The setup, and what's wrong with watering

Finally!

Last night I planted my first flat of flowers. I had an hour or so to go downstairs and since the glue had dried sealing the leak of last week it was finally time to plant. Tragically, my watering system still has problems and until I figure out how to fix it I'll have to abandon automatic watering and try to keep on top of my plants' watering needs the old fashioned way.

Let me explain my seed starting setup, with pictures to come. I built a 4' x 4' table. On the table I've got a heat mat, with a thermostat, which heats up the flats to a temperature suited to germination (about 70 degrees). A flat, incidentally, is an industry standard--a 10" x 20" plastic tray, often used to hold compartmentalized seedling trays. I bought a bunch of the trays, with different numbers of compartments of varying size (see product picture for size comparison). On top of the heat mat, and under the seed trays, I've got a capillary mat, which uses osmosis to water the seed trays from below. I can't seem to find the exact mat I bought on the Charleys site. Mine came with a plastic sheet to go underneath (to keep water off the heat mat) and a fabric sheet to cover the capillary mat and keep errant plant roots from growing down into the mat.

I intended to provide water to the capillary mat from a piece of plastic rain gutter which I cut to size and capped on the ends. It's the caps that were leaking previously--all fixed now. I feed water to the gutter via a small water pump that pumps water from a plastic Rubbermaid-type tub under the table. The tube from the water pump connects to a small adapter I glued into one of the gutter end-caps. On the other end-cap there's another adapter with a tube that drains back into the tub. In this way the gutter can be kept full as long as the tub continues to have enough water to feed the pump. I figured every day or two I could dump a pitcher of water in and I'd be good.

The watering problem I had last week was that I had the gutter (about 4" high) setting on top of the table with the capillary mat end placed in such a way as to hang a few inches into the water in the gutter. While I had tested this arrangement successfully before I let it run a little longer this time and it quickly became clear that water was spilling off the mat and making a mess. My theory is this: The mat was effectively pulling water out of the tray--osmosis was working. But as the water moved out of the tray and dropped the 4" to the table it sucked more water behind it--a siphoning action. Osmosis + siphoning = too much water. The solution was to add brackets to the table to allow the gutter to sit at table height rather than above it. In this fashion siphoning wouldn't really work (siphoning requiring gravity and gravity requiring a height differential) and I'd be back to just osmosis. At this point I moved everything around and caused the leak in the end-cap so I fixed the leak, which brings us to last night.

Last night I discovered my drain wasn't reliable. My gutter filled with water as the little pump did its business. Sadly, though, while the drain could go for a good 20 minutes or so successfully I noticed on two occasions water spilling over the lip of the gutter. I had no choice but to flip off the pump, which meant my capillary mat no longer had a water supply. So what now, a bigger drain tube? I don't know yet. I just know I'm out of time and have to plant seeds. And that brings me to the next post, which will concern what I planted.