Fall Fertilization of Trees: Do I have to?
Few things in life require a ‘have-to’ attitude. We don’t ‘have to’ run the vacuum, change oil in the car, return calls or open mail. Heck, we don’t even ‘have to’ go to work, pay taxes or pull the rip cord on the parachute, right? While these things may be valid suggestions (and good ones), we can get by – albeit for a short time – without doing them. And we all know people who actually don’t do some of these things, right? Well, maybe not the parachute thing....
THE NEED FOR NUTRIENTS We humans can eat well to gain every opportunity to give the body what it needs. But no matter how careful one is, deficiencies exist. And so there are supplements – vitamins – that round out the function of the body to allow it to perform at optimum levels. Your trees, however, don’t have the luxury of choosing their diet. They may have been planted there by you or a previous homeowner ages ago and they get what they get: what’s in the soil and whatever water comes along. If we want them to manifest a healthy canopy, develop strong root systems resistant to decay, grow well-attached limbs and become all of their potential, they need supplements too. Your Certified Arborist is trained to know what’s needed and when, so as always, they are an invaluable resource for you.
MACRO- AND MICRO-NUTRIENTS
Like the name implies, Macronutrients are needed by trees and shrubs in larger amounts. Things like Nitrogen, Phosphorous, Potassium, Calcium, Magnesium and Sulfur. When the soil is deficient of these critical additives, the results are visible: Slower growth (sometimes very significant), malformed or undersized leaves or early leaf drop…these are all pretty much in your face and shouldn’t be ignored. Micronutrients on the other hand – Iron, Copper, Zinc, Chlorine and Boron – aren’t as detrimental or telling. Lack of Iron, for example, will cause yellowing of the leaves between the veins. All fertilizer labels will indicate the amount of each nutrient (for example 9-18-9 indicates the amount of Nitrogen, Phosphorous and Potassium – by weight – in this mix) and can come in a dizzying array of combinations. If you’re doing the fertilization yourself, grab a soil test from the Lehigh County Penn State Extension or Northampton County Penn State Extension. That way you’ll know what you need. If you’re hiring a professional, they’ll know what’s needed for your area…heck, they dream about this stuff :)
HOW DO I APPLY? While most homeowners may be unwilling or unable to do much more than mix the store bought chemical fertilizer and apply with liberal amounts of water (and keep watering), if care was taken in diagnosing, selecting the fert and applying it properly, splendid results can surely be had. Professionals have a bit of an advantage here, as they can trench the root area and apply directly for maximum uptake, or they can inject the tree for ultimate effectiveness. Check out the cool tree injection pic. REMEMBER A FEW THINGS… If, through research, it’s discovered that the soil pH is above the optimum level for your tree or plant species, further intervention will frequently be necessary to avoid things like interveinal chlorosis (a yellowing between the veins of the leaves). Chlorosis indicates poor iron availability in the soil. There’s enough iron there, but the tree can’t take it up and use it effectively. To fix this, the pH of the soil may be lowered (long term solution) or iron chelate may be applied to the leaves or soil to enhance absorption. Kinda like how Vitamin D enhances Calcium absorption in humans. It’s all about bio-availability, you know?
And lastly, remember that fertilization is a balancing act. Too much, too little or the wrong kind will negatively impact the growth and health of your trees and shrubs. But by all means, DO fertilize. The right amount will have them smiling down on you as you smile up at them!
