Controlled Release Fertilizers-Fertilizing the Economical Way

One of my biggest contentions in horticulture in this area of the US is that people underfertilize their plants. It has gotten to the point that I see malnutrition in almost every municipal landscape I see, especially in xeriscape landscapes. It seems almost a dogma that plants are installed without additional fertilizer at planting time, then allowed to dwindle away to the point of no return. This is easily manifested and seen in South Florida in the larger palm species, with a trademark yellowing of lower fronds. For 20 years I have heard landscapers say that such lower-frond yellowing is normal. It is absolutely NOT normal for the lower fronds on a palm to be yellow; this is a clear sign of malnutrition and under-fertilizing. I see Oak trees stay the same size for decades, as well with many highway and residential plantings. It is apparent that many landscape installers feel that fertilizer is an unnecessary expense, especially in municipal plantings. I can't help but wonder why this is. It would be difficult to quickly change municipal planting codes in many cities, but perhaps I can appeal to residential gardeners.    

retail packaging of commercial-grade Nutricote fertilizer

commercial version of Dynamite fertilizer

the venerable Osmocote

a famous and recognizable brand in many formulations

fertilizer spikes for in-ground use around trees and palms

I have also heard that people don't want to fertilize their plants for fear that the plants will grow too fast and become a maintenance hassle. I have a great urge to yell "REALLY ??!!" What a bizarre concept ! Fertilize the plants properly, and they will grow properly ! Plants, pets, people, and most any living organism need some sort of nutrition source on which to grow and thrive. To starve plants to avoid having to clean up after them is a curious tactic, akin to starving your pets to avoid cleaning up after them. Plants are supposed to grow, yet we complain they grow at all.

I also realize that many people may not know the technical ins and outs of fertilizing plants, but there are ways to help your plants and minimize your care of them. One of the best long-term fertilizer management strategies is to use controlled release fertilizers, usually called "slow-release" fertilizers. Two applications per year of these CRF products will do the job in the warm subtropics, and one application in the northern climates will provide enough fertilizer throughout the growing year. There are many brands and types of CRFs, and they all work to some degree or other. It would be safe to say that a CRF is more economical to use than a water-soluble or quick-release fertilizer, with caveats. One of the caveats is that the longer-term CRFs start their release slower than the over-the-counter lawn and ornamental fertilizers do. This slower initial release often misleads people into thinking the products don't work ( people often want instant  gratification). You can also control plant growth more accurately with water-soluble fertilizers than CRFs, but they are shorter-lived in the plant than the longer-term CRFs.

Many organic fertilizers act as CRFs, and they all work to some degree or another as well. It is helpful to find out what your plants need to make sure you choose the right fertilizers. Here are some helpful ideas:

1.  for plants that are used for their foliage, or those that need foliage to make flowers ( herbs, Canna lilies, Heliconias, many gingers, etc), than use a slightly higher nitrogen fertilizer such as 15-6-12, or a 3:1:2 ratio of N:P:K.

2.  For those plants where leaves and stem or root development is needed, ( cane begonias, butterfly gingers, bulbs, etc) use a more balanced fertilizer ratio such as 15-5-15, or a 3:1:3 ration of N:P:K.

3. Many flowering plants like a very even fertilizer balance, such as 13-13-13, or a 1:1:1 balance of N:P:K. Some orchids and flowering plants like a little extra phosphorous in their diet to promote flowering.

You can use any of these CRFs effectively by mixing the fertilizer into the soil or by making small holes into the soil with your finger and pouring the fertilizer into the holes. Covering up the fertilizer will slow down weed growth, and the fertilizer is more effective when it is covered up than exposed to sunlight. In almost any case, using a CRF is better than using no fertilizer at all. Placing the fertilizer in the soil at the bottom of a planting hole is another effective way to deliver fertilizer without exposing the fertilizer to weed incursion, and the fertilizer stays put in rainstorms. Experiment with some of these products and you'll be a believer as I am. Once you know how the products work, you'll wonder how you ever got along without them.