How to Prepare Terracotta Pots for Planting. Terracotta is clay that has been refined, molded into a shape and fired. It has been used for thousands of years all over the world for pipes, roof tiles, tableware, sculptures, and of course, pots. Unglazed terracotta pots are popular because they come in all sorts of sizes, shapes and styles and are very affordable. The one problem with unglazed terracotta is that it is a very porous material. When you fill an unglazed terracotta pot up with moist soil, the terracotta actually acts like a sponge and wicks water out of the soil-causing the plants growing in the pot to dry out much more quickly than ones grown in glazed ceramic, plastic or wooden pots. Here's a quick trick for preventing terracotta from drying out.
The best way to reduce terracotta's tendency to wick water away from your plants is to pre-soak the pot prior to planting. To do this you must completely submerge the pot in water. Place small pots in a deep sink and fill it with water. Keep the pot submerged for about 30 minutes or until bubbles stop rising up from the pot.
I've found that the easiest way to soak large pots is in a 55-gallon garbage can. Simply rinse any grime out of the can with your hose. Then, place your terracotta container inside the can and fill the can up with water, being sure to completely submerge the pot. Again, allow the pot to soak for 30 minutes or until bubbles stop rising up from the pot.
Once you've soaked the pot, fill it up with potting soil (leaving about an inch between the top of the soil and the rim of the pot). Then water the soil in with water. I know it seems strange to water the soil before you plant, but pre-moistening the soil eliminates the problem of potting soil floating up out of the pot when you water your plants. After pre-moistening the soil, you're ready to plant your pot!
After planting, keep the soil inside the pot evenly moist and spray the outside of the pot with water whenever you water your plants.