The shallow raised bed is raised 15 to 30 cm from the ground and bounded by a permanent frame, into which compost is usually poured. Place it on an existing garden bed or directly on a grassy surface, as 15 cm of filler suffocates the grass and weeds below it. The frame is often made of wood; it can also be made of brick or concrete blocks. When using wood, we avoid chemical protection. The width of the beam is between 1 and 1.4 m, or at most so that you can still reach half of the bed with your hand. The length is arbitrary, and we adapt it to our needs. The size of the shallow raised bed does not matter to the plants. The classic measure is 1 x 2 m.
We use air-dried wood coated with only natural preparations to arrange the garden and surroundings. When wood is in contact with the ground, it decays more quickly. Other enemies of wood are also constant weather changes, from frost and rain to direct Sun. The most durable domestic wood for outdoor use is chestnut, larch, acacia, and oak. Spruce wood, which is the most common for general use, is not durable, and its use in the garden is not recommended.
What Do We Grow in a Shallow Raised Bed?
All vegetables are suitable for growing in shallow raised beds. Directly sow or plant in a raised bed filled with compost. If we use a protective net against soil pests in the raised bed, we will be limited in growing parsnips, parsley roots, and other larger root crops, which penetrate the net with their main root and cannot grow. The raised bed provides a good foundation for the entire garden season and is therefore also ready for subsequent sowings.
The Preparation Process of Shallow Raised Bed
The procedure for preparing a shallow raised bed of 2 m2, placed directly on the grass surface, is described here. It will be raised from the ground by 15 cm, which is enough to completely “smother” the filler grass. We will use oak wood for the border.
What we need:
- Two oak boards with dimensions of 4 cm x 15 cm x 100 cm
- Two oak boards with dimensions of 4 cm x 15 cm x 200 cm
- stainless protective net against floor pests, dimensions 100 cm x 208 cm
- 6 wheelbarrows* of compost (or 4 wheelbarrows* of compost and 2 wheelbarrows* of wood chips)
- 0.5 l of linseed oil for wood
- 8 screws 5mm x 90mm
* 1 wheelbarrow = 70 l
Before assembling the wooden frame itself, the entire surface of the boards is coated twice with linseed oil. Wait 6 hours between the two coatings for the oil to soak into the wood. Apply the oil with an old cloth or a sock that you put on your hand. We can also use a brush. When absorbed, the oil fills the pores in the wood and thus prevents the absorption of water, which causes decay. Therefore, preparation of the raised bed takes a day or more but will therefore be more durable in the future.
Making the Frame
Drill holes for screws in the shorter board with a drill 2 cm from the edge on each side. Then, on a flat surface, we fold the boards into the final shape of the raised bed (rectangle), fasten the screws to fix the wooden frame, and put it in the final place. The terrain must be flat and without bumps.
The frame is then turned over to place a stainless protective net on the underside, protecting the vegetables from vole or mouse attacks. A denser mesh (window size 6 mm x 6 mm) also protects it from mole cricket. Align the protective net and fasten the initial part with a stapler. In this part, we also align the frame into a rectangle and cut the protective net to the final size if we haven’t already done so. The net should look a bit over the wood than leave a hole. We tighten it and fasten it to the end with a stapler at a distance of 20 cm. The frame with the attached net is turned around and placed in the final position. A shallow raised bed frame does not need to be fixed in the ground.
Filling the Shallow Raised Beam
Several combinations are possible for charging. It should be pointed out here that fresh organic material decomposes sooner or later. If we fill the raised shaft with fresh organic material, the level of the material drops significantly within a few days. The level continues to drop until fresh organic material has been processed. That is why we do not fill the raised beds with fresh organic material, and we prefer to choose compost for the filling.
We use the following three filling options, where the general rule is that less processed organic material fills the lower layers, and the highest quality compost is always on top.
1. Filler Option for Shallow Raised Bed
Six wheelbarrows of quality compost.
2nd Filling Option – When Partially Weathered Compost Is Available
Bottom 10 cm – 4 wheelbarrows of partially weathered compost.
The upper 5 cm – 2 wheelbarrows of quality compost.
3rd Filler Option – When We Have Very Little Compost Available
Lower 5 cm – 2 wheelbarrows of wood chips.
Middle 5 cm – 2 wheelbarrows of partially weathered compost.
The upper 5 cm – 2 wheelbarrows of quality compost.
When the first two wheelbarrows of compost are placed in the frame, the contents are raked over the entire surface, and the contents are walked. Then water abundantly. Shake the contents of the next two wheelbarrows, then rake, walk, and water. Add the penultimate wheelbarrow of material, then rake, walk, and water. At the very end, the last wheelbarrow of the highest quality compost follows, which we just rake evenly. The filled content is well compressed; the raised bed will not need to be additionally filled or loosened in the next two years. The shallow raised bed is thus already ready for direct sowing or transplanting seedlings.
Although we trampled the contents, it is still loose enough to make the holes for the seedlings with our hands. The cost of a bed prepared in this way, together with compost, is between €35 and €70.
Ideas, Extensions, and Usage of Shallow Raised Bed
Place the raised beam somewhere near the house. It can also be sown with herbs, spices, or other perennials. We can make a beautiful garden out of several raised beds. We start with one or two in the first season and add new ones in subsequent years.
There should be at least 40 cm of space between the individual raised beams so that we can maneuver the wheelchair in between. If we leave green on the paths, the distance must be wide enough to be able to mow with a lawnmower. It is easiest to mow the lawn with a string mower along the edges of raised beds. The intermediate paths can also be thickly covered with wood chips and thus increase the proportion of organic material on the entire surface of the garden. Mulch made of wood chips is then regularly added to the paths so that we don’t have problems with weeds.
With the raised shaft, we do not have to worry about water stagnating during heavy rain due to the minimal rise from the ground. At the same time, it is not necessary to water as often as high beds (higher than 30 cm) since the plants are closer to the ground and water is available to them from the ground.
With a wooden frame, ants like to appear in dry weather, so we also wet the wood when watering. In wet weather, however, snails like to stay near the wood. This is one of the few destructive features of raised shafts. Using wood chips on paths reduces the problem with snails, as they avoid the chips. Crops from raised beds are still easy to harvest, even with taller plants (long beans, cucumbers, tomatoes).
If desired, we fix a garden tunnel or a frame for a plastic container to the raised bed. This way, we create a microclimate to extend the season into the winter months. We maintain it in the long term by adding a new layer of compost, always filling it up to the height of the wooden frame.
When we use a net at the bottom, we are limited to parsnips and sweet potatoes when growing vegetables. We can always make a ridge in the middle of the compost pile, as the height of the raised pile should not limit us. Compost can be filled into the pile, or a raised pile can be placed on the part of the pile.