THE COMPOSTING RAISED BEDS

The technique of composting raised beds also known as the ‘mound culture.’ is the use of rotted wood and other organic materials to create low-input raised beds that are highly water retentive and self-feeding. It is a method that is based on the simple principles of decomposition that, when done properly, provides nutrients to the plants without the need to add externally acquired fertilizers for years while at the same time holding what water they receive for extended periods. They are therefore well suited to dry climates and production in areas where fertilizers are not desired, aren’t accessible or are prohibitively expensive. This method can be used in virtually any area to create permaculture beds that are essentially self sustaining indefinitely with the proper care and cultivation.
Mound culture beds are similar to other raised beds in composition apart from one key difference: the beds are built on top of a stockpile of rotted wood and other composting biomass, be it duff, leaves, wood chips or whatever else may be on hand. Because of the large mass of all this, the beds will necessarily be built high and so are most often the site for the bed is dug out a few feet. The depth to which the troughs are dug is determined by preference, the amount of time and effort one is willing to spend in building the bed (though this part is obviously greatly facilitated by the aid of heavy digging equipment), how hard the soil is and so on. For example, were you to want to make a mound bed in a neighborhood where there are restrictions regarding the appearance of a yard, it is possible to make the bed rise only a foot off the ground when in reality it may reach as far down as six feet. Most sources recommend a total height of at least four feet and ideally around six feet when the beds are completed, especially since much of this height will be lost in the first couple of years as the organic materials break down and thus compact slightly. If appearance is not an issue or there is only a limited amount of wood and organic materials available, it is perfectly suitable to simply build your beds on top of the existing ground level although you will then have to import soil from elsewhere. Typically the troughs are dug to a depth of about two to three feet with the soil and sod set aside separately, filled in with the rotted wood and other biomass, covered with the turf inverted so the soil side is up and then covered again with the remaining soil. After this, the beds are ready to be planted; indeed, as we will see later, there is good cause to plant the beds immediately.
It is possible to use a huge variety of materials, locations, soil types and so on when making a mound bed. There are, however, a few considerations that should always be made before building one. Location is the first and foremost of these. One should take several factors into account when choosing a site for the bed. Sunlight, as always, is the foremost of these, and as such the beds should be oriented to maximize sunlight throughout the day (South-North Orientation). If you wished to grow plants that needed indirect light, an east-west orientation would give you one side that received less light through the course of the day. Slope is another important consideration, and if the beds are to be built on a sloping surface it is perhaps the most crucial. This is because the beds are so absorptive that if they are not oriented properly with the flow of water, they will become over saturated. Were your beds to run perpendicular to the slope then those at the top would catch all the water, leaving those at the bottom deprived and dry. If the opposite orientation is employed, the water would simply sheet down the hill which could lead to massive soil sloughing and even landslides. Therefore, what Holzer is suggesting is that you take note of which way the water flows and then position the beds on a slight bias to the slope with offset breaks between them. This way the water will flow down along the sides of the bed allowing them to absorb some but all until it reaches the end of the bed and then passes through the break, down to the next row of beds, thus evenly distributing the water between all beds while slowing its roll down the hill. Accessibility is another factor worth going into. The placement of your beds should be in an area that is easily reached and that can accommodate the desired length and height of your beds with plenty of room between them and on the ends to facilitate plantings and harvests.

Though the choice in plants ultimately comes down to what you wish to grow, as with any permaculture scenario it is always to have a well thought out and diverse array of species that will complement one another in their growth. It is also important to think about planting deep rooted perennials for two reasons: one because they will add to the overall structural soundness of the bed but also because their long roots will draw moisture up to the benefit of other, shallower rooted plants. Another important factor to bear in mind is decomposition level of the organic material used in the bed previous to building. If your materials are small and only slightly composted, then you can expect high levels of nutrient release in the first few seasons and so you should plant accordingly with high demand plants such as cucurbits, night shades, and apiaceae (Holzer, 2011). You can then move on to less demanding plants like legumes (even better as they will fix nitrogen and add to the fertility of the bed) in later years. Mulch crops are also recommendable, and these again will be determined by all of the factors stated above. Strawberries are a good example, as they spread easily, are good for shading out the ground beneath, are hardy enough to be cut back to make room for planting and have the added value of producing an edible fruit. It will also be to your advantage to plant a resilient cover in the aisles between your beds; something that can withstand foot traffic but at the same time keep the soil in place.
Again, the best part of hugelkultur is how open-ended it is at every turn. As long as the basic principles are in place, then chances are your beds will flourish. Hugelkultur may afford those who have little water a viable option for growing much more than they could without the massive water storage capacity of the wood. It also creates an excellent use for wood and other biomass that might simply go to waste otherwise. If nothing else, it provides an interesting experiment that is a great alternative to normal raised bed gardening. This article really only scratches the surface of possibilities regarding hugelkultur. Its applications and variations are seemingly endless, they need only be implemented and, of course, shared with the world.
 For more reading visit: http://www.agrowingculture.org/2013/04/hugelkultur-the-composting-raised-beds/