Growing food in containers can be useful for so many situations– it’s quick to set up and can utilize very small outdoor spaces. Since it requires no commitment to a piece of ground, it’s renter friendly. Because growing in containers is so approachable, it’s where many people start gardening. Unfortunately, although the setup is undeniably quick and easy (albeit expensive) actually getting food plants to grow and produce in containers is often much more challenging than in the ground.
Perhaps the biggest problem for container growing is inconsistent moisture– while herbs and some flowers do fine with the occasional droughts, food plants often never recover from even short gaps in watering. When you’ve planted into the ground, once your plants get a good root system established there’s almost always a little moisture down under there, but a containers can go really and truly dry in not very much time at all. Unless you live in a cool damp place, and are a good every-day-without-fail waterer (very much not me!) you are likely to hit some trouble.
This is partly because of the other reason food in pots can fail– almost every garden pot sold is much too small. In addition to not providing enough root space for any food crops except lettuce, spinach and radishes (not coincidentally the three crops most sensitive to dry soil), a small amount of dirt is considerably more prone to drying out, especially if it’s in a terra cotta pot. Those suckers ought not to be allowed in sizes smaller than 12 inch. I’ve even managed to kill plants in small pots in Cordova, the cold northern end of the temperate rainforest! When something dies from lack of water in Cordova, it is truly impressive.
Ever since I read about self irrigating planters (SIPs) on Root Simple years ago, I have been fascinated by them. The idea behind SIPs is to use a large container such as a rubbermaid tote, create a water resevoir in the bottom and some form of a wick up into a peat-heavy potting soil. When you water, you fill the resevoir, and it slowly wicks up into the soil providing consistently perfect moisture for your plants. I am a sucker for simple technology, particularly when it repurposes trash, and loved the quiet brilliance of this design.
At home in Cordova I had no reason to build a SIP, I had all the ground-based growing space I could manage. So I was excited when we moved to a rental house in New Orleans and I finally had a good excuse to give it a try. Shortly after our move, with a toddler helping and newborn fussing, I made three SIPs out of rubbermaid totes.
Of course, I don’t like to do anything the regular way, even the regular alternative way, so I made some adjustments to the classic SIP design. I’m not sure if my adjustments are an improvement, but it does make the design more accesible.
The classic design uses upright sections of PVC with holes drilled in them to hold up the divider between resevoir and soil, as well as a “pond basket” to hold the wick of pure peat moss. I didn’t want to have to drive all the way to Lowe’s to buy PVC and a pond basket. Even though these items are cheap, I had some kind of mental block against buying them, which for a few months prevented me from tackling the project at all. Do you do this? I knew I was being ridiculous, losing months of good growing weather, but I couldn’t get over the idea that I ought to be able to scrounge good substitutes.
Eventually I hit on a slightly different idea. Lots of materials wick water, couldn’t I use some kind of old cotton cloth? Like these old sheets, cut and braided into a fat wick?
And why did the resevoir need to be integral? Could I use something else, put into the tote, like…. an old milk jug?
So was born my super simple scrounge SIPs. I bet you have the materials on hand to make one of these right now!
- one rubbermaid or similar large tote, not clear (or algae will grow)
- two old gallon milk jugs, scrubbed scruppulously clean and bleached (if you can find water jugs in someone’s recycling you can skip the scrubbing and sterilizing)
- two small (12 oz) drink bottles
- one old bath towel or cotton sheet
- razor blade or very sharp knife
With the traditional SIP design, you need the tote to be free of holes or cracks, but for this design, because the resevoir is in the jugs, you can use any old tote off the side of the road, so long as it’s sturdy enough to fill with soil. In fact, it needs to be able to drain so that rain doesn’t pool up in it. So, start by drilling a dozen or so holes in the bottom, or if you don’t have a drill, punch holes with a nail.
