Sabal palmetto root length?

[Jono Miller]

Regarding the length of roots on cabbage palms, Wade and Langdon cite Sargent (1933) as follows: 

". . .with a short pointed knob-like under ground stem surrounded by a dense mass of contorted roots often 4° or 5° in diameter and 5° or 6° deep, from which tough light orange-colored roots often nearly 1/2' in diameter penetrate the soil for a distance of 15° or 20°, "

 

On the other hand,  at a palm workshop I was told cabbage palms can have roots 40 or 50 feet long.

 

My own observations on eroding beaches and banks suggests 15' or 20' is definitely too short.  See image from Cedar Key.

 

Does anyone have a personal observation or citation for Sabal palmetto root length other than Sargent? 

 

[Jono Miller]

Dent Smith spans the gap in Principes Vol.7  "Growth Rates of Certain Palms"