NDSU Extension - Griggs County


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August 10

The Extension Connection

By Megan Vig

                Shark week has recently passed.  It is a week devoted to educating the public about sharks and also sharing horror stories of people being attacked by sharks.  Why am I referencing shark week?  Read on to find out why shark week was addressed in the NDSU Extension Yard and Garden Report.

                Rodney Fox was attacked by a great white shark in Australia.  He recalled, “I’m looking through the pink of the water, through my own blood, and I see the head, getting bigger.”  The shark bit into Rodney, ripping open his body, crushing his ribs and puncturing his lungs.  Rodney required 462 stitches to seal his wounds.  Ouch!

                Bethany Hamilton was surfing one day in Hawaii.  Before she knew it, her arm was ripped off by a tiger shark.  She said, “It was about a two-to three-second period and when it… was attacking me all I saw was like a gray blur.”

                Are you scared yet?  Imagine yourself swimming in a pool.  A trap door in the pool opens and a shark is released.  The shark comes toward you.  You can hear the water ripple as it swims, it’s rushing toward you and you are helpless.  This is the way a tree feels when a lawn mower is coming near.  Absolutely helpless!

                Every time you start your mower, every tree in your yard shudders in fear.  Your mower—a machine designed to bite through plants with a sharpened steel blade—will soon be brushing again the tree’s skin.  The mower is one of the leading killers of trees in North Dakota.

                Mowers attack bark, the armor of a tree. Just beneath the bark is the phloem, a precious layer where nutrients are carried from the leaves to the roots.  If you expose the bark, the phloem is destroyed.  If you destroy the phloem, the roots will stop receiving nutrients from the leaves.  The roots will starve and die.  If that isn’t bad enough, the wounds created by mowers also are easily invaded by diseases.

                How much damage to the bark can a tree withstand?  Trees generally survive if the damage is limited to 25% or less of the bark around the tree.  As damage levels increase higher, the tree suffers higher levels of decay and dieback.  If the bark is stripped around the entire tree, it will die.  This is called girdling.  If you love your trees, protect them against your terrorizing lawn mower (and trimmer).  Place a ring of mulch around each tree.  Follow the “3-3-3 rule.”  Place a ring of mulch that is at least 3 feet in diameter around the tree—even more is better.  The mulch should be 3 inches deep.  Keep mulch to a minimum for the first 3 inches away from the trunk.  Heaping mulch again the trunk can create stem rot and provide nesting habitat for bark-biting voles.

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