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Long before there were arborists and landscape architects, trees and plants grew vibrant and healthy with little to no assistance from humans. So why do we fertilize our plants and trees now, when they have been growing successfully on their own for thousands, even millions, of years?

Fertilizing your trees without growing your budget

By Nicole Slaydon

 Long before there were arborists and landscape architects, trees and plants grew vibrant and healthy with little to no assistance from humans. So why do we fertilize our plants and trees now, when they have been growing successfully on their own for thousands, even millions, of years?

Unfortunately, urban sprawl and continuous development often has a negative impact on the natural environment of trees and plants. Housing and commercial developments, side-walks and paved roads, and damage from droughts and other natural and manmade disasters can result in diminished nutrients in the soil, reduced surface areas for root systems, and limited access to water and other stimulants necessary for trees and plants to thrive.

Luckily, in the past 100 years, we found a way to correct the inadequacies we’ve caused in nature and the soil with advanced fertilizing technologies. We may not be able to undo all the damage, but with a bit of know-how and superior fertilizing practices, your trees and plants can thrive in today’s challenging environment.


Back to the basics – what kind of fertilizer do I need?

Like all living things, plants depend on several different elements to grow. Most basic fertilizers are primarily comprised of a plant’s three major nutrients: nitrogen, phosphorus and potassium (N-P-K). In addition to these elements, you can also find secondary plant nutrients, such as calcium, sulfur and magnesium, in most basic fertilizers. Premium fertilizers can also add copper, zinc, manganese and iron.

Organic or biologically based fertilizers also include other components that represent the best of nature itself, such as mycorrhizae and beneficial microbes. Mycorrhizae are specialized fungi that form mutually beneficial relationships with plant roots and trap minerals, nutrients and water to help promote plant growth and health. Beneficial microbes are specific and naturally occurring microbial strains selected for their individual contribution to plant performance. They are included in biological fertilizers to improve the color of plants, increase nutrient uptake, and improve root density and mass.


Fertilizing methods – the when, how, and where

No matter what kind of fertilizer you use, getting the right nutrients to the tree roots is the most important task. One very effective method is to use a controlled-release fertilizer; this type can be a granular fertilizer that is either sprinkled onto the soil near the root ball or dug into the soil before planting.

“Use controlled-release fertilizer once or twice a year,” said Kristi Woods, Roots Plant Care senior scientist. “These fertilizers are easy to apply, and work best when you want a slower release of nitrogen.”

If you’re looking for a quicker response, a soluble — or liquid — fertilizer will give you visible results faster than a slow-release granular. One of the most effective ways of applying a soluble fertilizer is through injection feeding. A special injection “wand” or “rod” with a garden hose attached to it is used to inject the fertilizer and water directly into the tree root zone.

“For the best results, start close to the tree and move out in a grid-like pattern until you reach the drip line,” explains Woods.

Woods recommends using a soluble fertilizer when you see visible signs of stress such as small or yellow leaves, loss of leaves too early in the year, or overall reduction of plant growth and vigor.

As for timing, fall fertilizing can add a much needed boost if you’ve forgotten in the spring, when fertilizing is most effective.


Common (mis)assumptions

First and foremost, Woods notes that in her experience, the worst assumption people often make about fertilizing is that it is not necessary.

“I think most homeowners believe once the tree is planted and living, it’s the best it can get” she explains. “Fertilizing on a regular basis will improve the tree, and most times you’ll see that improvement in the same season — especially if you fertilize in the spring.”

Furthermore, you’ll continue to see additional benefits for several years after you begin fertilizing.

“Other benefits from fertilizing, such as a taller, larger tree and fuller canopy, become more obvious as the years go by,” she said.

Woods also warns that herbicides used on lawns can negatively impact trees. Most herbicides are targeted to broadleaf plants like trees, and can also build up in the soil over time. Leaf curling, disfiguration and discoloring are signs from the tree that there is an excess amount of herbicides in the soil.


Tips for healthy trees on a tight budget

As the world scrambles for ways to off-set the rising costs of, well, everything, arborists are also looking for ways to keep trees healthy and vibrant while keeping costs to a minimum.

“Applying a general lawn fertilizer may be effective enough fertilization for your trees,” Kristi Woods suggests. “A well-rounded and biological fertilizer will keep your lawn green and healthy while also giving a helpful bump to your trees.”

Woods also recommends tree spikes for those trying to cut costs because “if you’re looking for something less expensive and easy to apply, tree spikes can be applied once a year and release nutrients slowly over time.”


Being proactive about fertilizing your trees will result in healthier, more vibrant plants, and could ultimately end up saving your plants in times of stress. Give your trees the best chance at success by fertilizing at the right times, the right way, and with the right products.


Nicole Slaydon is senior communication coordinator for Roots Plant Care Group, a division of Novozymes Biologicals, Inc. For more information, visit www.rootsinc.com

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