Adding drip irrigation to an urban planter box is one of the easiest ways to keep container plants healthy while saving time and water. Start by checking your water source and the size of your planter box. If you have a nearby outdoor faucet, a simple micro-drip kit with a timer, pressure regulator, filter, 1/4-inch tubing, and small emitters will work well. If you do not have a faucet, use a gravity-fed reservoir such as a bucket or rain barrel with a shut-off valve, or a small low-pressure pump.
For a single urban planter box, 1/4-inch micro tubing is usually enough. For a long box or several containers, run a 1/2-inch mainline and connect 1/4-inch lateral tubes to it. Choose emitters based on plant needs: about 0.5 to 1 gallon per hour for herbs and small flowers, and up to 2 gallons per hour for thirsty vegetables. Pressure-compensating emitters are helpful because they deliver more even water across the planter box.
Before installing the emitters, flush the tubing to clear debris. Then punch holes near the root zone of each plant, insert the emitters, and secure the tubing with stakes or clips so it stays buried under mulch but out of walkways. Add a timer to run the system in the early morning, and start with a short cycle such as 5 to 10 minutes. Test the system, check that every emitter is working, and adjust the run time as plants grow or weather changes. Keep the planter box draining freely, and check the filter and emitters monthly. In cold weather, drain the tubing and store the timer indoors to prevent damage.