I am so completely sold on the benefits of self-watering (also known as sub-irrigated) planters!
Here are some parsley plants I grew from seed. The ones planted in the sub-irrigated planters are much larger, have much larger leaves, and much thicker stems than the seedlings growing in the standard cup planters.
I make my own sub-irrigated planters from 2- or 3-liter soft drink bottles. Here is how you can make your own as well:
Using a drill or soldering iron, make 2 or 3 holes around the neck of the bottle to aid in water absorption.
To prevent over-watering from rain or sprinklers (in case these will be outside), make 1 or 2 holes around the top curve of the bottle so that excess water can drain into the water reservoir, if necessary.
Cut off the bottom third of the bottle.
This will become the water reservoir.
Cut a circle of polypropylene fabric such as that from a reusable shopping bag. (My bag was from Wal-Mart and cost $0.50.) This fabric won't rot and will allow the water to wick up into the soil.
Fasten the fabric securely to the neck of the bottle using a zip tie or something similar. This will hold the potting mix in the bottle, and prevent the plant’s roots from growing down into the water.
Pack soil-less potting mix or peat moss firmly down into the tip of the bottle. Plain dirt or potting soil will not allow the water to wick up to the plants’ roots, so soil-less potting mix or peat moss is best.
Fill the bottle the rest of the way with potting mix and moisten thoroughly. (Stir the potting mix to make sure it is completely moistened.) There should be some water that drips down into the water reservoir.
Make a well in the center of the potting mix and insert your plant. Top with more potting mix, if desired.
If you wish, dump the water out of the water reservoir and fill with fresh water. (I do this because I don’t like the black water that drips from the potting mix.)
Keep an eye on the water level in the reservoir and add more when it runs low. Try not to let it ever run dry.
Never add water to the top of the planter, add it directly into the reservoir. The soil and plant’s roots will absorb all the water they need right from the reservoir.
To make it easier to move several of these planters, I put them in laundry baskets from The Dollar Store.