wicking bed, take 3

UPDATE: wicking beds lined with builders plastic do not last -- they develop leaks. Please read here for more info.

Summary:

This post describes a method of building a wicking bed using salvaged materials (except the liner). Total cost was about $40 (part roll of geotextile and builders plastic, few nails and screws).

Background

The Summer that is now finishing was not particularly hot by Adelaide standards, though the Spring was very hot and dry. We found that our tomatoes really struggled due to lack of water in their early growth, and our tomato harvest is very small compared to last year. Our most successful tomatoes were volunteers (self-seeded) that grew in one of our wicking beds.

Also, I've already planted out some brassicas (broccoli) in preparation for autumn in one of the existing wicking beds -- despite no rain and some very hot (~40 C) days, they're doing very well with only a few bits of extra hand watering.

So, I am building another wicking bed. 

Materials

Recycled or found:

• Lengths of meranti timber, 50 x 35 mm that I salvaged from a 1970s pergola that I rebuilt. Some of them are a bit rotten, so I've chosen good bits. 
• Sheet iron from a fence with a neighbour that was replaced (I kept all the iron and jarrah posts, though the posts were rotted away at the ground)
• Two 50 mm square tube posts from the garden
• Length of old garden hose from the side of the road

New:

• Builders' plastic (to create the reservoir)
• Geotextile (to stop all the soil mixing into the reservoir)
• Rivets and 40 mm screws

Method

I considered buying some railway sleepers or circular corrugated iron beds, but for a similar sized bed it would have cost $500 - $700. Possibly that would result in a longer-lasting bed, but I'm hopeful that this should still work fairly well, and cost much less.

The basic idea is that, because the timber is not strong enough to actually retain the soil and water, it needs to work under tension (as opposed to simply bearing a load). I think many garden beds are really over-engineered -- I'm not building a bunker -- just something that can hold in the soil. Note that it doesn't need to be strong like a retaining wall -- circles in tension are much stronger than a straight edge -- having the rounded ends makes it easier to build.

The design was inspired by a circular wicking bed I build before, simply by joining sheets of iron together with rivets. That design works well, and is very cheap and simple. Now imagine getting that circle, cutting it in two, and putting some square sides in between and that is what I'm doing. This is more complicated, but it gives a larger bed.

Basic design of the bed. There are straight side walls, reinforced with the meranti timber and vertical posts. I will add star pickets to the "corners" if needed for support at the base. The three timbers across the top are to hold the top together in tension so that the sides don't splay out.

 One problem with using meranti is that it will rot quickly if it has wet soil against it. At the bottom of each side, there is a piece that rests against the ground -- I've wrapped this in plastic to protect the timber.

The partially built bed. Note the plastic to protect the meranti that is in contact with the soil. At each end of this "box" I've now put a star picket, to give the bed extra rigidity. I'll do the same on the other side.

The 1/2 cicle at the end. It's not quite circular yet -- I need to move a bit more mulch away and push it out. Note the hose on top to protect people from sharp edges. I drilled holes through the iron and used cable ties to keep the hose in place.

An inside view of the bed. Before any plastic lining is installed, I will carefully go over all the internal surfaces and cover any sharp bits. I'm not quite sure how I'll do this yet -- maybe silicon, maybe tape

 The  reason I chose to fiddle about with reused materials instead of buying new, is just part of the thinking about consumerism. We're really conditioned to see buying things as the solution to a problem, and I'm trying to move away from that kind of thinking. Hence, I wanted to build it, as much as possible, with things I already had.

The plan is to try and find some old carpet, or underliner (synthetic, preferably) on the side of the road and use that to line the bed and protect the plastic sheeting.

The eventual plan is to give it a nautical theme, including a sail and some portholes on the sides -- maybe even an anchor :-)

I will post an update about this bed when it is finished, but in the meantime would appreciate any comments regarding potential problems people can see with the design.

Rest of the garden

We're getting a fair bit from the garden at the moment -- lots of curcurbits, capsicum, loads of basil, silverbeet and other leafy greens, some tomatoes.

This is a volunteer pumpkin that we've just let do its thing. It's now about 8 sq meters in size!

It has about 6 or 7 pumpkins like this growing on it. I hope they're tasty!

Here's one of our capsicums

 In other news, some friends picked up this little toaster oven second hand ($10) and kindly passed it on to us. It's lovely, old, made in Japan (I'm guessing it's at least 40 years old) and has no electronics at all. It has a timer that uses a spring and rings a bell when its finished. Charming! It only uses a max of 750 W too, which is great. If I cover it with a couple of tea towels (and keep an eye on it, of course!), I can cook on quite a low setting. I've cooked lots of roast potatoes in it, and have also baked bread -- I want to try and pick up a small bread tin that will fit inside it. I cooked a loaf of bread using 0.2 kWh -- I'm pretty happy with that!