Water retention in container gardening

Welcome Juliet! I currently live in a condo after losing my home and beautiful organic garden years ago in the economic downturn. I now have to garden in containers only and I have to make sure that I don't offend the HOA. I mostly use the big black plastic pots that nursery trees/bushes come in. I have two challenges with container gardening. The first is the ability to add enough organic materials every year to sustain the soil without overflowing the pots. Generally I have to take some dirt out to make room, which makes it hard to create a permaculture pot, if you know what I mean. How do you recommend augmenting the soil with organic material without overwhelming the pots? The second issue has to do with retaining moisture in the pots without constant watering because of the black plastic heating up in the sun, drying out the soil faster. Do you have a recommendation for an ascetically pleasing coating or that won't offend the HOA gods and yet will possibly help me manage my water better? The overwatering is not good for many of my plants and yet they will become over-stressed without it. How do you overcome this with container gardening? Thanks, I look forward to your response!

A few years ago I made self watering pots.
Start with an acceptably aesthetic pot that is water tight. I found these plastic half- barrel things for cheap.
1. Cut a disk of some material to sit at the right height. I used a plastic barrel lid. If you aren't too fussy about the looks you can use a plastic 55 gal barrel for the entire project.(cut the thick rim off the top, then cut in half, the top will slide inside the bottom http://i828.photobucket.com/albums/zz206/Indyyeti/garden/010.jpg )
My measurements for using a 55 gal barrel - http://i828.photobucket.com/albums/zz206/Indyyeti/garden/012.jpg

2. Cut some supports to hold your disk at the correct height. I used 3" PVC pipe with a few holes drilled so they'll fill and drain easily.

3. Make holes in your disk for the wicking mat fabric and the fill tube.

4. Set your disk on the supports inside the pot, lay in some landscape cloth(so the soil doesn't drain into the water reservoir ) then cut small holes to feed the wicking fabric through. I cut the fabric at the ends to spread it out and wrapped it around the fill tube. http://i828.photobucket.com/albums/zz206/Indyyeti/garden/015-1.jpg

5. Start filling with soil, spreading the wicking fabric evenly throughout the soil as you go.

6. Don't forget to drill an overflow hole!!!

7. I used inch and a quarter PVC for the fill tube and cut a long bit of styrofoam to fit inside as a water gauge. If there's any water at all in the bottom the styro floats and raises up the tube letting you judge when to refill.

Thanks Roy - nice setup!

My slightly easier, slightly less attractive set up is to use a big bottle of water for each pot; I generally use wine bottles, but 2 liter plastic bottles are fine too. I fill them up, then turn them upside down quickly and poke them into the soil of the pot so the mouth of the bottle is pushed an inch or two down. That soil contact forms a sort of cork, so the water is absorbed by the soil very slowly; I generally have to fill up the bottles every couple of days, and the plants really respond to having a constant water supply, rather than the flood/drought that hand watering provides. Also, it's just a lot less work than hand watering, and saves on water. But as I mentioned, it's not very pretty!

Hi Steve! Roy and Galadriel have already mentioned two of the things I was going to suggest -- self-watering containers, and some form of slow-watering solution. (Though, Galadriel, I tried your method a couple of years ago and found that the 'corking' effect didn't really work for me and the whole lot drained out pretty fast. Did you have any thoughts on that? It might have been a soil problem; that particular container had quite poor soil.)

Another slow-watering option if you have large containers is a variation on an idea which I think originates in parts of Africa but I picked up from Permaculture Magazine: bury a porous (e.g. ceramic) pot in the soil, with an inch or so above soil level to keep the soil out of it. If it has a drainage hole in the bottom you'll want to stick a cork or similar in it. Fill it with water and it will gradually leak out into the surrounding soil. Ideally you should cover it with something to prevent direct evaporation but I haven't yet constructed anything suitable and I found that it worked OK anyway. I've used that method in raised beds and in a biggish container, but in the container I could only fit quite a small pot so it's not a perfect solution.

You can also mulch to reduce water evaporation from the soil, if you aren't already. But yeah, the bottom line is that watering is a problem for container gardens and self-watering containers are the closest to a solution I've found. If it helps, ceramic pots lose water several times faster! (I find this annoying; I prefer ceramic as a material but it's much less practical.)

No idea if this would work, or offend your HOA, but could you paint your containers white to reduce the soil-warming effect?


Onto your other question, of soil. I'm afraid I don't have a solution there, either; I don't think it's possible to truly create a 'permaculture pot' in the same way that you can create 'permaculture soil' in a regular-sized garden. In my experience the soil in a pot does shrink a bit over time, but not enough to make enough space to really replenish the organic material.

With big pots you can (depending on conditions) start to get a bit of soil life going in there, especially if you're making your own compost -- I've found happy worms in big pots on hard surfaces and assume they must have come in with the compost!

