This is the best palm food. Maybe you can find something similar.

https://www.bgi-usa.com/palmgain/ 

I know nothing about this but it appears this retailer is on the azores.

Maybe they can help you.

https://agriloja.pt/

with water soluble fert.. you can manipulate the fertilizer simply by mixing it at half strength ..

frankly.. in my experience... i never used any fert full strength.. as i figured out the sellers were ripping me off for profit.. and half was just as good as full strength ... you can always redose in a month or 3 if you think it needs more.. but as you note.. if you burn a plant.. there is nothing else to do... until it outgrows the damage...

now.. why do you think random trees in your yard/garden.. need fert???

if you are growing them in pots.. you may have forgot to mention such...

have you ever had a soil test performed.. to understand what is lacking from you soil or potting medium .???? ... you base problem. is you dont know what you need.. so you cant interpret how this product fits in that spectrum....

ken

I rarely fertilize anything, but I bought this bag some years ago, just to try and used most of the bag on fruit trees, with unknown results. Now why would I use fertilizer on palms? Because our climate is lacking heat most of the year (55F to 80F) with most temps around 60F to 75F while about 9 months per year it's 55F to 64F. Therefore some palms grow very slowly.

Let's take Areca catechu, which is like 9-10 years old by now but only about 5 ft. tall. and it should be more like 15 ft. tall if it was growing in a hot climate.

I even am surprised Areca catechu grows here since Satakentia liukiuensis, no matter how hard I tried to raise the 10 seedlings of it all died.

I guess I should sprinkle less of the fertilizer around the palms. I must add that over a decade ago, in the US, I have killed all of my potted palms by sprinkling instant release fertilizer into the pots around the palms and now I never add fertilizer into the pots. Even if I wanted, I could add a slow release fertilizer, and I still have half a bag of slow release fertilizer that I purchased in the US some 15 years ago, and I do still use it sometimes, in small amounts. Not sure if it works anymore though. Locally it is not possible to even order anything specific for palms, and even many goods can't be shipped to the Azores. Some businesses just don't want to ship anything to the islands.

What I struggled to find especially is Epsom Salt. No matter how hard I tried to find it or even order it from an Agricultural Coop, I was unable to convince them to order it for me, as they usually say it's not available in the entire country. And these days everything has become unaffordable due to living cost and grocery we just spend all the income on food. So whatever palm seeds I have germinated till now, whatever I purchased in the past we must use for the rest of our days. This is why I use the fertilizer sparely, whatever is left of this 5 kg bag and another 5 kg box is still half full.

Regarding NEED, I believe trees could benefit from cow manure rather than fertilizers. So whenever we see a big pile we will pick it up and bring it home. But we have not used cow manure much enough as we should do that on a much larger scale. It just the fuel for the truck is usually too expensive (at around $8 per gallon and or 23 MPG fuel efficiency) to drive around collecting cow manure here and there.

Regarding soil tests, those I try to avoid as I know nothing about the topic as it seems complicated enough. Even if we did a soil test, and learned to understand the result, there would be not enough ingredients or funds available to upgrade the soil. Thus we use what we already got. We compost everything, and use food scraps ash and cardboard for compost, then add it to the soil. Currently I am trying to save enough money to bring 5 trucks of soil into my place for a variety of uses. Good soil is hard to come by but one guy has got lots of it, just have to pay and make sure it becomes screened, reducing number of large boulders in it. €200 per large truck.

As a final thought, all what we grow is for our own use, including the palms, just for beauty, but I was able to do an occasional sale several palms for a scarce hobbyist on the island.