Hortaholic said: Hi @PicoAzores,
You are wise to be concerned about the possibility of applying excessive phosphorus, not just to your trees but also to the soil, where it might runoff and cause pollution.
The 12-12-17 ratio of that fertilizer means it has more phosphorus than the palm tree can probably use compared to the amounts of nitrogen and potassium. It would be better if the middle, phosphorus number, was more like 4.
You can offset this by using less of the fertilizer than would be optimal to get maximum growth (which usually means applying more nitrogen). The fertilizer package may have directions for the amount to use per square meter (or another area size). Calculate the amount this would be, proportionally, for the rooting area around your palm tree. Then reduce it to only 1/3 of that amount to keep the phosphorus low enough. Palms have dense fibrous root systems close to the trunk. Look for information online about fertilizing them.
It appears that your islands have a range of soil types (link below). Some of them will hold phosphorus against runoff. Others won't. Although holding the P from runoff is good for the environment, it can be bad for your tree as the phosphorus can eventually build up to levels that are too high.
See if you can find out what type of soil is in your garden.
https://revistas.rcaap.pt/rca/...
Best wishes! Sometimes I wish I lived where palm trees grow.🌴 Most of the time I'm glad I at least get to visit them once in awhile.
Pat
Hi Pat,
I understand I should use less of the fertilizer as if I was just phosphorizing the plant and not much adding N-K for it. So instead of a good handful I will add just a tiny bit around the tree. Yet supply of fertilizers variety and instructions of use is very poor in Portugal and in the Azores islands. You can visit Azores if you have heard about them. It's an easy 4 hour flight from Boston or NYC to the Azores. 9 islands tota and all are different. The climate is like the tropics minus 20F or 10C which means when tropical climate is 20C to 35C (68F to 95F) the Azores is 10C to 25C roughly or 50F to 77F which means it is the same climatic pattern but reduced by 10C. Thus palm trees grow, but only those which can survive without much heat above 27C or 80F. So those palms that need constant 90F or more year round can't be grown in the Azores. I have already made research what tropical palms grow best in the Azores and am growing only those palms. Areca catechu is one of those palms and but it grows so slowly that instead of 15 ft. it is only 5 ft. in height after 10 years of life. Others such as Washingtonia or even Bismarckia are growing quite fast I would say, despite lack of year round heat and even lack of summer heat above 80F. If you can consider an occasional 78F-80F for a couple hours per day a "heat". Otherwise what you get here is 55F to 64F year round with 64F as TOP temperature and 60F as median.
Now regarding our "soil". It's not really a "soil" but rather a large vase... What I mean is that this area was run over by a volcano, lava flows. Thus the "yard" is all solid rock. What I did while I had some funds I bought like 50 trucks of "soil" (dug up from depth elsewhere on the island) and deposited around the field by thickness of about a foot or two feet. Under it is lava stone or solid boulder. Thus not all trees can put their roots deeper than 2-3 feet... and it heats up fast under a sun. Wind topples such trees easily. Can't water too much as supply water is expensive and well or spring is not available here. This is the worst growing conditions ever. Basically means it is equal to growing in vases, cement or stone planters or pots. Trees that like to ave their roots deeper than 2 ft. or let's say 3 ft. are out of luck. Only those trees survive long term that can let their roots into the lava rock or lava slab. Lava slab is probably dozens of meters deep if any soil under it at all. It's a challenge.
I understand I need the formula 3-1-3 or 12-4-12 for my palms. Not in this country. They won't supply me with it even if I paid a million bucks. Thus I must use the only available 12-12-17 or not use it at all.
