I'm getting ready to build my wife an herb spiral right off the patio from our kitchen. It's by far the best location based on proximity, but the problem is it's on a fairly steep hill and I'm wondering if that'll be a problem. Leveling the area would be impossible, I think, because of the structures around the area. It's a south facing slope with full sun all day, and the slope is probably about a 1 foot rise across the 5 foot diameter of the spiral.
Does anyone have an opinion on whether this will work? Anything I should consider? Should the lowest point of the spiral be at the top of the natural slope?
Dean, I am trying to see in my mind how that would be built. I am almost thinking that it would be, not a complete spiral, but a series of 1/4 spirals, or flattened U shapes, from the bottom of the slope upwards, Then as you gain a more level "terrace" you could make the full spiral. Not sure if that makes sense?
I would think you could just do it. The spiral itself will probably be a little irregular at the lower end. Think of a slinky hanging, and lift up one side a bit. Sure, a couple of the coils might touch, but I don't think your herbs will mind. Just sort of eyeball it and go from there. Probably starting at the lower side would mitigate it the best. Is there something more complicated I'm missing?
Aside from being a beautiful shape the spiral does actually have a purpose (providing different microclimates), but I wouldn't get hung up on the superficial form over actual function.
If your slope is really steep, it might be awkward to access the spiral from the upper side. I would consider a series of semicircular arcs, some set into the slope and some rising out of it, and all accessible from below. Putting the bed on the uphill side of a natural path would make much of it accessible without severe bending.
All of this does depend on your particular climate and site specifics. Is your area more damp and cold, or hot and dry? How is it oriented to the sun? Etc...
Dean, I think it's definitely worth an experiment, and I wouldn't want to discourage anyone from trying out a design, but I suspect you will find that a spiral is not the right shape for that location. Spirals in nature occur in eddies where a current passes an unmoving area; in a garden that would correspond to a heavily trafficked path passing a less trafficked area. On a slope, you're looking at a sheet flow of both water and air, which you can encourage by building along the slope or discourage by building across it. Permaculturalists typically try to slow down the sheet flow with swales, windbreaks, or other long structures built across the slope. Additionally this makes working on the garden less difficult since you don't have to stand at an angle.
In my own experience, I built an herb spiral the first year I had my house, and I disassembled it less than a year later. I found that it presented too much of a profile to the wind, which blew the mulch away and dried out the soil. I now have a hügelkultur bed instead, oriented with its narrow end to the wind. Your mileage may vary.
One of the main functions of the herb spiral is to create a variety of micro-climates. Some spots will be wetter/dryer, have more/less sun, etc. I wouldn't get hung up on a spiral. It was designed with a flat yard in mind. If you have a slope, you've already got some of the variety you're looking for. If you add some TEFA and huglekulture, that should give you plenty of diversity in growing conditions.
@Miles - yes, that makes sense and I think if I did an o contour "U" at the bottom, I could probably add a spiral on top and achieve the microclimate and accessibility goals I'm looking for. In fact it kind of looks like maybe that's what Tracy did on hers.
@Tracy - see my comment to Miles. It looks like maybe you did the down hill section of your spiral as an isolated semi-circle, am I seeing that correctly? I think something like that would work for me. You have a beautiful place, by the way. I was checking out your little patch of paradise from the thread in your signature.
@Jeremy - Yes, that's a good description of how I was originally thinking about it. I'm probably over thinking this, but some combination of what you describe and what Miles suggested should do the trick. It's just tough to picture until I get out there and start digging, and it's too dang wet here to do any digging right now.
@Glenn - you guys are all much more creative than me. Another good idea! I think I'm coming to a good solution now.
Thanks everyone for your inputs. You guys are great. I hope someday when I get more work done on my farm I can share a lot more instead of just asking questions...
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