Another garden problem, and rediscovering preexisting wisdom: I had read in various gardening advice works** that one should not water at night to prevent mould/fungus growth on the leaves.
I ignored this, and water often at night. Over the last three month, I've got fungus on the otherwise-thriving pots of sugar-snap sweet peas, which are in a row, elevated, about 6 in. height x 4 in. diameter black pots.
I also grow pretty intensively in these pots, as elsewhere, and have generally the following sorts of things in each pot: kale, sweet pea, bok choi, carrots, feral basil, feral mint, garlic shoots etc. Very concentrated-planted pots, with everything planted together.
(I should write something on garden design, or non-design in my case - there are no real rows and minimal species partitioning. Partly I want a food forest effect, partly I want concentration, partly I have so little space I want to put in as much as possible in the small space).
Anyway, relevant point is that I water using a watering can with a shower-head style-head, and this mould is only appearing on the sweet peas, among all the other vegetables in each pot.
So I thought: for these established pots, I need to move to a watering head that is flow and not shower-sprinkle, and wet the ground of the pots, and miss the foliage.
I seem to have solved it by drilling holes in a scavenged champagne cork, which I put on the nozzle. Cheap, easy and effective, and another consumer item I didn't have to buy.
After a bit of experimenting, I found that cork doesn't like little holes all that much.
I started with a 2.7 mm drill piece drilling four holes, and got mediocre results. I then drilled one single hole through them with a 5.5 mm bit. This seemed to work well, when I tested it.
If one was going to drill only one hole to start, I'd use a 6 or a 6.6 mm. I think that a normal champagne cork would probably tolerate 1-3 6 mm-bit holes.
Remember that it is seriously contracted when put into the nozzle. So a 6 mm hole ends up with a flow like what you might expect for a 3-4 mm hole.
So - next time I won't walk past an abandoned cork on the street.
** For example, this issue is addressed in Jackie French's informative-enough but tonally-cloying and somewhat rural hippyish Natural Control of Garden Pests, 2nd ed.; Melbourne: Arid, 2002, ISBN 9780 947214555. I can't recall what exactly she advises on the issue, and I can't seem to find it on the shelf at the moment. Despite its style issues, I'd recommend this book - grit your teeth and mine it for tips once, then consult as a reference work--if you can find it again.
(I wonder where the corks really came from--Rick.)
Attribution of image:
By Libation U.N. Limited (Champagne Resources - Libation U.N. Limited) [GFDL or CC-BY-SA-3.0], via Wikimedia Commons