You mean once or twice a *week*, right? And that's only if it doesn't rain....

When depends on the type of irrigation. Drip can run pretty much any time. Overhead watering should be done in the morning.

A lot depends too on if you plants are drought tolerant but Mad is right overhead watering should be done during the morning so the leaves have time to dry and to prevent mildew on the plants.

Except for my veggies, most of my flowering plants are drought tolerant and need very little help from the garden hose.

Penny

Yup, morning is best.

But watering deeply once a week is far preferable to shallow frequent watering. Deep watering encourages deep roots.