I learned about electricity when I was 5.
We were visiting friends on a farm. My dad warned that the fence would zap me while he grabbed one of the uncharged wires to open the gate. Later that day, I studied the gate on my own, but when I wrapped my fingers around the uncharged wire, it grabbed back.
I remember letting out a jittery cry and seeing people running for me in some sort of weird X-ray vision. I had a healthy respect for electricity after that.
Electricity runs our water pumps and irrigation controllers in the landscape, but when it strikes in the form of lightning, it's a problem.
Lightning can hit with 100,000 volts or more. Some sources claim the United States receives 20 million lightning strikes a year and that more than 1,000 people are hit.
Most of us learned to avoid seeking shelter from a storm beneath a tree because lightning seeks the path of least resistance. Trees are tall and the sap and water within the trunk
make a better conductor for electricity than air.
The electrical current of a lightning strike will pass through the trunk and down to the roots before dissipating in the ground. Lightning can generate temperatures of 50,000 degrees that will boil sap and explode cells.
Typically, a strip of wood will be blown off one side of the tree, stripping a streak of bark clear up the trunk. However, trees are likely to survive most lightning strikes, especially when damage appears only on one side of the tree. The wound typically seals, leaving a long woody scar.
When bark is splintered on both sides of the trunk, the odds of survival are much less. Sometimes roots can be severely damaged and death can occur within a few days.
Other concerns may be structural, cracking large limbs that increase the risk of falling, in which case an arborist is best suited to properly and safely remove the threat. A lot of human injuries in the landscape start with a chainsaw, so don't try to remove them yourself.
Lightning doesn't just affect our trees. It also can wreck an irrigation system. A valve uses a copper wire coil, called a solenoid, to open and close the valve. Insulated copper wire connects the solenoid to the controller that sends a 24-volt signal through the wires to turn the valve on.
When lightning strikes a tree and dissipates through the soil, it can leap through the solenoid in a nearby irrigation system and travel back to the controller, flash-frying both.
A few weeks ago, lightning struck a pine tree outside the horticulture building at Trident Technical College. It did little damage except to split one side of the trunk. The tree appears to have survived, but the real harm went unnoticed until the next day.
One of our irrigation controllers was open and had been soaked by the rain. Even the panel was open, exposing the circuitry.
It turns out that three controllers were rendered useless by the lightning strike, their charred circuits melted. A single valve was located near the base of the pine tree where the lightning hit. Since all the valves in our irrigation system share a common wire, the lightning ran throughout the entire system, hitting all the controllers.
Unlike the system damaged at Trident, most commercial irrigation systems are grounded to a copper earth plate. While nothing will survive a direct strike, the grounding plate can dissipate an indirect strike. While residential irrigation systems can be grounded, it is not a common practice since these components are less costly to replace than commercial ones.
Tony Bertauski is a horticulture instructor at Trident Technical College. To give feedback, email him at email@example.com.