Wednesday, December 28, 2011

A Rant On Liquidambars

 Our recent breezy weather is bringing out lots of concern about the safety of trees planted next to houses. I recently had an inquiry regarding one tree that should never be planted near houses or any hard-scaping for that matter...and it's not a Ficus.

Liquidambar styraciflua is a tree native to parts of the Southeast United States, Mexico and parts of Central America. It’s called a ‘Sweet Gum’ because Native Americans would chew the tree’s resin like chewing gum.  The tree is not at home here in dry Southern California. Where it's native the precipitation averages 25-35 inches of rain a year. The problem is that it is also a tree that has evolved to survive in rocky, infertile soil in its native range.  This ability to ‘tough out’ those harsh conditions makes it appear to be the perfect tree for Southern California; nothing is further from the truth. With the dry winds and the infrequent precipitation Liquidambars here are constantly under water stress.  They also have the propensity to develop very invasive and destructive roots.  But wait there’s more. Ever since 1998 when a new pest called the ‘glassy winged sharpshooter’ was introduced to California Liquidambars have been infected with a disease called ‘scorch’.  First appearing on Oleanders, this disease is a bacteria that plugs up the water conducting tissues of the plants it infects and causes the shoots furthest from roots to dry out so fast they literally ‘scorch’ where they stand.  This has gotten so bad in parts of Riverside county that it causes the trees to die back to almost 2/3 of their former height, causing them to look disfigured and leading to their removal for aesthetic reasons.

Now also consider that the  chances of damage from the wind toppling Liquidambar  trees is  probably not as great as the chances that the trees roots will damage some structure that the tree is within 10-25 feet of. 

So all this leads me to my final opinion on yours, and every other Liquidambar tree growing in Southern California. Unless your tree is at least 25 feet away from any structure it can damage with its invasive roots, and is surrounded by a lawn (which is the only way it’s going to get sufficient water to remain healthy and tolerate the effects of the scorch disease) I would remove the trees and plant something else.

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