Irrigation, along with fertilizing, of container gardens is critical because the containers are closed systems.
The needs of moderate or larger installations are best met with simple drip irrigation and fertilization systems which require no electricity. Hiding the feeder lines for aesthetic reasons is one of the key features of the containers I design for DeepStream Designs.
While most plants do best with a consistent soil moisture content, many need to dry out between water applications. Of course, some plants require special over or under irrigation. A multi-valve multi-line drip irrigation system can use automatic timers to achieve both effortlessly.
The picture above is my manifold setup, which along with the drip irrigation on 4 circuits, was installed in a single afternoon.
To simplify your irrigation, it is best not to mix plants that may need different types of watering, fertilizing or soil in the same container.
While this concept can also be extended to root depth, in larger planters it can actually work quite well as trees or bushes with deep roots can benefit from the needs of flowers with shallow roots that dry out more quickly to be watered several times a day with a topical water spray which can augment a deeper root drip irrigation line fed by a line on a different timer.
Generally, I run at least two 1/2″ main irrigation lines to feed perimeter planters: one for the deep-rooted plants watered by drip irrigation soaker hoses with emitters on 6″ spacings, and another with sprayer and/or misters that either hang from taller trees or bushes or stand on spikes.
In every case, I use in-line micro-valves on every 1/4″ feeder line from the 1/2″ main irrigation line to tailor the water delivery of each line to the planter, as the micro climates of each planter may vary considerably depending on exposure to sun and wind.
Delivering micro-doses of fertilizers on a consistent basis precludes the trough and peak delivery of single monthly doses of liquid fertilizers or the irregular dosing provided by slow-release coated dry fertilizers that depend on rainfall to dissolve. Plants do better with this type of consistent feeding.
An advantage of installing different main irrigation circuits for different types of plants is that a fertilizer injector system can be installed upstream of the valves. Running one valve at a time, you can meet the needs of different plant types with different types and proportions of fertilizers with just the flip of a switch.
A visit to Dripworks’ catalog will give you a good overview of the types of irrigation products available that make this very easy, even systems that work on elevated rain barrels.
Reservoir planters and planter liners are another form of irrigation that will work when you have plantings with similar root structure and no running water. These system use a bottom up water supply so if you have different plants, some with shallow roots that need more water and others with deep roots that need less they do not work as well as the top down found in nature.