Posted: 10/02/2015 at 19:52
I garden on very heavy clay now so raised beds are a must. I used 6" boards and by the time I had double dug the beds the soil had raised itself up a couple of inches without the addition of bought in topsoil. Over the last 3 years It has gradually built up by the addition of homemade compost, the soil out of containers and grow bags and leaf mould. In another couple of years I will be having to think about replacing rather than filling!
I created my first raised beds over 40yrs ago by simply using the turf I took off the surface to make a low wall around the edge. This worked very well and over time the beds rose above this level and had slightly sloping sides. I eventually edged these with home woven willow edging that looked quite nice; but if I was doing it today would plant step over fruit to edge a bed thus creating something nice to look at and also productive.
I think the most important issue is to make the beds narrow enough to be able to reach the middle without treading on them. For me this would be no more than 4'