Wednesday, August 6

Water works

Designing a drip irrigation system for containers

An otherwise plain patio becomes an abundant garden through the use of containers. And drip irrigation is the easiest and most effective way to provide individualized care for this wide variety of plants. Photo/Proven Winners

Designing with containers is one of the fastest growing segments of modern ornamental gardening. Each new season brings hundreds of stylish yet easy-to-use products and materials — from sumptuous fired-clay, porcelain and lightweight resin pots to specially designed soil mixes. There are even new plants bred for smaller spaces and lower maintenance.

But container gardens still have certain basic needs — first and foremost being a reliable source of consistent water. Containers are generally packed more tightly with plants, and their exposed surfaces and smaller soil volumes dry out very easily, especially during the high heat of midsummer. Add in our busy schedules and you have the real possibility of losing a container garden to “permanent wilt” just when it’s reached its peak. Fortunately, there’s a sure-fire way to get our containers the water they need with a minimum of fuss.

Technology to the rescue

Drip irrigation applies water in a slow, highly directed flow that penetrates to the root zones of plants with little evaporation or run off. It can be as basic as a line from a slow-running faucet to a single pot, or involve multiple watering zones, variable flow water emitters, and computer controlled timers.

The main part of any drip system is the controller. This is an assembly made up of a faucet connector, backflow preventer, line filter and pressure reducer. A Y- or T-connector is often used to let the drip system stay permanently attached to the faucet while a second connection is available for another hose. Backflow preventers are required by law to keep contaminated water from moving back into the system when the pressure is off. Line filters trap large particles that could become caught in the lines or clog the emitters. Pressure reducers regulate city water pressure, usually 60 psi, to keep it from blowing out the tubing and to maintain a consistent flow to every emitter in your system. A reduction connector attaches standard size plumbing to a 1/4-inch “spaghetti” main feed line. This main line runs close to the container area, then connects side lines with small L- or T-connectors to branch off to the individual containers. Each branch line ends in an emitter designed to drip a specific number of gallons of water per hour (gph).

Drip emitters are designed to provide a specific number of gallons of water per hour to each container. Photo/Glen Seibert

Building a drip system

If all this seems a bit intimidating don’t worry. It sounds more complicated than it is. You can get your feet wet with a kit, which comes with all necessary parts, tools and instructions to walk you through the design, assembly and installation of a system. Kits are a great way to get the feel for how emitters operate and how long they will need to run in your specific containers. They are also relatively inexpensive. A complete system that can accommodate as many as 60 containers costs less than $100.

Step 1 - Layout your containers. The best thing about this kind of gardening is that it’s all completely mobile. You can move everything around and try all kinds of different arrangements and combinations. You can even group plants that normally aren’t seen together because containers let you control individual soil and moisture conditions. Keep in mind that hanging baskets are more exposed and dry out more quickly than large containers clustered together, and that full sun plants will need more frequent watering than shade-growing containers.

Step 2 - Estimate each container’s needs. Emitters come in 1/2-, 1- and 2-gph drip rates as well as spray heads for plants such as Boston ferns, which like an occasional misting. A small 8-inch pot may only need a 1/2-gallon emitter, while a huge 30-inch focal point container could require three or four 2-gph emitters.

Step 3 - Assemble the controller parts. The components that make up a controller usually go together in the order listed above, but check your kit’s directions to be sure. Attach this assembly to the faucet.

Step 4 - Run the main line. Attach the main 1/4-inch spaghetti tubing line to the controller with the reduction connector and run the main line close to your containers. You can equip the end of this main line with an emitter and place it in the last container, or plug the open end.

Step 5 - Add branch lines. Measure and cut the branch lines, attach them to the main line with T-connectors and run a line into each container. Leave some excess to accommodate moving the containers as the plants get larger or you change the design layout. If you make a mistake and cut a line too short, just splice more 1/4 inch spaghetti tubing into a T-connector, add a short scrap of tubing to the open end of the T and then close the scrap line with a “goof plug” — a solid cap designed especially for the inevitable goofs that can happen to even the most experienced of us.

Step 6 - Add the emitters. Connect a 1-gph emitter to each line and place it in the container near the center. Clips are available that attach to the sides of containers or are pushed into the soil to hold lines and emitters in place.

Fine tuning and tweaking

Once you’ve installed all the lines, turn on the system and see how it works. Each emitter should be dribbling a slow stream of water that will soak straight down into the plants’ root zones. Run the system for half an hour and then test to see if each emitter is giving its container enough water by inserting a 12-inch-long screwdriver into the soil. If the shank comes out moist, great. If it’s dry, run the system another half hour and check again. If a container is getting too much water, replace the 1-gph emitter with a 1/2-gph size. Continue tinkering with emitter sizes and running times until each container is getting just the right amount of water.

If there is a huge discrepancy between the water needs of different containers, use more 2-gph emitters in the big pots or add a tiny control valve to the lines running to the smaller ones and turn them down to a lower flow. If you have the faucets you can also create different watering zones dedicated to serving containers with similar watering requirements.

For even more convenience, add a timer to the system. Simple mechanical timers (under $20) are turned on manually and turn off when a pre-set amount of water runs through them. More elaborate computerized timers, which range in price from $50 to about $75, can be programmed to run at specific times and days of the week.
Some systems have an optional mixer port at the filter that lets you add fertilizers to the flow. This can be a simple port to pour in liquid fertilizer or a chamber that holds a slow-release fertilizer tablet.

There’s really nothing complicated about installing a drip irrigation system to your container garden. But it does require some thought and planning. Watch the containers carefully for a couple of weeks until you’re sure how the plants are doing, then sit back, relax and let your drip irrigation system take care of the rest.

Active in the horticultural industry since 1994, Glen O. Seibert is a former editor for Garden Gate magazine and now works as a writer, landscape designer and self-professed “gardening media mogul.”