mice and voles through their substructure, which can then cause great damage. Accordingly, you need to introduce protective measures when building with wire mesh (see below). On the subject of pests, you can still mention the slugs, which can be easily controlled and kept in check, especially on raised beds because of the border.
Create a raised bed: This is what you should consider when building
The location should be as sunny as possible, and the bed is best laid out in a north-south direction. The optimum width is between 1.60 m and 1.80 m, so that all areas of the bed can be well worked. The height of the finished hill will be about 60-70 cm. The length can be determined at will.
First, a 25 cm deep pit is dug in the size of the bed. In the process, you should store separately sod and excavated earth, because you will need them again later. To protect against voles, this pit is lined with fine-meshed wire mesh.
Now begin to layer in the various materials: First, fill in coarsely shredded pruning waste from trees, woody plants and hedges. If possible, chop them beforehand, which accelerates rotting. This layer should be filled in about 30-40 cm high as a mound.
Now follows a layer about 25-30 cm thick of shredded sod, leaves, straw or mown material. If there are no sods, mix in some soil from the excavated earth. Dry materials should be sprinkled with water.
This second layer is now covered with semi-mature coarse compost or manure, about 20 cm high. In this way, the shape of the hill can be modeled more clearly.
The top cover of the mound consists of good garden soil, enriched with some mature compost. In this layer, the excavated soil can be used, if it is good garden soil. This final layer has a thickness of about 20 cm.
All four layers should be well consolidated during the construction. Now nothing stands in the way of planting.
Over time, the raised bed will flatten out somewhat. The useful life of a raised bed is about 5 years, then you can remove it. During this period, the inner filling rots, which can now still serve as a good humus.
The popular raised bed in contrast to the mound bed.
The real difference between a raised bed and a raised bed is the box-shaped border. The trade offers numerous raised beds in a kit, but with a little “craftsman experience” it can also be constructed well yourself. The raised bed can be edged with a wide variety of materials. Visually beautiful are the natural materials wood and natural stone. It offers itself to use weather-resistant woods such as larch or Douglas fir, but there is also the possibility of upcycling and wooden pallets to process. Here you can find instructions for a DIY raised bed in Waschbär magazine. As an alternative to stone edging, there is the option of using the currently popular gabions, which are metal mesh baskets filled with stones.
The size of the rectangular or square frame construction depends on your own preferences. The width of the raised bed should be about 1.20-1.40 m, so that you can easily work all areas. The height should be planned between 70 and 90 cm, depending on the size of the gardener. The length can be determined by everyone according to their own needs and ideas.
The raised bed, like the raised bed, has direct contact with the soil, so that the soil life can migrate. The small animals and the microorganisms are absolutely necessary for the conversion processes in the bed filling. Raised bed systems that are closed at the bottom are not optimal. It is then ultimately a large planter.
Building and filling a raised bed
To protect against voles, it is also necessary to lay a wire mesh inside the frame structure. If the frame is made of wood, it is worth protecting it from the damp filling with a film.
Filling is broadly similar to the construction of the raised bed: first comes a layer of tree and hedge cuttings about 20 cm thick, possibly chopped. You can also integrate bark mulch into this layer.
Then follow about 30 cm of garden waste, possibly also chopped straw and leaf and lawn clippings. A few centimeters of normal garden soil can now be interspersed for demarcation.
This is followed in a third layer by 20 cm of coarse compost or manure.
Finally, mix good garden soil (topsoil) with finished compost and fill 20-25 cm high. Now the construction should be filled up to the working level.
As a rule, it takes 5 years until the plant material rots and the bed slowly “sags”. If necessary, in between fill from the top with compost, garden soil or a ready substrate.