DIY: Make a Self-Watering Planter

Whether you live in a four-season climate or a small apartment in the city, fresh food at your fingertips is easier than you think! Just follow the directions for this self-watering growing container and you’ll have an abundance of produce in no time.

The following is an excerpt from Fresh Food From Small Spaces by R. J. Ruppenthal. It has been adapted for the web.

If you are on a bootstrap budget, you can make a self-watering growing container yourself. I have made several of my own, using Rubbermaid or Sterilite storage containers, that grew some mighty fine vegetables. If you have a couple of extra 5-gallon plastic buckets, or a metal or plastic washtub, you could modify any of these as well. All you need is the container plus a few materials, which can be purchased for around $10 at your local hardware store or garden center. If you are buying a container, then the darker plastic colors are best because they hold in the heat well (unless too much heat is a problem in your climate, in which case you should go with white). Most hardware stores, drugstores, or home centers stock some of the large, featureless plastic basins or storage containers that work best for this project.

The basic design of self-watering containers is that they have a water reservoir below the growing chamber. These two chambers are separated by a rack of some sort, which holds most of the soil above the water. This separating rack can be made from the top of a Rubbermaid or Sterilite container box that is cut to fit inside, or else you could use two containers, drill holes in the bottom of one, and nest that inside the other.

The water reservoir does not need to be as tall as the growing chamber, perhaps one-fourth to one-third as tall. You then need to put a larger hole or two in this rack for one or more “soil feet,” which will sit in the water, holding a small amount of soil that wicks up the moisture into the main soil and toward the plant’s roots. To hold the “soil feet” in the water, a basket of some sort can be inserted there and then packed with soil for each of the soil “feet.” A snack tray or pond basket can do the trick, or you could even use an old coffee can, plastic nursery pot, or 2-liter soda bottle base that is cut to fit and then punctured with holes.

The very top of the soil may dry out, but what’s really important is that there is lightly moist soil about 5 or 6 inches down. You can keep adding water right up until it starts spilling out of the drainage hole, meaning that it has reached full capacity at the height of the soil rack.

Next, you should decide whether to mulch. Spreading some mulch on top of the soil preserves moisture and keeps the plants a bit warmer. If you decide to use black plastic sheeting as mulch, then first do the fertilizing as described below. Then cover with plastic mulch, which can be duct-taped to the sides or held down with the cutout frame of your container’s top if there is one. Cut an “x” in the black plastic wherever you want to put a plant. Whether or not you have mulched with black plastic, go ahead and plant your veggies next. Give each plant adequate root spacing according to the recommendations for that type of seed or transplant.

Once they are planted, if you have not yet fertilized, then side-dress the plants with a line or two of fertilizer along the top of the soil. Try to place this band a few inches from the plant stems, which will encourage better root growth. For most organic fertilizer, 2 to 3 cups per 2 cubic feet of soil is enough. (This is the Earthbox capacity.)

Finally, if you have not used black plastic, then you could now add any other kind of mulch: sawdust, grass clippings, leaves, etc. After the growing season, take out the old plants and try to remove the worst of their roots. Then scrape off any remaining fertilizer (or the first two inches of soil), top off with new soil mix, and then add your new plants and a fertilizer band as before. Every day or two, add water into the pipe or tube until the reservoir is topped off. You should be all set!

One caveat with self-watering planters: The size of the “soil foot” that sits in the water determines how wet your soil will be. If the soil foot is relatively wide (covering more than about 20 percent, horizontally, of the bottom area of the container), your soil will be quite moist. If you want to grow root or tuber vegetables in this container, such as carrots or potatoes, wetter soil can mean more disease problems, so you may need to use a narrower item for the soil foot to sit in. Root crops may also taste better if they are forced to grow downward toward the water. Here are three possible solutions to keep your soil a bit drier, any one of which should help:

1. When you are making the self-watering box, limit the size of the soil foot, so that it covers no more than about 10 to 15 percent of the base. This will allow less water up into the soil and allow for healthy root crops.

2. Add a little more sand to your soil, which should limit the wicking action of its organic material.

3. Allow the water in the reservoir to be completely used up before watering again, and do not give it more than one day’s worth of water at a time. Advocates of a wet-dry growing cycle also can follow this suggestion, though in my experience, a self-watering container will grow healthy vegetables of all kinds without any special care.

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