I just planted boxwood topiaries on my covered front porch that faces the west. How often should I water these topiaries? They are planted in urns.
Do the urns have drain holes?
Yes they do.
That's good, you don't have to worry about excess water being unable to escape. Just water when dry.
Purple 's answer is the best one. No one can tell you how often to water any plant ; that task depends upon too many factors! Only you can judge when it's time to water by testing the moistness of the soil.
Hopefully, you're using a medium that is porous, allowing the water to travel throughout the pot so that it can do its job and then drain quickly from the bottom.
I will suggest that you water thoroughly on watering day, never with sips. Stick your fingers into the soil to help determine moistness. Or better, purchase a small gauge dowel rod, sharpen it, and insert it to judge how wet the soil is....ot not. The rod will be cool and damp if there's a lot of moisture.
If I were you, I'd check frequently until you become more experienced.