What Is Plant Health Care for Trees?

Some people hear “plant health care” and picture a truck that sprays everything on a schedule. That is close to the opposite of what it means. Plant health care, often shortened to PHC, is a way of managing trees and shrubs so they stay healthy enough to hold off most problems on their own.

The idea is simple. A healthy tree in good soil defends itself better against insects and disease than a stressed one. So most of the work goes into the conditions the tree lives in, and treatments are used when there is a specific reason for them.

In my opinion, the most useful thing a PHC program does is answer the question “why?” A tree with thin leaves, dead twigs, or bugs on it is showing a symptom. The symptom is usually not the cause.

Every program should start with someone looking closely at the tree and the ground around it. What I look for is the whole picture: the crown, the leafy top of the tree; the trunk; the root flare, where the trunk widens into the roots at the soil line; and the site itself.

• The tree. Leaf color and size, dieback in the top of the crown, wounds, cracks, fungus, and signs of insects.
• The site. Compacted soil, fill dirt piled over roots, recent construction, turf grown up to the trunk, sprinklers hitting the bark, and drainage.
• The history. When the problem showed up, what changed in the yard, and what has been sprayed or spread nearby, including lawn weed killers.

Our arborists often pull a soil sample at the start, so the plan is based on what the soil test shows rather than a guess. A diagnosis can take more than one visit when the cause is not obvious. Our plant health care service page walks through how we set up a program from that first visit.

Integrated pest management, or IPM, is the pest control side of plant health care. The U.S. Environmental Protection Agency describes it in four steps.

1. Set an action threshold. Decide ahead of time how much damage or how many pests justify doing something.
2. Monitor and identify. Find out exactly what the insect or disease is. Many insects on a tree are harmless or even helpful, and treating the wrong thing wastes money.
3. Prevent. Use the right plant in the right place and good cultural care, meaning the everyday growing conditions, so pests have less to work with.
4. Control. When control is needed, start with the least risky method that works. Broad spraying of products that kill many kinds of insects is a last resort.

In practice that means a few scale insects on one shrub may only need watching, while an insect that is killing branches may need a targeted treatment. That is a decision you and your arborist make together after looking at the plant.

Most of a tree’s roots sit near the surface. UF/IFAS extension in Hillsborough County notes that most tree roots in our region are within 2 to 4 feet of the surface. That is where a lot of PHC work happens.

Construction and grading often strip away the top layer of soil and pack down what is left. Roots grow fast in soft soil and slowly in compacted soil. When the soil is the problem, fixing it may have to come before any treatment will help.

Mulch is one of the simplest tools we have. UF/IFAS recommends a layer about 3 inches deep after it settles, kept at least 12 inches back from the trunk, in a circle at least 8 feet across. Mulch piled against the trunk like a volcano keeps the bark wet and can cause problems of its own.

Watering. Light, frequent watering does little for an established tree. During a long dry spell, UF/IFAS extension advises watering slowly under the whole canopy, about one inch of water every two to three weeks. Newly planted trees are different and need water much more often until their roots spread out.

Fertilizer. Established trees often find what they need through their wide root systems. According to UF/IFAS, adding fertilizer to a healthy mature tree may not accomplish anything, and feeding a tree that is stressed for other reasons can do harm. When a deficiency is suspected, the advice is to test the soil or the leaves first and then treat what the test shows.

Pinellas County also limits fertilizer. No nitrogen or phosphorus may go on turf or landscape plants from June 1 to September 30, and phosphorus is not allowed unless a soil test shows the soil is short on it. A soil test protects your trees and your money, and it keeps us inside the rules.

When a specific problem does call for a product, the goal is to use the narrowest one that fits. Depending on the problem, that might be a soil treatment to correct pH, a trunk injection for a particular pest or disease, or a spot treatment on the plants that have the problem instead of the whole yard.

Some problems have no proven treatment at all. Ganoderma, a fungus that decays the lower trunk and roots, is one example. In those cases, PHC is about careful monitoring and planning, not selling a product that will not change the outcome.

PHC is also not the first step for every tree. A tree that is dead, or one with a serious structural defect, needs a different conversation. If you are not sure which camp your tree is in, our page on whether a tree is dangerous covers the warning signs.

A good program is written down. It says what the arborist found, what the goal is, what will be done, and why. Each visit gets checked against that plan, and the plan changes if the tree responds or something new shows up.

How often someone visits depends on the property and the goal. A yard with a few established oaks needs far less attention than an estate with many specimen trees and ornamentals. If a tree does not need a program, I would rather tell you that than build one that will not produce results.