sub-irrigation

Reading around the garden blogs I have made a discovery: sub-irrigation. It's simply a method where a plant is in a container that sits inside another one which holds water, and a wick allows capillary action to move the water from the reservoir up to the plant's roots. There's quite a number of do-it-yourself recycle-materials projects out there, from using five-gallon buckets to cutting up plastic beverage bottles. And then of course you can buy ready-made planters which look quite nice.

I'm attracted to this for several reasons. Supposedly it uses a lot less water. If you keep the water from ever reaching the top inch of soil, you don't get gnats (which plague my houseplants every summer). The planters outside never get invaded by weeds. You can grow anywhere that has sun- rooftop, patio, balcony, etc. So if I ever end up living in a place with no backyard to garden in, I'll probably try this.

I did have some questions about it all. Such as: what keeps the roots from rotting, if the soil is always drawing up moisture? Turns out you have to poke air-holes in the bottom of the top planter-part, and have an overflow in the reservoir part, to keep the water level from getting too high. And of course I assume you still have to check on the plant and make sure it dries out a bit before you refill the reservoir.

Something about it all feels weird to me, though. I picture an entire container garden with its growing medium covered in black plastic, and it feels wrong that rainfall isn't watering those plants. Also strange would be to have a garden without worms and compost in the soil. But I was still intrigued enough that I wanted to try it for myself, if only on a small scale.

First off, I thought I'd just try sub-watering some of my Tomato seedlings and see how they do. So I picked half to get watered from below, and half from above. The Cherry Tomatoes are in deeper trays so I watered those from below.

The B and B (beefsteak and brandywine) seedlings are in shallow drip trays, so those I'll still water from above. We'll see if they grow at different rates, or if one uses less water than the other...

Of course my main concern with the sub-irrigated ones is that the cardboard will get moldy. But by that time I'll have proved to myself if this method is all it's hyped up to be, and the plants will be ready for bigger pots anyway.