Now if your mind is spinning a bit after reading this, I well understand. I have puttered with plants for no short time and still struggle with finding the “right” fertilizer combination and frequency of application!
Having so noted, it’s wise to remember that very few of us have “the perfectly balanced” natural soil mix for whatever tree, plant, flower, vine or succulent we’ve just acquired and eagerly anticipate adding to our garden collection. Hence, it is rather important to know what our new acquisition might like in the way of additional nutrients. Doing so, we enter the interesting world of plant fertilizers and soil supplements. But, once here, how do we know which is the right one for our specific needs?
One of the most important aspects in this quandary lies in those numbers posted on the bags or boxes of fertilizer? For instance, if you bought Miracle-Gro you might have noted it was valued at 24-8-16. Now while recognizing that this is, obviously, a rather good chemical nutrient balance for flowering plants and vegetables, exactly what is the make-up of this balance?
Well, those numbers are the NPK values. They represent the three “macro-nutrients” plants, generally, most gardeners seek: N – Nitrogen, P – Phosphorus and K – Potassium. I know, I know, potassium doesn’t start with K but just believe me on this, OK?
But what’s so important about these three? Nitrogen (N) is primarily responsible for leaf growth. Phosphorus (P) is a developer of roots and flowers. Potassium (K) is a generalist, helping overall plant functions.
Different species like (read “need”) different combinations. Recommendations from professionals, in that regard, I’ve found are often a bit subjective and vary from one botanical individual to another.
For example regarding palms, while I’ve long used a simple, balanced mix of 16-16-16 there are no few who would hotly disagree. (But before caving to their dictates I might invite them to come see our success here at Ola Brisa Gardens!) However, there are numerous palm professionals I know of who use anything from a 3-1-3 or 12-4-12 with 15-5-15 being the ideal (note those ratios are consistent), to an 8-2-12, 11-4-11 or 13-3-13 mix.
But before continuing, let’s gather a bit more data about those confounding numbers.
If the fertilizer contains only one of these macro-nutrients the other values will be “0”. For instance, if it is labeled 0-10-0, then it only contains phosphorus. And, I suppose rather obviously, the higher the number is the higher the concentration of that nutrient will be. Hence 20-20-20 is twice the concentration of as 10-10-10.
“But how much of it should I use?”
When incorporating a palm tree fertilizer, one does, indeed, need to successfully calculate how much the correct amount should be. A simple rule of thumb is 1.5 pounds (.6 kilos) per 100 feet of canopy. Don’t get hyper at this point as it’s reasonably easy to figure the canopy size of your palm.
To do so, simply walk out from the trunk to the farthest tip of the fronds and then draw an imaginary square around the trunk following the outside edges of the leaves. (This measurement is called the drip line.) If your square measures ten feet by ten feet then the canopy would be 100 square feet. Accordingly, that would mean 1.5 pounds of fertilizer for that tree, per feeding. Now that wasn’t that hard, was it?
Here let us note that a slow release or delayed release fertilizer is better and safer than rapid release. But, while perhaps preferable, they cost more – there always seem to be trade-offs in life, right?
Beyond that, if possible, one should endeavor to get a fertilizer that includes “micro-elements” such as magnesium and iron.
But at the top of this entire subject are two cardinal rules: Never use too much fertilizer or apply it on dry soil. (And we might simply encourage you to follow the directions!)
There are some further “Ya’ need to remembers” such as:
- Work the fertilizer into the soil if at all possible.
- Water your palms thoroughly after fertilizing.
- Be aware that it is better to under-fertilize rather than over-fertilize.
- Fertilize completely over the entire root distribution area.
- If possible get a fertilizer with magnesium and calcium supplements and ample micro-elements and/or, if available, consider organic fertilizers such as dried cow manure (what I use copious amounts of), blood or bone meal, fish emulsion and worm castings.
- Add fertilizer to organic top-dressings – I used fibre de coco (coir) which is coconut fiber (the torn apart husks of coconuts).
- Make your own determination as to whether or not to fertilize year around. Here in Manzanillo I do. . . . adjusting for each plant.
- Once you find a fertilizer that works and your plants are growing well, stick with it. Remember the old axiom “Go home with who brung ya’!”
- And lastly, don’t be afraid to ask your friends and neighbors what has worked for them!
As to some “Don’t Do’s”:
- At the sake of repeating myself, never fertilize on dry soil or fail to water after fertilizing.
- Don’t throw granular fertilizer down the palm’s crown of the plant, in a pile at the base of the plant, against the trunk of the plant in a mound or directly in contact with the roots – as when re-potting/planting.
- Don’t fertilize immediately when planting – wait about four to six weeks later. But do consider using a root stimulant when planting.
- Never assume that foliar spray fertilizers are adequate for all the plant’s needs.
- Don’t allow rain to fall on your stored bags of fertilizer.
- And store your fertilizer on a pallet and cover ‘em with a tarp or do as I do by securing them in large plastic barrels with lids.
“How about specific plants?” In a wholly “ballpark” range, cycads seem to care more for something around 24-7-8; bromeliads appreciate 18-9-27; caladiums seem to thrive well with a 5-1-10 mix while ferns generally like something around a 20-1-20 but tree ferns prefer 26-6-11.
Well, that’s a lot to remember isn’t it? But don’t worry. Those plants were fairing quite well long before we came onto the scene with our array of great fertilizing ideas!