Landscape Architect Articles

LSMP Tree Care April 2006 Fertilizing for Tree Growth and Health03-30-06 | News

Fertilizing for Tree Growth and Health

By Don Eberly and Jeff Collard, Eberly Public Relations Photos courtesy of Eberly Public Relations and Skinner Nurseries.

Slow release fertilizers provide trees essential nutrients they need during both the initial growth stages at the nursery level and throughout the entire life cycle in the landscape. Fertilizer is generally best applied once per year for young trees and once every 3 ?EUR??,,????'??? 4 years for established landscape trees. Soil fertility testing throughout the life of a tree helps determine precisely how often fertilization should be implemented.

Careful soil nutrition should not end when trees say goodbye to their containers.

Bruce Hammersmith is passionate about marrying modern practices with traditional tree care. The general manager of Florida-based Skinner Nurseries is quick to point out that in the three years since the company started using computer software as a soil nutrition and tree growth management tool, the results are measurable.

?EUR??,,????'??Before we implemented the use of our software, we were getting 1 inch of caliper growth per year, which was pretty good. Now we?EUR??,,????'???re seeing 1.5 inches of caliper growth per year, which is incredible. We?EUR??,,????'???re growing trees faster, without sacrificing quality,?EUR??,,????'?? he said. The nursery is getting a more uniform crop, a better quality product, and a higher return on investment. And in an industry where scrap rates are historically high, Skinner Nurseries has a rate closer to zero.

Tree fertilization practices ?EUR??,,????'??? whether for trees in containers or the landscape ?EUR??,,????'??? yield far better results when they are based upon a systematic approach as opposed to guesswork. Scheduling fertilization from seedling to high caliper is a critical element to successful tree health, as are the correct amounts and types of fertilizer.

But Hammersmith hastens to add that while Skinner?EUR??,,????'???s process control software is an extremely useful tool, it does not take the place of good growing practices.

The software, which was originally designed for machine maintenance in factories, stores input data and then acts a reminder for daily or even hourly maintenance needs.

It also acts as an early detection system for soil nutrition deficiencies or overloads, and for other factors such as nutrient leaching.

To improve and refine the soil nutrition management software, the nursery recently hired a full-time Doctor of Plant Medicine, Dr. Javier Garces. He trains growers, contractors and superientendents alike about the importance of soil nutrition management.

Garces is responsible for refining the technical horticultural specifications for the process control software, and he is immersed in a study of container types and container soil mixes with respect to factors such as water and fertilizer retention and filtration. Garces was in the first graduating class from the University of Florida?EUR??,,????'???s Doctor of Plant Medicine program, which is in turn the first such program in the United States.

A tree that is administered a precise and timed fertilization program will perform well and remain a vigorous grower in the landscape. Florikan?EUR??,,????'???s Nutricote 540-day CRF is one way to feed trees the nutrients they need over time, because its long-term poly-coated components release nitrogen, phosphorous and potassium at precisely the correct intervals and are not adversely affected by temperature or rain.

When Trees Leave the Nursery

Once trees leave a nursery, continued strategic attention by landscape contractors is necessary for the trees to successfully transition from the container to the landscape. This clearly requires ?EUR??,,????'??out of the box thinking,?EUR??,,????'?? but is a necessary component to any landscape development or maintenance program. According to experts, three important factors for tree establishment are correct planting, irrigation, and fertilization. Hammersmith offers the following tips:

Correct planting. When planting a tree, spread all roots radially outward (like the spokes on a bicycle wheel) and downward. If there are any encircled or inward-facing roots, work them out of the root ball and reposition them. For correct planting depth, locate the point where the top-most root emerges from the tree trunk and place this slightly above the surface of the surrounding landscape soil. The number one reason for tree failure is planting too deeply.
Irrigation. Regular irrigation after planting encourages root growth, facilitates rapid establishment, and helps maintain a dominant leader in large trees. Recently planted trees do best with light frequent waterings. As a rule of thumb, a 2-inch caliper tree should be watered daily for two weeks, then every other day for 2 months, and then weekly until established. The goal is to keep the soil moist, neither overly wet nor too dry.
Fertilization. Trees need plenty of nitrogen for good growth, so Hammersmith suggests applying fertilizer according to a regular schedule. Select a high quality fertilizer that is low in salts. Read fertilizer labels and choose one that contains less than 1 percent chlorine.

According to Hammersmith, adequate soil nutrition plus the right balance of air and moisture in the soil are the two keys to tree health care. The reality is simply that this basic recipe is often forgotten when trees make their way into landscapes around the country. ?EUR??,,????'??If you get nutrition right and if you get the air-moisture balance in the soil right, the trees are going to grow really well,?EUR??,,????'?? he says. For growing trees in the landscape or ?EUR??,,????'??in the box,?EUR??,,????'?? this recipe for success, honed over the years, is right on the mark.