It’s been a while since I posted my method of making a wicking box and with some re-arranging of things on the deck, I found I had room for one more box there, making five in all. I’ve slightly varied the method so thought I’d go through it again.
The boxes I use are black plastic crates from Bunnings. I went for black rather than clear plastic, because algae will grow in wet soil when it can get light and I didn’t want ‘green’ sides to all my boxes. I thought the black colour would be an advantage in winter (warmer soil) but might not be so good in summer, though they could be easily shielded from the sun. They’re 60 cm long, 40 cm wide and 25 cm deep; not quite as deep as I would have liked at the time, although there are deeper ones available now, but useful for shallow-rooted plants which most vegetables are. When I started making wicking boxes I stocked up on the crates and bought a large number to store away for future use. This latest one will make 34 in service (I think there’s just one left under the house).
It’s usual, in large wicking beds anyway, to put in some form of perforated pipe across the bottom of the bed, which opens to the surface, through which to add water. The water spreads out to fill the reservoir below the bed and this is where the water comes from to wick up into the soil above. By looking down the pipe or using a dipstick, it’s possible to see if there is water in the reservoir or not.
For a small box like I was going to use, this is unnecessary; all I did was stand a piece of pipe in one corner of the box and drilled drainage holes (one at each end) about one-third of the way up from the bottom :
I soon found that adding water via the vertical pipe didn’t work, as it was just too slow a method to fill the lower part of the box (I get little frogs making a home in my pipes and they get pretty annoyed if I suddenly dump a load of water into the pipe). So I started watering overhead and have done so ever since. It’s what happens when it rains anyway. I use the pipe simply to check on water levels. If I can see water in the bottom of the pipe, I know the soil at the bottom of the box is saturated and I don’t need to water until I can’t see any water. The boxes will go several days more without water if the plants are small and not sucking much up. Poking a finger into the top few cm will show how moist the growing medium is.
I use home-made compost to fill the boxes. It’s made in a compost tumbler, using the litter and poo from under the perches in the chook coop and I bulk it out with mulched bracken, leaves and any other organic matter that becomes available. Note that I don’t have a water reservoir in the bottom of the box as some people do—my box is completely filled with compost and the bottom is simply saturated with water. Water-loving roots will grow into this layer and fine feeder roots will stick to the damper layer above.
Here’s the newest box on the deck, ready to go. The water in the bottom is from the recent rain—I don’t normally put the water in before I add the compost :
Usually I would just fill the box with compost, but it’s at a premium at the moment, because I’ve been using it to top up all my boxes in preparation for the coming growing season, so to save on compost (and get some extra organic matter into the box), I put a layer of sticks and bark in the bottom. They will rot down eventually. This was the variation from my usual method that I mentioned at the beginning :
I added the compost with some wood ash from the fire :
Topped off with a layer of bracken mulch and we’re ready to go :
I’ll probably plant a tomato at the rear and some climbing beans on either side to climb up the wire trellis I’ve put behind the box and maybe a cucumber or two in the front to scramble over the deck.
By the end of this growing season, it will all have settled down and I’ll top it up before the next crop goes in.
Here’s a line of 10 boxes I put in a few years ago :
I put them up on polystyrene fruit boxes to prevent rabbits accessing them. I’ve since found that a large rabbit can stand on its hind legs and nibble round the edges, so I’ve now put wire around the top of each box. Having them up off the ground means less bending and that’s good for my back.
Individual boxes can easily be covered to keep cabbage white butterflies out :
Sometimes its easier to direct-sow seed rather than go through the tedious process of sowing, potting up seedlings and transplanting. This is mizuna, an Asian green. I just clip off what I need with the scissors. The chooks get a handful every day and provided I cut above the growth point, it simply keeps on growing :
One important thing to remember about wicking boxes is not to over-fertilise. Added nutrients won’t leach away into the subsoil as they would in a normal garden, so what goes into the box stays there until taken up by the plants. I top up my boxes with compost when the level drops and once or twice during the season I’ll fill each plastic tube with worm juice or diluted seaweed fertiliser and let it absorb into the soil at the bottom of the box. It seems to work pretty well. I also add a few worms from the worm farm to help break down the compost.
Wicking boxes are the way to go for a water-saving garden. They suit small gardens, decks and courtyards. They’re easy to put together and provide a decent yield of a variety of food.