installing a wicking garden

So we've had a goal to install a wicking garden, and with spring having sprung, now is the time! Thankfully the predicted rains didn't materialize this weekend so we had two solid days to get wicking.

We've written about wicking gardens before, but this is the first time we've built one. We decided to use two-foot deep stock tanks (all round) for our garden.

chose your water-proof container

First, we went to the place of the stock tanks (and goats and chickens, and little pigs) to learn about what sizes and styles were available and at what cost:

Bingo! Good looking tanks with horizontal banding (yuh-huh...) and fairly reasonable pricing.

decide where to put your container

We then worked on placement and sizes (see green circles below):

Having decided what and where, we rented a trailer yesterday at 3 pm and picked up our four stock tanks: one 6-footer, one 5-footer, one 4-footer, and one 3-footer. Having decreasing sizes helped in transporting them since they each snugged in with their bigger sisters.

Using stock tanks is awesome for several reasons:

(1) There ain't no digging.
(2) There ain't no building.
(3) There ain't no bending over when gardening.
(3) And, it turns out, the 2-foot depth of the ones we chose are perfect for wicking.

Wicking beds work via capillary action, the physical force that allows water to moves upwards into, say, a paper towel. According to the experts, your storage media (more on that in a bit) should not be deeper than 30 centimeters (11.8 inches) and your soil layer should not be deeper than 30 centimeters (11.8 inches). With a 2-foot deep stock tank, you have the perfect depth (we decreased our thicknesses to 9 inches to allow space for compost and rain capture).

install drainage tubing and standpipe

After placing the tanks, we used drainage tubing to line the perimeter of the tank connected to itself with a T fitting. This allows the water, when added, to get to all parts of the tank and to provide storage for water.

This tubing has little slots in it to let water out:

Into the top of the T fitting we placed a 2-foot long piece of solid wall drainage pipe:

The T-fitting isn't made for the solid wall drainpipe, so we stuffed some weed guard into the annulus around the pipe and duct-taped it all together. It's not important to have a water-tight seal here; however, it's a good idea to keep the storage media (the gravel) out of the pipe (although even that's not fatal!).

put in some gravel

Once we had that done, the next step was to fill the tank with nine inches of gravel. The gravel we used is the landscaping gravel we dug out to install the rainwater harvesting tank, so it was perfect to have it available and on site (and it turned out we had just enough: perfect!). Finer grained gravel is better than coarse gravel because the magic of capillarity is stronger in finer grained stuff. Furthermore, poorly sorted gravel (gravel with various sized bits in it) is better than well sorted gravel (all the same size). Again, capillarity is better in poorly sorted stuff. If we hadn't had this gravel on hand, we would have gotten crushed glass (recycled! free!) from the City of Austin instead.

install an overflow drain

The next step was installing an overflow drain. The overflow drain keeps the tank from completely filling and drowning the plants. For the drain, we used 3/4-inch PVC with a 1-inch outer diameter set just above the top of the gravel. This, it turns out, was the most challenging part of the project since there ain't many 1-inch drill bits out there. I found one, but it would't fit our drill, so I wound up using a masonry bit I had. It was ugly, but it did the job:

install landscaping fabric

After that, we put down landscaping fabric to allow water to transfer between the gravel and soil (and vice-versa if needed) and to keep the soil from "leaking" into the gravel below. 

place some soil

Next step was putting in 9 inches of soil:

plant some stuff

Next up was planting! We planted several peppers in the small tank along with several marigolds (purported to be natural pest repellant). We then topped the topsoil off with a few inches of compost.

fill 'er up!

We then filled the tank with rainwater until the overflow flowed:

instant self-watering garden!

And there you have it! All we have to do now is to top off the tanks once a week and watch the plants grow. Yes, we'll have to water the plants until they get roots down a little deeper, but after that we should have a water efficient and lower maintenance garden. 

We got all four tanks installed except for soil in the one (cause we could't wait...) in about six hours. Not bad. 

Some references on building wicking gardens:

A great article at Resilience.

Article at Instructables about putting one in here in Austin.

Article at Urban Food Garden.

Status updates...



  1. Neat! And these pictures remind me how long it's been since we've been over there. We've never even seen your rainwater tank!

    1. yeah! we need to have y'all over! have been ashamed (always on porch lights, unpainted walls...)

  2. This looks legit. I'm going to squirrel away this method for when my small raised beds croak on me.