How to Make Vertical Raised Beds for Urban Green Spaces
With our cities getting denser and more populated, how can we create beautiful and productive urban green spaces for all to enjoy? Emily explores the potential of Sepp Holzer's Raised Beds...
The popularity of our recent articles such as downsizing; sustainable cities and low-impact transport options proves that permaculture is not merely a solution for smallholders, farmers and families living in the countryside, but for city dwellers too. Living in cities offers great opportunities for us to reduce our footprints.
This may seem like a misnomer but think about mass transit; high density living; the potential for sharing tools, equipment and facilities; and a wealth of community and entertainment options available on your doorstep.
The perception that cities are a carbon hungry way of life lays largely in the footprint associated with transporting food and other provisions to geographical areas which do not provide for their own subsistence needs. But this isn’t a reason to give up the joys of city life just yet. In this reader solution we look at more ways to encourage food security in urban areas.
Why choose raised beds in an urban setting?
How about introducing a raised bed in to your community growing space? These are easy to get started and have so many incredible benefits, such as:
- Increasing the yield of food from a small space
- Absorbing rain water, releasing it slowly over time, reducing the pressure on storm drains and aiding in flood protection
- Using up waste from garden clearing, thus reducing disposal costs
- Creating a community space which can be used for adult and child education, or as a sheltered chill out space – the raised beds can provide a barrier to city noise pollution
- The beds can be arranged to create a visual barrier to an unattractive urban landscape
- Being suitable for growing all kinds of vegetables
First, creating your raised bed...
Raised beds should be at least 1-1.5m high. This allows for a fantastic increase in growing space, whilst ensuring that most adults will be able to harvest the food without treading on the bed and compacting the soil.
Observe the wind direction, and plan to develop the bed as wind break, so running with its length at right angles to the wind direction.
A trench should be dug (great opportunity for getting the community involved), and filled with garden waste which will rot slowly and release nutrients over time. The life expenctency and potency of nutrients depends on the type of waste you put in – if you use chipped wood (which breaks down quickly), a large amount of nutrients will be released in the first year.
To make the most of this, Sepp Holzer suggests “selecting plants that demand a very high nutrient content: pumpkins, courgettes, cucumbers, cabbages, tomatoes, sweetcorn, celery and potatoes to name a few. In beds like these it is better to cultivate less demanding plants like beans, peas and strawberries after three years. If they are planted any earlier they might become overfertilised, and not develop a good flavour.” Where you are able to use fallen tree trunks these will rot down very slowly, providing nutrients to the soil slowly over time.
If you can get hold of it, cover the material you want to decompose with a layer of turf, grass side down, and cover this with the material you excavated. The slopes should be at least 45 degrees, and up to 60-70 degrees if you want to increase the growing space in a constricted area.
Many raised beds ‘fail’ because they are less steep than 45 degrees. This leads to compacting of the soil, so new plants cannot establish themselves as well as they would in loose soil. It also restricts the amount of oxygen getting to the decomposing material, resulting in anaerobic rotting, which will smell unpleasant and have a negative affect on the plants.
Here is a simple table of dimensions, to save you the trigonometry!
Next, planting the bed...
The beds should be planted immediately while the soil is still loose. Raised beds are suited to growing all kinds of vegetables: peas, beans, salad, tomatoes, radishes, cucumbers, carrots, courgettes, pumpkins, potatoes and many others; with fruit bushes growing very effectively on the crest of the bed. If you wish to use the raised bed as a windbreak, make the sides steeper (60-70 degrees) and plant the top with tall plants such as sunflowers, hemp and Jerusalem artichokes.
As ever, mulching with straw, hay or newspaper is an effective way of keeping away the plants you don’t want, and also ensures that moisture is retained in the soil. This will reduce the need to water the bed in dry periods, ensuring low maintenance.
Depending on the weather and how they are used, the raised beds flatten gradually over the years. They are then either rebuilt or replaced.
Finally, encourage food growing in your community...
As Sepp notes in Sepp Holzer’s Permaculture, “an appropriately designed raised bed system can make an excellent and relaxing pick-your-own area. By harvesting food for themselves, the visitors feel connected with nature and can convince themselves of the high quality of the produce.” You can invite schools to your growing space so that children and teachers alike can learn about the potential of sustainability in urban spaces.
Other members of the community can be invited on work days, especially useful when digging the trench and filling it with garden waste. Why not let your helpers come back in a few months and reap the harvest of their efforts?
