Toomas Karmo: Practical Horticulture: Self-Watering Pots with Bartholomew Mixture

Screenshot from one of my five (or so) Debian GNU/Linux 9.0 "Stable"-branch ("Stretch") GNOME desktops. Clockwise, from upper right: operations clocks (green for local civil time, red for UTC); four of my my five self-watering pots, in their metal bowls; two /usr/bin/xterm "glass teletype" windows, judiciously configured to display private casenotes on self-watering pots and on compost; my landlady's successful nasturtiums (a good plant, as I have learned in previous years, for self-watering pots in a sunny location; the leaves go well in a salad). - As always with such blogger uploads, the image can be enlarged in a normal Web browser by mouse-clicking.

Quality assessment:

On the 5-point scale current in Estonia, and surely in nearby nations, and familiar to observers of the academic arrangements of the late, unlamented, Union of Soviet Socialist Republics (applying the easy and lax standards Kmo deploys in his grubby imaginary "Aleksandr Stepanovitsh Popovi nimeline sangarliku raadio instituut" (the "Alexandr Stepanovitch Popov Institute of Heroic Radio") and his  grubby imaginary "Nikolai Ivanovitsh Lobatshevski nimeline sotsalitsliku matemaatika instituut" (the "Nicolai Ivanovich Lobachevsky Institute of Socialist Mathematics") - where, on the lax and easy grading philosophy of the twin Institutes, 1/5 is "epic fail", 2/5 is "failure not so disastrous as to be epic", 3/5 is "mediocre pass", 4/5 is "good", and 5/5 is "excellent"): 4/5. Justification: There was enough time to write out the  necessary points to reasonable length.


Revision history:

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• 20170816T0019Z/version 2.0.0: Kmo uploaded a polished version. He reserved the right to make minor, nonsubstantive, purely cosmetic, tweaks over the coming 48 hours, as here-undocumented versions 2.0.1, 2.0.2, 2.0.3, .. . 
• 20170815T0339Z/version 1.1.0: Kmo improved his outline somewhat. He realized he was now running behind schedule. He hoped to replace the outline with a short essay in coherent full-sentences prose, and to add graphics, by 20170815T1900Z or so.
• 20170815T0003Z/version 1.0.0: Kmo managed to post a semi-polished outline. He hoped to replace the outline with a short essay, in coherent full-sentences prose, at some point in the next 4 hours.

[CAUTION: A bug in the blogger server-side software has in some past months shown a propensity to insert inappropriate whitespace at some points in some of my posted essays. If a screen seems to end in empty space, keep scrolling down. The end of the posting is not reached until the usual blogger "Posted by Toomas (Tom) Karmo at" appears. - The blogger software has also shown a propensity, at any rate when coupled with my erstwhile, out-of-date, Web-authoring uploading browser, to generate HTML that gets formatted in different ways on different downloading browsers. Some downloading browsers have sometimes perhaps not correctly read in the entirety of the "Cascading Style Sheets"  (CSS) which on all ordinary Web servers control the browser placement of margins, sidebars, and the like. If you suspect CSS problems in your particular browser, be patient: it is probable that while some content has been shoved into some odd place (for instance, down to the bottom of your browser, where it ought to appear in the right-hand margin), all the server content has been pushed down into your browser in some place or other. - Finally, there may be blogger vagaries, outside my control, in font sizing or interlinear spacing or right-margin justification. - Anyone inclined to help with trouble-shooting, or to offer other kinds of technical advice, is welcome to write me via Toomas.Karmo@gmail.com.]

We all must do our part in greening the planet. As a minor blogging task this week (the major task, separate from this one, is precipitated by a sad thing, the death of observational astrophysicist Prof. Robert F. Garrison), I recount my experience with self-watering pots. 

On investigating self-watering planters on the Web three or so years ago, I came up with a design that proves perhaps excessively fancy, but has worked well for me. Plants are on this design rooted in around 10 cm of the Mel Bartholemew "Square Foot Garden" mixture, as explained at http://squarefootgardening.org/. The Mixture comprises equal parts (by volume) of vermiculite, peat moss, and compost. 

Bartholomew, the retired engineer who devised the recipe, recommends coarse-grade vermiculite.

Bartholomew particularly stresses that the compost has to be of high quality. Commercial compost may be of rather low quality, perhaps comprising the decayed remains of only one or two plant species. What is instead required is biodiversity in the decayed remains. One can solve the problem by composting kitchen waste at home, safe in the assurance that a typical kitchen generates waste of multiple kinds - potato peelings, wilted salad leaves, apple cores, eggshells, and much else. I, however, solved the problem through a piece of blind luck, unexpectedly getting earthworm droppings cheaply in the last, reduced-prices, hours of a "Canada Blooms" spring gardening show. It was a fairly good bet that the earthworms would have been fed properly biodiverse kitchen or restaurant waste, rather than the waste from some commercial monoculture farm.

