Palm Pro label:
Use 1 to 2 oz ounce per gallon of water as a soil drench and foliar fertilizer. You can foliar fertilize every week for two or three months for a faster green-up, with the solution in an ironing-type spray bottle. Spray top and bottom of leaves.
I have used this one for my customer's palms and cycads, spring and fall applications, with good results. It has a lot of goodies in the formulation:
Here's another possibility, but I have no personal experience with it:
This article also discusses important water management factors: