I put some 1/2 in. -1 GPH Pressure Compensating Drip Line irrigation hoses like the ones in the link below around my new plant beds under mulch.

My longest run is about 75 ft. Shortest is about 10 ft.
The water is coming from in-ground hose bibs tied to the sprinkler meter outside & using an orbit manual timer.

How long should I be keeping the timer on for?

Unfortunately, we had to plant in the heat of summer & because of a lack of consistent rain, a couple of daisies died after being in there for about a month. But the rest are putting up a good fight with the beds getting drenched by some manual oscillating sprays of about 15-30 minutes once a week.

The fighters are a mix of catnip, hydrangea, viburnum, barberry, shamrock holly, blue prairie grass.

Here is a link that might be useful: DIG 1/2