Hi there,

Generally, if you are transferring the plants your purchased into a container, you should water it once thoroughly and let the water drips from the drainage holes. This ensures that the soil is watered uniformly. Water again when the top part of the soil gets dried up again.

I do think that most nursery tags assume you're planting in the ground, which means you'll probably water and fertilize a little more often if they're in containers. For full/part sun plants, as long as your pots are draining properly, I doubt root rot will be a problem. Basically, for most annuals and perennials, just water when the top inch or two of soil is dry, which for full sun plants in the deep south summer will be pretty much every day.

Even if you're planning to keep your plants in containers, it's often a good idea to move them to a larger pot than the one they come in from the nursery. If the plant's root-bound when you get it, pot it on immediately. If not, you can grow it in its original container for a while, or move it to a larger one for a group planting or to avoid having to water quite as frequently; many people prefer to move perennials up gradually in container size, so that the roots continue to fill out the space available. A plant in a container that's too small or too large is more likely to have problems with watering.