As Californians scramble to find a way to reduce water consumption to meet a 25% water reduction mandate, turf removal has become the latest means to accomplish significant water savings. From Santa Barbara to San Diego, with Los Angeles and Orange county in between, turf is being ripped out at a frenzied pace.
Considering the rebates offered by the Metropolitan Water District in Los Angeles and other municipalities, homeowners and businesses are jumping at the opportunity to be reimbursed for turf and spray irrigation removal. Succulent gardens, Mediterranean, and California natives and other drought tolerant plant materials are being used to replace water guzzling turf.
The decades long love affair with our green turf lawns is coming to an end. Unless you can afford to pay extremely onerous penalties for excessive water use, the California drought, climate change and dwindling water resources will change the way we design, plant, irrigate and use our landscaped areas.
As turf and spray irrigation is removed, it is easy to forget about trees in the landscape. Trees planted in the landscape rarely receive irrigation dedicated to just the tree. Typically, the tree is located in an irrigated turf or planter area. Tree roots grow where there is moisture. Trees adjacent to an irrigated turf area will certainly root into the turf zone because that is where the water and nutrients are.
A common misconception is trees develop deep tap roots that grow deeply into the soil to locate water. In fact, almost all tree roots grow within the top three feet of the soil mass, almost 80% of the roots grow within 12-24 inches from the soil surface! Initially, a tap root growing downward will encounter rocks, hard pan or other physical impediments causing the tap root to split into a fibrous system growing horizontally through the soil profile.
As roots grow outward from the trunk, the tree crown grows in conjunction with the spreading root system. The outward edge of the tree crown is referred to as the drip line of the tree. The structural tree roots grow outward toward the drip line, however they don’t stop there! Outside of the drip line, the structural roots become increasingly smaller in diameter and that is where the fine absorbing root hairs are located, often well outside of the tree drip line. Many tree species grow roots up to twice the tree crown diameter!
Knowing how tree roots grow is vital to understanding how your trees will react to changes in irrigation caused by converting turf or high water use areas. If the edge of a tree crown or drip line is near an irrigated turf area, it most certainly will have rooted into the turf soil zone. When the turf is gone and water is turned off, the tree will have lost it’s primary source of water and nutrients and will begin to decline. If it does not have or develop other water resources to tap into, the tree will eventually die.
If you notice the crown of your trees declining, not leafing out or new buds dying back, these are symptoms that may be caused by the affects of drought or lack of water. Think back and consider what changes have occurred in the past one to two years? Has there been construction or renovation work nearby? What about changes in the landscape, was the turf removed and sprinklers turned off? Was there trenching, rototilling or soil preparation in an area nearby existing trees?
You can still remove your water consuming turf and use drip irrigation, just remember to plan for irrigating the trees. If using a drip system, consider using higher volume emitters, or other distribution systems that will provide an adequate water supply to the tree. Add a drip valve solely dedicated to tree irrigation separate from the other shrubs or ground covers. Proper planning, installation and maintenance is required to convert water consuming landscapes into sustainable, water efficient landscapes while preserving existing tree health and aesthetics.
With proper planning, trees can be grown and will flourish using drip or low volume irrigation systems but you must provide enough water distribution to encourage the tree to root into the surrounding site soil. Unlike spray irrigation, drip systems must be maintained and upgraded as trees grow larger root systems. Additional drippers or emitters are required as the tree crown increases in diameter. Drip and low volume distribution systems work great but are more labor intensive than spray systems and require a higher degree of maintenance.
So go ahead and get rid of that old ugly bermuda grass lawn, or grit your teeth and say goodbye to your green lush tall fescue or Kentucky bluegrass and say hello to water savings without sacrificing visual aesthetics. You can keep your trees alive and flourishing while still achieve water savings and a unique, beautiful landscape. Use a landscape and certified arborist tree professional to help you achieve your sustainable, affordable landscape!