# Ask a Question forum Dripline calculation

May 28, 2015 9:16 AM CST
Orange County, CA (Zone 10a)
I've always thought that the dripline was measured from edge to edge (diameter) versus trunk to edge (radius). Is this not correct? Saw instructions the other day that calculated based on radius and thought I'd research it. There was a curious lack of explanation on almost everything I came across. Lots of diagrams showing the dripline to indicate its outer limits, but nothing to show how the actual linear distance of it was calculated.
May 28, 2015 10:09 AM CST
Name: Jean
Prairieville, LA (Zone 9a)
For most of the sites researched, the dripline is determined by the widest branch span. This first link gives the formula for critical root zone calculation, and includes a chart showing dripline info. I hope this helps.

http://www.extension.umn.edu/g...

http://www.ehow.com/how_811608...

http://en.wikipedia.org/wiki/T...
May 28, 2015 11:39 AM CST
Orange County, CA (Zone 10a)
thank you. funny how they won't just come out and say it's the radius. but i think i have it straight now ;)
May 28, 2015 3:42 PM CST
Name: Jean
Prairieville, LA (Zone 9a)
If it gets too easy everyone would do things themselves and the "in the know" folks would be out of a job.. Glad it helped.
May 30, 2015 9:54 PM CST
Name: Elaine
Sarasota, Fl
The one constant in life is change

At the risk of stating the obvious, most trees are decidedly asymmetrical, not perfect circles, and the drip line will be an irregular area at best. Plus the roots will extend sometimes several feet beyond the drip line so if you're calculating the area for a tree to be watered, take that into account! Also, quirky plants that they are, if they have a long branch extending out one way, chances are they have a long, strong root out in the opposite direction to keep from falling over.

Mother Nature's a pretty awesome engineer, but straight lines, right angles and perfect circles aren't on her list of specs.
Elaine

"Success is stumbling from failure to failure with no loss of enthusiasm." â€“Winston Churchill
May 30, 2015 10:54 PM CST
Orange County, CA (Zone 10a)
so true, thanks!
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• Started by: maxcaviar
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