Cut your towel in half lengthwise, trim to about 2 and 1/2 feet long, and roll into a tight log. Squeeze your hand around the roll and try to estimate the size, then cut a similar sized round hole into the top of your milk jug. Cut it smaller than you think, you can always cut a bit more. You want the towel to fill the hole completely so that dirt doesn’t fall in. Work one end of the towel roll through the hole (a butter knife might help) and all the way to the bottom of the jug. Repeat with your other jug. [If you are using an old sheet, cut in half widthwise, then cut each half into three pieces. Braid them together and rubberband the ends to secure.]
Set the jugs into the tote at opposite ends of the same side, and flop the towel ends over the edge of the container. Cut the bottoms off of the small drink bottles, and invert, setting the mouth into the mouth of the milk jugs. These will be where you stick the hose to fill the resevoir jugs.
If you have access to top quality potting mix you can use it straight up, but if all you can find is that crap with sticks and chunks in it, mix with an equal quantity of good, finished compost or if you’re really desperate, peat moss and organic fertilizer. The mix needs to have a large proportion of fine organic material in order to wick the water around. Add in some perlite or vermiculite if you have it.
Pour soil mix in around the jugs, tamping down firmly as you go. When the dirt is even with the wicks (make sure it’s well tamped), lay them down on the surface. Being careful to keep the drink bottles in place, continue filling with dirt right up to the rim of the tote, it will settle a bit over the next few weeks.
Fill jugs by sticking hose into the inverted drink bottles, when the water level rises into the top bottle, it means the jug is full. Since it’s not a tight seal, extra water will leak out where the two mouths meet, but it doesn’t matter. Soak the soil itself thoroughly and then plant.
The classic SIP technique is to sprinkle fertilizer on the soil surface and then cover the whole thing with plastic mulch. You cut the middle out of the lid to make a rim, then just cover the tote with a black plastic bag (white if you live in a hot climate), snap on rim, and cut holes for your plants.
I never got around to doing this though, I just couldn’t get over cutting the soil off from the world to such a complete degree. The top plastic would keep a lot of moisture in, keep weeds from growing, and allow the top-dressing of fertilizer to absorb slowly. But plastic on all sides? Couldn’t do it. Instead I mulched my totes with a thick layer of leaves, just like I do in the garden. Worked great, but then our climate is very damp.
Which brings us to the question of outcome. How did my alternative SIP design work?
Well, it worked just fine, I only needed to water once every few days, and the soil stayed very moist. Plants grew large and healthy, and produced as well as those in the ground. But, given our incredibly damp climate (summer is downright wet) I was not entirely convinced that plain old totes would not have done the job perfectly well on their own. They hold such a large amount of soil that it even when I got lazy and forgot to water for days on end, the soil stayed reasonably moist 6 inches down and the plants seemed fine.
I grew out 3 seasons of plants before I dumped the soil out to refill with fresh stuff (I needed organic material for my dirt garden, if I hadn’t I would have added in a good quantity of compost and fertilizer and kept going with the same stuff for a few more seasons). When I dumped it out, I discovered that the wicks had almost completely disappeared. Oh! Of course! Cotton + consistent moisture + heat = compost. Whoops.
To be honest, I didn’t re-make them as SIPs. I just filled them up to use as regular, very large planters. I planted salad greens, who’s shallow roots are very sensitive to lapses in water, and so far they’re doing beautifully.
I’m still a fan of SIPs though. If you live in a dry place, or go out of town often, and want to give them a try, this super easy set-up has the advantage of immediacy. No complicated trips to the store, which can put a mama with kiddos back for months. No fancy tools. No questionable PVC. Almost no money outlay at all if you’ve got an old tote around, though you still have to buy potting mix. The wicks lasted at least a solid year, and replacing them every spring wouldn’t be hard.
Even easier though? Skip the stupidly small and infuriatingly shallow (but darn aren’t they pretty) regular garden pots and plant vegetables in a plain old large plastic tote with drainage holes. If you live in a damp climate, this will probably be enough to make the difference.
Just don’t tell your neighbors it was my idea.