I use galvanized water troughs as raised planters in my vegetable gardens because the big containers look great, offer plenty of planting space, and will last for years. As a bonus, their soil warms up faster than adjacent in ground beds, which means that warm season crops like tomatoes and eggplants love to call the troughs home. Converting a trough into a planter is easy and takes less than an hour.
You can find the troughs, which are also called livestock tanks, at feed stores, though I've noticed some well-stocked nurseries are also starting to carry them. The tanks aren't cheap--they typically run between $115 and $175 depending on the size--but building a similarly sized raised bed out of cedar would cost a comparable amount and the tanks have the advantage of being rot-proof.
The tanks are made to hold water, which is a situation you'll need to remedy before you can use them as a planter. Good drainage is super important in containers, so you'll want to drill or hammer holes all over the bottom of the container. We've made holes two ways: with a drill or with a metal stake and a heavy hammer. If using a drill, be sure to fit it with a drill bit made to bore through metal. If using a metal stake, we have found it easier to hammer through the bottom if the tank is right side up (i.e. with its mouth facing up).
Position the tanks where you would like them to be in the garden. Then, stand back and take a good look before filling them with soil. Make sure the seam is at the back and that the tanks are level. The least expensive option for filling the tanks with soil is to purchase bulk topsoil. Most topsoil suppliers have a "vegetable garden mix" that contains topsoil, sand, and compost. Some people advocate putting soda cans in the bottom 1/4 of the tank to reduce the amount of top soil required to fill them up. But, I think it is best to fill the tanks up completely with soil, because this gives you the option of planting deeply rooted plants, like dwarf fruit trees or raspberries. Fill the container with soil until it is nearly level with the rim, as the soil will settle quite a bit once you water. I plant lobelia, nasturtiums and bidens around the bottom of my tanks to soften up their edges and help them blend into the rest of the garden.
Note: Prior to putting the troughs into my garden I did quite a bit of research regarding the possibility of zinc leaching into the soil. I determined that the likelihood is low, because I maintain a fairly neutral soil pH in my beds. So far I have seen no signs of zinc toxicity and I am not concerned about it.
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Willi Galloway writes The Gardener column. She lives in Portland, Oregon and writes about her kitchen garden on her blog DigginFood. Her first book Grow. Cook. Eat. A Food-Lovers Guide To Kitchen Gardening will be published in January 2012.
(Images: All images by Willi Galloway)