Actually.... if you google it, you will find that epsom salts is very much recommended for palm trees.
How to Apply Epsom Salt to Palm Trees | eHow
Epsom Salts for Palm Trees? | Ask Mr. Greenthumb
"Berni P. wrote:
Looking for info on palm trees. Is there any value to adding epsom salts and if
so, how much?
Dear Berni:
My book titled, Stan DeFreitas Complete Guide To Florida Gardening, has a listing of
palms and information. Magnesium sulphate (epsom salt) is one of the macro-elements
and is used in a higher amount than the micro-elements. It will help to green up your
palms. Normally a couple of cups spread evenly around the palm will be helpful. Use
no more than 3 lbs. on a big palm.
Hope this is helpful.
My Best,
Stan"