The peat moss in Mr Bartholomew's list is a bit of an embarrassment, since mining the bogs for this not-easily-renewed resource impoverishes our biosphere. Perhaps some reader can someday find something better. 

[It is helpful to enlarge this graphic by mouse-clicking.]

The "Bartholomew Mixture" is marked "a" in my diagram. In my (perhaps needlessly fancy) design, the Mixture sits on an aluminium pie plate, "b", with a circular aperture cut into its centre, of radius just a little less than the radius of an aluminum beverage tin, such as is used for Coca-Cola, Seven-Up, and similar thirst-quenchers. (Useful graffito, from exactly 50 years ago this summer: "Visit Expo '67. Drink Canada Dry.") Under the pie plate is a beverage tin, "c" - with its top now cut open, and its sides now punctured. The 10-centimetre layer of Bartholemew Mixture, and the underlying pie plate, and the plate-supporting beverage tin sit inside a clay flowerpot, "d". The pot rests in turn on some pebbles, or pottery shards, or marbles, "e", at the bottom of a bowl "f". (Cheap ceramic or cheap plastic would serve. But I became rather fancy, buying brand-new bowls in some attractive metal like stainless steel.) 

Inside the beverage tin is a wick of some convenient absorbent material. I used kitchen sponges. However, old scraps of textile, or perhaps poor-grade soil of an intermediate particulate structure - not too rich in sand, and on the other hand not too rich in clay - are likely to provide equally effective wicking action.

The principle of operation is as follows: 

• Water is introduced to the bowl, to some convenient level "x" below the metal pie-plate "b". 
• Because the clay flowerpot is supported on the pebbles or shards or marbles "e", water is free to rise through the hole at the bottom of the pot, filling the pot to level "x". 
• Because the beverage tin is punctured, the water in the pot is free to enter the wicking material and to rise in the wick through capillary action to the wick-soil interface at "y". 
• Although the wick is liable to be soaking wet, the Bartholomew Mixture, "a", above "y" will take up only a reasonable quantity of water from the wick-soil interface at "y". The effect of this is that the Bartholomew Mixture will be damp, and yet will not be waterlogged. The roots of the plants will consequently avoid drowning - or, if they do have a little too much water, they will at any rate suffer this condition only in the immediate vicinity of the wick-soil interface at "y", with the higher strata of the soil drier.

Because the volume of water at the bottom of the assembly, below level "x", is large, approximating even the volume of the 10-centimetre Bartholomew Mixture layer between levels "y" and "z", the assembly will not need watering too often. I find in practice that when this assembly is brought indoors in the winter, into the Arizona-desert-like conditions a Canadian apartment develops from central heating, it is still not necessary to put water into the bowl more than once in six or seven days. 

 

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What to plant? Readers will have their own ideas. I have had excellent results outdoors in previous years with nasturtiums, and indoors with chives and a couple of other herbs.  In this season, I have chives (now two or more years old) in one of my five self-watering pots, and begonias in the others. 

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How should the design be simplified? Some successful work with tomatoes, on the sunny side of my previous landlord's house, suggests to me that it is enough to fill a large pot with a layer of some wicking material (with sponge or waste fabric - or more realistically and more cheaply, with poor-quality soil, neither too sandy nor too fine-grained), and to top this up with 10 or 20 or 30 centimetres of Bartholomew Mixture. The pot can then be set in some kind of water bath, in which the water never goes higher than the interface between the wicking material and the Bartholomew Mixture. The aluminium pie plate and the aluminium beverage tin now seem to me to be needless refinements. 

With the tomatoes, I actually filled the entire (huge, temporarily borrowed, almost tree-capable) pots with soil of agricultural quality, possibly - I am forgetting a detail here - a bit below the level of excellence of true Bartholomew Mixture. I then set the outsized pots into water in big plastic bins, such as are here in Canada sold at WalMart for organizing children's toys, winter clothes, and the like in a garage or storage closet. This must have meant that the soil close to the bottom of the pots became soaking wet, and deficient in oxygen, and that the soil above the water line in the bins became damp without being waterlogged. I imagine the tomato-plant roots simply pushing down until they encountered the waterlogged layer, and realizing in their mute way that with oxygen now absent, there was no point in pushing lower. At any rate the green stems and leaves gazed up at me cheerfully enough, uttering not one syllable of complaint in all their vigorous growing, and in the late summer bearing a reasonably abundant harvest.

[This is the end of the current blog posting.]