Raised Bed Layers: Structure & Number of Layers

Filling a raised bed correctly is essential for healthy plants and a rich harvest. We explain which layers belong in a raised bed and what purpose they serve.

After Building a raised bed filling is the last step before sowing and planting begins. A system made up of different layers has proved its worth. In this article you will learn everything about the structure of a raised bed, the individual layers and their functions.

Why should you layer a raised bed?

The layered structure of the raised bed filling basically mimics the natural processes involved in the formation of humus. From the top down, the materials become coarser, larger, and more difficult to decompose. This means that there is a food supply for soil organisms over the years, which, through their tireless work, release nutrients for the plants in the raised bed. This is particularly important as the raised bed is largely cut off from the outside world. The stratification in the raised bed also regulates temperature, ventilation and water balance. It is used for drainage and at the same time stores water, which is particularly advantageous in summer.

How often do you have to refill a raised bed? In the first year, the soil in the raised bed can sag significantly, but the difference in height can initially be easily filled with high-quality potting soil. The layers decompose over the years and after about six to seven years the raised bed should be emptied and stacked again. The one that emerged from the previously lowest layers humus can basically be distributed anywhere in the garden.

What layers does a raised bed have?

The layers of a raised bed mimic the decomposition process from bottom to top. Depending on the height of the raised bed, each layer should be 10 to 25 cm high. Traditionally, branches, root wood and smaller tree trunks are layered in different thicknesses at the bottom of the raised bed. In order to further improve the water drainage, you can occasionally install larger stones. The bottom layer of the raised bed is followed by a filling or base layer, which consists of shredded wood, leaves and plant and lawn clippings. This material has a broad attack surface for decomposing microorganisms, so that it decomposes much faster than the coarse branches of the bottom layer.

This is followed by a layer of well-ripened compost, from which numerous soil organisms feed and thereby deliver nutrients upwards. Our Plantura organic compost improves humus formation, promotes soil life and is ideal for filling raised beds as a compost layer. It is completely peat-free and clearly CO₂-Reduced production in Germany. The last and top layer in the raised bed is a level of potting soil. But which soil should you use for a raised bed? The following applies here: A high-quality, nutrient-rich potting soil is the best choice in the raised bed, as it is suitable for most types of vegetables and herbs. Our peat-free Plantura organic tomato and vegetable soil has all these qualities and comes to you in sustainable packaging via climate-neutral shipping.

At a Glance: How to Layer a Raised Bed

• Lower layer: Thick branches, tree trunks and stones.
• Filling layer: loose, chopped up plant material such as plant and lawn clippings, leaves or wood chips.
• compost layer.
• Plant layer: Nutrient-rich potting soil with a finely crumbly structure.

Can raised beds only be filled with soil?

The layered structure of the raised bed is advantageous, but of course optional, because the bed can also be filled with pure potting soil. This saves work and can be realized with few materials. In the first year there will usually be no difference to layered raised beds. However, the water storage is usually poorer, so that it has to be watered more often. The big disadvantage is that many of the nutrients contained are completely lost after a few years are used up, since no supplies are brought up by the decomposition of the lower layers will. Soil life also finds hardly any nourishment in pure potting soil, which reduces fertility in the long term. The result is often that you have to fertilize a lot and more often so that the plants on the raised bed do not suffer from nutrient deficiencies and do not grow stunted.

Layer low raised beds

Raised beds, especially in the city garden on the balcony and terrace, are sometimes very low, so there is hardly any space for all four layers. Here you can reduce to the essentials: At the very bottom, a layer of stones, leaves and wood chips that promote drainage and ventilation. Fill in the compost layer on top of this, from which nutrients are converted. The final step is the planting soil layer in which the cultures take root. The smaller the raised bed, the narrower the lower layers will be. The top layer of plants should always be at least 10 cm high, preferably 15 to 20 cm high, to provide enough space for the roots.

Once all the layers have been filled in, it's time for them Planting of the raised bed. In our article we have put together useful tips and plant combinations for a rich harvest and pest control.