Where you have the space, raised beds can be arranged to create a maze or around a central focal point like a pond or orchard.
Produce can be sold to raise revenue for the project, and the area will be adequately sheltered from traffic to provide a relaxing oasis in an urban setting, or the perfect location for a community party!
Emily Ingham is a former environmental consultant.
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Lovely descriptions and illustrations of space-efficient living. Thank you! it would be fascinating to know just how much we can increase the growing area of the planet just by adding raised beds and berms of various kinds in every possible place!
The pictures are beautifully drawn and very inspiring but in my admittedly limited experience of creating hugelbeds I found that the main limiting factor was the lack of soil and turf to create the classic high design illustrated here. With regards the turf (assuming one is to only use that which is removed in creating the bed), how can an area of turf that originally covered flat ground now cover a huge raised hump like in the picture (whose base is the original flat area)? I find it just isn't that stretchy! And a similar problem occurred with 'stretching' the amount of soil I was able to dig out of the ground before reaching sub-soil. I don't think the top-soil layer on my allotment is particularly thin but no way could it be stretched out to adequately cover the increased surface area of a 1m hump. Using sub-soil for this seems to go against the principle of not disturbing the soil's micro-biology too much, and not expecting sub-soil to be able to behave well as top-soil, at least not for a while.
So is one supposed to use soil and turf from elsewhere? If so where? I am adopting the principle of not bringing anything onto my land that I can't haul there on a push-bike and trailer, just to see whether eliminating fossil-fuels from my inputs is a workable possibility. So the other option is to rob top-soil and turf from other areas of the allotment. To some degree this is a possibility. If I dug out my paths down to subsoil level then that would produce useable material, but somehow that doesn't seem right, and also at present, due to a lack of other mulch, the grass 'crop' from my paths is a resource I am reluctant to sacrifice. Hmmn...
Also, with regards orientating hugelbeds as wind-breaks, I did this with mine, and was in fact one of the factors in deciding to create them, but due to the prevailing winds being south-westerly this also meant they were acting as significant 'sun-breaks' too. Because my humps aren't very tall (due to lack of soil and turf!) the shady sides are quite useful providing alternative 'micro-climates', but with a 1+m hump, with fruit bushes on top as mentioned in the article, the shade they would be throwing across the rest of the allotment would be significant - and I am already struggling to find enough variety of good cropping plants that I want that are happy enough in the amount of shade I have already created due to other vertical-growing, wind-break structures.
I would really appreciate some comments and advice on these predicaments as I'm sure a lot of people will have encountered similar when trying to put good-looking theory into practice on small areas of land such as my small allotment and many space-limited urban settings. I can easily see the wonders of hugelbeds when you've 40 hectares to play with like Sepp has!
I'm still a firm believer in burying the carbon resource of twigs and small branches that I gained from my back hedge being laid last year, and am very glad that I did, and my 1ft humps have proved to be better than nothing in many ways, but I do wonder why the 'text-book' approach insists on such height, with no mention of where the extra materials needed are to come from, and the effects of shading.
Thank you for reading!
Where does the "extra" material (turf, soil) come from? How do you deal with the substantial amount of shadow these tall ridges create? And finally, how do you keep your soil piled so high WITHOUT compacting it some... and, with it so high, how do your plants (1 meter above the decomposing stuff) get any benefit from your organic debris in the base of the "hump?"
Reasonable questions Silver Raven and Summer.
The basic answer is this: the system described is a Hegelkultur bed, just one style of raised bed, and is really designed for use where you have an ample supply of 'waste' material - logs, trimmings, woodchip etc. The key premises are these:
1. this system is essentially a microbial farm - the balance of woody material and soil helps to generate both a mycchorizal fungus and beneficial bacteria rich complex.
2. the decomposition generates heat. really helpful for creating'out of season' or 'out of zone' growing microclimates in coller areas - Holzer is Alps based.
3. the spongey material generated as the wood decomposes is a fantastic water retention system. i use these in Melbourne, Aus, and in our chronically dry summers these beds are often the only ones that survive through a stretch of days approaching 40degreesC.
Personally, I wouldn't recommmend HK beds for small spaces. Also, the light restriction can be dealt with by orientation and distance spacing between beds. This methoid is all about shifting microclimate and soil biology. CONTEXT is everything. It sounds like in your situations a basic no dig bed that you can build gradually would be more appropriate. hope that's helful.