I am relaitvely new to raised beds and I am curious about them, because of what I see at the Blackpool community garden. When I was living in the UK a current trend is not to water the garden hardly at all. The reason for this is that roots follow the water. And it you water the plants the roots grow upwards, or at least remain near the surface. Unless they get a really good soak. So if you do not water frewquently the roots go down to where there is water. In England it is usual for it to rain and so there is usually water somewhere under the surface.
Now, in a raised bed, are the plants even further from potential water in the ground? At the Blackpool garden I noticed that the soil in the raised bed would get dry very quickly, and the grass around the raised bed would still be green. Maybe indicating that the soil in the ground still has moisture a few cm below the surface.
So, can you plant a raised bed, by digging out the poor clay in the soil, and then putting the new soil in that dug out area. So it is not a raised bed anymore, but new soil in a wide hole. Would this not help to conserve moisture in the soil and hence require less watering?
Just being curious, and wanting to use less water.
John
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Thanks Laura for the reply, which I found very informative. But, I did not know that clay holds more water than humus? I always thought clay did not hold water well, and it needs humus to keep the water? So I am intrigued by this. I agree that compost or humus should be added to existing soil, but I tend to dig out as much clay as I can find. Or at least mix it with sand so that the clay can break down a little, and provide aeration.
Further to Christy's suggestion re drip irrigation.
I have 2 raised beds 1.5m x 3m. I bought a couple of inexpensive black soak 15m hoses from Mitre 10. They're just the right size for one bed. Set them under the mulch, turn them on for an hour every few days. No wasted water. Works a treat.
I never dig the beds. In fact I thought that was standard practice for raised beds. Just don't let anyone stand on the soil. My labrador's a prime culprit. Greedy sod can hear a fridge foor open 5 miles away and can locate a ripe tomato in impenetrable jungle. She leaves very deep footprints on my carefully nurtured living earth!
You might find the video about the 'no-dig garden' of interest. Its a raised garden, but the thing that really appeals to me is that you don't have to dig it. Take a look at this link http://www.yates.co.nz/garden-guide/videos/no-dig-garden/. I have just built one and am about to fill it up at Easter.
Currently, I have lots of raised garden beds that were built on top of clay soil. I bought in soil initially, and added home-made compost to build up the soil goodness as well as lime and other organic matter. They have worked well, and I've noticed an improve in what's growing there over the years as the soils improved.
Clay will hold much more water than pure humus, so why not employ common sense and use both?
In my garden I have quite simply mixed the clay soil (and a lot of it was yellow subsoil with no humus at all in it) with compost. I have not imported anything at all from outside except for some hay bales to get the mulching started.
Obviously it will be more difficult to grow enough compost and mulch material on a small suburban section, however there will always be neighbours who want to get rid of their shrub or lawn clippings (check if they spray before you accept the offers), which can be used to increase the size of your compost heap.
So I would suggest you incorporate some clay into your compost (I have done it other way round and incorporated the compost into the clay) then you would be all set for dry summers and also for wet winters and the compost would actually be much more stable. Most organic gardners would be horrified if they checked how much carbon they release with their composting :)
...they do dry out fast - I would always heavily mulch raised beds, and ideally use a drip irrigation system with pipes under the mulch layer. overall here on waiheke i think they are a good idea for annual food crops, drainage can be a big issue in winter and spring, and they are at their best in spring when they dry out faster and warm up faster than non-raised beds, meaning you can get an earlier start to the season. but as you point out you have to be extra vigilant over summer when it's dry, plus not much water around...
Thanks for the feedback Gayleen. I have heard about the improved access, but I have yet to witness a NZ winter, I see now about the boggy situation. Especially if you do it in clay, which is what most people have. So as long as you can water the raised bed frequently in the summer then raised beds might be a good idea. At Blackpool the watering was forgotten for a long time and the plants almost died twice, so it got me thinking...
yes this would conserve water, however it could get boggy in the winter, as you are creating a sink. also you loose the benefit of a raised gardening, that is easy access - especially as one gets older! and good drainage also
Replies
John
I have 2 raised beds 1.5m x 3m. I bought a couple of inexpensive black soak 15m hoses from Mitre 10. They're just the right size for one bed. Set them under the mulch, turn them on for an hour every few days. No wasted water. Works a treat.
I never dig the beds. In fact I thought that was standard practice for raised beds. Just don't let anyone stand on the soil. My labrador's a prime culprit. Greedy sod can hear a fridge foor open 5 miles away and can locate a ripe tomato in impenetrable jungle. She leaves very deep footprints on my carefully nurtured living earth!
You might find the video about the 'no-dig garden' of interest. Its a raised garden, but the thing that really appeals to me is that you don't have to dig it. Take a look at this link http://www.yates.co.nz/garden-guide/videos/no-dig-garden/. I have just built one and am about to fill it up at Easter.
Currently, I have lots of raised garden beds that were built on top of clay soil. I bought in soil initially, and added home-made compost to build up the soil goodness as well as lime and other organic matter. They have worked well, and I've noticed an improve in what's growing there over the years as the soils improved.
In my garden I have quite simply mixed the clay soil (and a lot of it was yellow subsoil with no humus at all in it) with compost. I have not imported anything at all from outside except for some hay bales to get the mulching started.
Obviously it will be more difficult to grow enough compost and mulch material on a small suburban section, however there will always be neighbours who want to get rid of their shrub or lawn clippings (check if they spray before you accept the offers), which can be used to increase the size of your compost heap.
So I would suggest you incorporate some clay into your compost (I have done it other way round and incorporated the compost into the clay) then you would be all set for dry summers and also for wet winters and the compost would actually be much more stable. Most organic gardners would be horrified if they checked how much carbon they release with their composting :)
Thanks, John