As we strive to cope with the current drought – which has now lasted about 4 years – we must be sure that our state’s street trees do not get lost in the shuffle. Not only do street trees improve property values, reduce crime and improve the health of those living near them, they help mitigate some of the effects of the drought.
For example, street trees actually help keep our cities cooler by about 5 to 9 degrees Fahrenheit, which reduces the evaporation rate and allows more water to stay in the soil. They also provide shade, which – when placed over external air conditioning units – improves the efficiency of our climate control systems and reduces our carbon footprint. Street trees also help to break up the heat island effect, which further cools our cities and towns.
So, given that our trees are important, but water-intensive, resources, how do we go about protecting them efficiently?
The Right Way to Water
One way is by providing water slowly, which ensures that the water we do allocate to trees is effectively absorbed by their roots, instead of simply running off the soil and down the watershed. Additionally, we must ensure that we deliver the water effectively and do not waste water by spraying it on the tree’s trunks, canopy and the adjacent sidewalk, as sprinklers often do. In fact, up to half of the water a sprinkler broadcasts over an area evaporates before a tree’s roots can absorb it.
Slowly watering trees is not only beneficial from a water conservation viewpoint, it is better for the trees themselves. Lightly watering a tree on a frequent schedule – such as we do when watering our lawns — encourages the development of shallow roots. While this is not a problem for grasses, it is less than ideal for trees. Shallow roots prevent the tree from tapping in to deep water sources, which would help them survive future droughts; but shallow roots also predispose trees to wind throw.
Unfortunately, it is not easy or cheap to water a large number of trees slowly and efficiently.
Or is it?
Enter the Irricade
In 2014, Tree People – an LA-based nonprofit group, dedicated to growing a “green and climate-resilient Los Angeles” — began experimenting with an Australian solution for watering urban trees. They call them irrigation pods or irricades, and they have proven to be surprisingly effective.
Essentially, irricades are hollow traffic barriers (sometimes called Jersey barriers or K rails), filled with water and fitted with a soaker hose. The irricades are placed in suitable areas near the trees (but far enough away that their weight does not harm the tree’s roots) and the soaker hoses are placed in the appropriate places around the root zone.
As the water (about 160 gallons, depending on the exact model used) slowly drains from the barrier and through the soaker hose, it gets absorbed by the soil, and, ultimately, the tree’s roots. Because they distribute the water via a soaker hose, rather than a sprinkler head, the waste is minimal. Further, because the water slowly trickles into the soil, irricades do not waste water via runoff.
There are four primary reasons irricades are so effective:
They rely on existing, “off the shelf” components that are not cost prohibitive.
They hold a useful quantity of water. Most small street trees require only one irricade, while the largest trees require no more than three.
They require minimal labor to utilize. Aside from setting the irricades in place, they need only be filled and inspected weekly.
You can use recycled or gray water to fill the irricades, which saves even more water.
Tree people and the Los Angeles Department of Parks and Recreation placed an initial batch of irricades in several places in 2014, and other locations have followed in their footsteps, so you may have seen irricades without realizing what you were looking at.
Some have complained that they are an eyesore, but most residents have responded favorably. One things for certain, given their renewed vigor, the trees benefiting from the devices are grateful.