Question
What is the best fertilizer for Sago Palms and also Mexican fan palms?   

I had two clumps of Paroula(sp.?)palms installed at the seashore near Galveston this past November.   There is a lot of salt spray.  I was assured they could tolerate it since they grow in the Everglades!Hmm.  They look decidedly unhappy.  Prognosis?

What can I use to keep black fungus from getting on my garden grwon Nun's Orchid?

Answer
Use specially formulated palm fertilizers for all the plants mentioned (except the Orchid). Palm fertilizers contain primarly slow release nitrogen as opposed to the common quick release nitrogen sources found in stores (e.g. ammoniacal or urea nitrogen). Slow release fertilizer is recommended. Palms generally require higher levels of magnesium, potassium and manganese.

Unfortunately many PALM fertilizers today have been "re-formulated" to be similar to most other plant fertilizers e.g. they have gone from high quality to junk quality. You need to be able to read and understand a fertilizer lable to buy a good quality palm fertilizer today.

Look for ratios such as 8-4-12. e.g. a ratio (RATIO) of 2-1-4. A different product with a similar ratio could be 10-5-15. Also look for micro nutrients such as iron, boron, zinc, manganese, magnesium. Especially magnesium and manganese are CRITICAL. Get a fertilizer which has at least (AT LEAST) 3% of the last two on the lable.

You may not find these fertilizers as PALM fertilizers. you may find a rose fertilizer or orchid fertilizer matches these requirements. if so, buy it. Especially the SAGO needs the micro nutrients (magnesium, manganese) to survive and be happy.

Another way is to buy a fertilizer like 14-6-6 and then add a little bit of sulfate of potassium (0-0-50) to make up the potassium difference (e.g. to get it to 14-6-"28").

Give your palms a dose of EPSOM salt. EPSOM salt is magnesium sulfate, e.g. it contain magnesium (10%).

Fertilize the palms about 4-6 times during the year.

You may have to do some looking around. The key ingrediences to find are:
- magnesium, manganese, boron, potassium
- look for ratios such as 2-1-4 (4-2-8, etc).
- consider single nutrients to make up any shortfalls
(sulfate of potassium, epsom salt, etc)
- look for containers with nitrogen in slow release form. e.g. fertilizers which has the product coated for slow release. Examples are nutricote for example.

I am not familiar with salt tolorance of ferns. I don't grow orchids either, sorry.