What is Plant Health Care? (PHC)

Plant Health Care is defined by the International Society of Arboriculture as a holistic approach to maintaining the health, growth, and long-term stability of trees and plants. Instead of waiting for visible problems to appear, Plant health care (PHC) focuses on understanding the needs of each plant, identifying early signs of stress, and addressing issues before they become serious.

The first step in any PHC program is knowing what you’re working with. That means inventorying the property and identifying every tree and plant on the site. Different species have different needs, vulnerabilities, and environmental preferences, so a clear understanding of what is growing on the property is essential. Once the species are known, an arborist can evaluate which factors might be hindering their health and growth. These can include soil limitations, nutrient deficiencies, insects, diseases, or environmental stressors.

PHC is proactive rather than reactive. When the whole ecosystem and how each tree functions within it can be understood, homeowners can preserve the health of their landscape and avoid costly interventions later.

Early Warning Signs of Tree Decline

Trees rarely fail out of nowhere. They almost always show early warning signs long before a major problem becomes visible to the average homeowner. One of the first indicators is a change in crown color. When the canopy loses its vibrant green and appears pale, thin, or patchy, it often reflects nutrient deficiencies, root stress, or declining chlorophyll production.

An increase in dead branches is another clear signal. When branches begin dying back within the crown, it means the tree is no longer able to support its full canopy. This can stem from poor soil conditions, drought, compacted roots, or disease.

The presence of insects or disease organisms is also a common warning sign, but interpreting what you see can be tricky. Many homeowners misidentify harmless organisms like lichen, with more harmful pests like bacteria and fungi. Meanwhile, truly damaging fungi or bacterial infections may go unnoticed without trained eyes. This is why early evaluation by a certified arborist is so important.

Mushrooms growing on or around the trunk or root flare are often the most serious indicator of all. Fruiting bodies like these typically signal internal decay or root rot, meaning the tree’s structural integrity may already be compromised. Recognizing these signs early allows for timely intervention, helping restore health, reduce risk, and extend the life of the tree. When you suspect a problem, it is important to have a trained arborist, like P.C. Hoag & Co. Inc., to come and analyze your tree. 

How Arborist Diagnose Tree Health Problems

A trained arborist evaluates the entire tree from the canopy down to the root flare, looking for structural defects, foliage discoloration, deadwood, insect activity, fungal growth, soil issues, and changes in the tree’s overall form. This first step often provides enough clues to understand what may be stressing the tree.

When visual cues aren’t enough and a deep look is needed, arborists take samples for testing. This can include leaf or twig tissue samples to identify nutrient deficiencies or disease organisms, as well as soil samples to assess pH levels, organic matter, compaction, and mineral availability. These tests help pinpoint the root cause (pun intended) of decline rather than just treating the symptoms. By combining visual assessment with scientific analysis, arborists can provide accurate diagnoses and recommend targeted treatments that support long-term tree health.

Common Tree Health Issues in Northern New England

Many of New Hampshire’s most iconic tree species face specific insects and diseases that can severely impact their long-term health. A strong Plant Health Care program focuses on identifying these issues early and applying targeted treatments to protect the landscape.

White ash trees are threatened by the Emerald Ash Borer, an invasive insect that has devastated ash populations across the Northeast. Eastern hemlocks face a similar challenge from the Hemlock Woolly Adelgid, a tiny insect capable of killing mature trees if left untreated. American beech trees are struggling with a combination of leaf and bark disease that weakens their structure and vitality.

Several of the region’s pines also face serious health threats. White pines are highly susceptible to blister rust and multiple needle-cast diseases, while red pines often suffer from Diplodia tip blight, which stunts new growth and leads to significant dieback.

Broadleaf species have their own vulnerabilities. Red and sugar maples can be affected by anthracnose, a fungal disease that causes leaf spots and premature leaf drop. Red oaks are at risk for oak wilt, a fast-moving and potentially fatal disease. Even white birches, known for their beauty and trademark bark, are frequently targeted by the Bronze Birch Borer.

A recent problem NH faced recently was an outbreak of Spongy Months, noted by the sudden loss of leaves in the summer time.

Fruit trees are especially prone to pests and pathogens. Apples commonly face apple scab, apple maggot, and plum curculio. These are issues that affect both the tree’s health and the quality of the fruit. Fruit trees can be especially hard to manage, which is why P.C. Hoag offers fruit tree management to local New Hampshire and Maine orchards.

Each of these threats requires a different treatment approach, making proper diagnosis essential. With timely intervention, many of these problems can be managed successfully, helping preserve the health and longevity of New Hampshire’s trees.

Preventing Disease and Decay

The best way to prevent disease and decay is to make the tree healthier from the ground up. Most problems start in the soil, so improving soil conditions is one of the most effective steps a homeowner can take. Adding minerals and organic matter where needed helps boost nutrient availability, support root growth, and strengthen the tree’s natural defenses.

Allowing leaves to remain on the ground is another simple but powerful tool. As they break down, leaves create an organic layer that improves soil structure, feeds beneficial microorganisms, and returns essential nutrients back to the root zone. For this reason, it’s best to avoid growing grass right up to the trunk. Turf competes aggressively with trees for water and nutrients, and it prevents the natural buildup of organic material around the base.

Planting shrubs and reducing large areas of turf also help create a healthier ecosystem. Shrubs, perennials, and groundcovers contribute organic matter, retain moisture, and reduce soil compaction. Increasing the diversity of native plants on a property strengthens the entire landscape by creating a balanced environment where pests and diseases have a harder time taking hold.

Healthy soil leads to healthy roots, and healthy roots lead to resilient trees. By supporting the ecosystem around them, homeowners can dramatically lower the risk of disease, decay, and structural failure.