Of course, you can only fill a raised bed with soil, but this only makes sense for very small or rather flat raised beds (such as table beds). Instead, raised beds should always have drainage so that excess water or rainwater can run off.
A raised bed always needs drainage
Why water drainage is so important in raised beds
Such a layer is particularly important if the raised bed is on a sealed surface such as a concrete slab or a paved yard. Excess water must be able to drain away unhindered, especially in winter, otherwise waterlogging will form. This in turn hinders the growth of the plants and ensures that the roots rot and fungal diseases spread. If a raised bed is only filled with soil, this makes water drainage more difficult - the heavier the substrate, the more likely it is to compact. In addition, the garden soil does not usually consist of a thick layer of topsoil, here too only the first 40 centimeters are fertile soil, often followed by a layer of clay or sand - depending on the composition of the soil.
Which materials are suitable for drainage?
There are different ways to create a drainage. With the classic layering, which is mainly used for raised beds on loose soil, coarsely chopped branches and twigs as well as wood chips and bark mulch as the bottom layer ensure that no water accumulates in the bed. However, these materials decompose very quickly, so that the bed contents can suddenly sag within a few weeks to months. To prevent this, you can click instead
- thick, slowly rotting stumps of hardwood
- Gravel, crushed stone, lava pumice
- grit,(46.95€) sand
- Rubble, smaller boulders
- or slabs or paving stones
To fall back on. Concrete slabs and paving stones, for example, are layered in such a way that gaps remain for the water to drain away. Pour sand, grit or gravel in layers into the cavities. Even thick stumps of wood (e.g. oak, beech, larch or robinia are very suitable) need filling in the gaps.
Create a drainage layer - this is how it's done
If the raised bed is open at the bottom, you must close it with a fine-meshed wire (e.g. rabbit wire) so that no bugs can get in from below. You pour the drainage layer on top of this, whereby fine-grained material such as sand, grit or gravel can simply be filled in with buckets. Coarser material is filled with finer bulk material and compacted. Place a drainage fleece over the drainage layer, this prevents substrate particles from getting stuck in the interstices of the drainage.
tips
Raised beds that are sealed at the bottom must have drainage holes in the lower area on the side of the walls or in the foundation. If you have a terrace with a slope, you have to set up the raised bed in such a way that the water can flow away from the raised bed and does not stand in front of the bed.