There is a lot of interest in container gardening for many reasons. People like pottery. Also many people rent and do not want to plant in the ground or do not have areas that can be planted. But most of all people like to decorate spaces with plants that otherwise would be empty.
In Tucson, planting outside in pottery can be a real trick. With indoor plants, over-watering can be a concern; however, outdoor pots are a different matter. Most are under-watered. This is especially true for plants that are kept in the sun all day. If possible, place the pot where it gets afternoon shade. Six hours of sun is usually enough for most plants. Plants that are shaded by trees or other plants still get light but avoid the heat of the sun in a pot.
Pottery in the sun can be 50 degrees F above the air temperature. Go out and feel the side of the pot in the noon sun. On the hottest day, the temperature in the ground below the top four inches of soil never reaches l00 degrees F. But a pot that is at l50 degrees F or close to it is very rough on the roots of plants. There are obviously no plants in the wild that grow in pots.
If you go into a nursery in Tucson in the summer, you will see people watering all the time. With few exceptions, every plant is watered every day. Pots get hot and they get dry,
The potting soils in use today have been formulated so that they can retain moisture without remaining wet and also have air pockets to retain air, which is needed by most plants. The exceptions are aquatic plants and bog plants. Most plants cannot take this much water.
Watering every day accomplishes two things:
(1) It keeps the plants watered to keep moisture in. Most, about 90% of water that plants take in, is gone through transpiration in about four hours. This transpiration keeps the plants cool. Desert plants generally have small leaves because it is easier to keep small surface areas of leaves cooler with very little water.
(2) The water cools down the soil to make it more livable.
Hand watering is preferred over drip irrigation on pottery, because it covers a larger area of the soil and can cool it down. Drip irrigation goes down in a narrow column very slowly and misses much of the soil. Because it is so slow, it doesn’t do much to help cool the pot down.
Watering the right way can make a big difference in plants thriving or just existing.