With perennials I try to top up as much as possible, take a bit out at the sides if I have to to make more space, and use compost tea as an occasional feed. With annuals, I turf the whole lot out when the pot is empty, mix it up with nice new stuff, and shove it all back in again. These days my container gardening is in the context of a (tiny) 'proper' garden and I do sometimes just chuck really manky potting compost into the compost pile as a way of mixing it up. NB I am aware that annuals aren't very 'permaculture' but I am a strong proponent of growing things that you love and will eat, and sometimes annuals do tick that box. Tomatoes, courgettes, and broad beans, for me personally, are worth growing even as annuals; and tomatoes do very well in containers which is handy!

Juliet Kemp wrote:Though, Galadriel, I tried your method a couple of years ago and found that the 'corking' effect didn't really work for me and the whole lot drained out pretty fast. Did you have any thoughts on that? It might have been a soil problem; that particular container had quite poor soil.)

I think the potting soil has to have a fair amount of organic material. I also find that if the bottle isn't stuck in deep enough, it does just leak out instead of wicking out slowly. I admit it's not a perfect solution, but much preferable to my previous method of hand watering--which I sometimes had to do up to three times a day--and I live in rainy Yorkshire

Thanks Galadriel and Juliet. Although I am sure it would work, the bottle-solution probably would be frowned upon by the HOA - too cluttered looking. I already am pushing it with the containers as it is since they weren't supposed to be between the buildings (which they are) so they might not like the appearance, but it is worth trying on a small scale and seeing what they say. And Juliet, the design you were talking about is somewhat of a take-off of the desert refrigerator/swamp cooler which might not only have the watering effect but a cooling effect in the middle of the summer. Interesting! And after posting my question, I was thinking about painting one side (only) white or with the RV reflective paint and facing the black side towards the sun during the early and late season, and then turning the white towards the sun during the mid-summer. The pots are situated against the condo wall and side by side, so it's not like the different colors would be blatantly obvious, if you know what I mean.

Thanks again for the ideas!

You can get pretty looking glass things that fulfil the same function as the upturned wine bottles, usually called 'aqua globes' or 'watering bulbs'- don't usually hold quite as much water as a wine bottle and obviously aren't plucked from the waste stream, but your HOA may like that kind of thing more? You get them in all kinds of multicolours, and bird-shaped ones and things.

And with pots, could you cover them? Think covering them in bubble wrap and tin foil or something (to reflect heat/light off or even insulate from the heat), then cover in burlap with a ribbon tied at the top, or some other aesthetically 'pleasing' kind of thing you tend to see in daft interior design magazines? In the same vein could you build wooden planter-holders from old pallets or something, call it 'vintage', then you can put your pots inside- possibly filling the gaps with Styrofoam or whatever to give you some protection from the heat? (Though if you're building big wooden planter-holders you might as well build self-watering ones!)

Ooh, I like the different sides of paint idea! I guess that wouldn't work if you were 'stacking' the plants in the containers though. (I've sometimes grown a tall thing at the back of a container against the wall and short things in front.)

Thanks Galadriel -- I might give that another go this summer as I too hate repeated daily watering.

You are both right. Nicer glass containers might be acceptable and turning tall items might be problematic. Then again, peas might be grown early in the season (black out) and then be finished when it is time to turn the container (white out) and plant new sun-loving varieties. Or just plant the plants that don't like the intense sun (ie - lettuce) in the now-shadow section, allowing the sun-living ones upfront to take the brunt of the sun and extending my cool season growing crops!

Hi there,

I purchased an automatic sprinkler system, that lets you add as many little feeder tubes off the main hose as I had pots, and more if I add more pots. I used the one from Gardenia: http://www.gardena.com/uk/water-management/micro-drip-irrigation-system/ It is a micro-irrigation system and lets you feed very little amounts of water directly to the root of your plants, minimising water use. Also, drippers can be adjusted to release more or less water, depending on the needs of the plants, and season. Finally, a timer lets you adjust how many minutes a day you want to let the system run, so you can again adjust it for the season.

In addition, I found that using effective microorganisms (developed by Dr. Teruo Higa from Japan) is a natural and incredibly efficient way to get good soil organisms into your pots, and over time, these organisms help keep your soil alive and water absorbent. I discovered it takes a few years of using EM to really see the result, but then it suddenly became an exponential wow effect...just like all the books describe.

You can also add some biochar into your potting soil, if you spray it with EM1 before mixing it in, it helps the effective micro organisms develop faster, as well as adding soil carbon. The microbes also sequester carbon from the atmosphere into the soil, so that helps too.

What I would like to know, if there is a layering technique that could be used in pots, similar to the ones used in Hügelkultur or Raised Beds, that would help also?

Best, Diana