INTEGRATED PLANT HEALTH

Integrated Plant Health

Integrated Plant Health is a comprehensive approach to plant health. It begins with planting the right tree in the right location, early pruning and scheduled maintenance pruning, soil amendments including fertilization, mulching and air spading, supports, horticultural sprays, and finally tree injections.

These practises are research based and set out by the International Society for Arboriculture. In delivering these best practices in concert, the goal is to give trees the best possible start in their life, minimize cost burden, and realize a greater net benefit for your trees.

When we speak of amending the soil, it refers to practises that improve the soil structure, chemistry, and biotic factors that are beneficial to a specific tree’s root system. This is done objectively and sometimes requires soil testing.

Trees that grow in the urban environment are presented with many environmental challenges, ranging from compacted sodic soils, nutrient deficiencies, and poor biotic soil associations, such as beneficial fungi. Typically, when we see a tree that is showing signs of distress, even in the upper canopy, the “root” cause (sorry for the pun) is usually found 6” below grade.

In a healthy tree you can expect to find a mat of fine absorbing roots that are responsible for nutrient uptake. These roots, believe it or not, need oxygen (ie. they respire). Therefore, for most species of trees, the most desirable soil structure is 50% air space and 50% soil aggregate. If soils are compacted, which is common street side, or poorly drained from frequent surface watering or changes in grade, the voids found between soil aggregate become lost and the roots are starved of oxygen.

Some soil amendments include…..

Air Spading

Soil Amendments

Air Spading uses pressurized air in order to air excavate around roots without damaging the root system. The main benefits of Air Spading from a plant health perspective are to amend the soil structure particularly in urban soils that are commonly compacted around street side. Other reasons for air spading include Root Collar Excavation (RCE) in order to expose a trees root collar. If trees are planted too low, become settled or mulch is excessive around the root collar, RCE may need to be performed.

In some cases roots develop what is called Root Girldling where the root scaffolding become wrapped around the root ball causing strangulation and poor vigour in trees. As the injury from Root Girdling becomes severe the tree will show signs that looks similar to a tree that is underwatered as nutrient uptake become more impeded. Root Girdling can be caused by poor planting practices of nursery stock or highly compacted or containerized soils. In very select cases some of the girdling roots can be pruned and excised after air excavation. This must be done judiciously as each root is responsible for nutrient uptake and anchorage. For this reason, large, girdled roots should not be pruned.

Mulching

Starting with the day a tree is planted, one of the absolute best ways to amend soil is by maintaining a 1-2” layer of natural mulch over a period years and decades. It not only improves the soil structure in the first 6-8 inches (“O Horizon”) as mentioned above, but also adds a natural source of Nitrogen, Phosphorous and Potassium in a way that is slow release and doesn’t burn the roots. Fertilizers that are in liquid form can burn the roots, but also change the pH of the soil. However, as the mulch decomposes, the organic material increases the buffering capacity. This is a good thing because extreme pH changes in the soil can affect the Cation Exchange Capacity (CEC) of the soil, causing trace metal nutrients, such as Zn, Fe, Se, Cu, and Mg to be leached or inaccessable causing soils to be depleted in these micronutrients. In Chloroplasts, the organelle in plants where photosynthesis happens, these trace metals are bound to membrane proteins or in the case of Mg forms the centre of chlorophyll. If one of these metals become depleted, the chain of events that drive photosynthesis can be hindered.

Urban Tree Works sources all their fertilizers from “Tree Help.com” which formulates their slow release granulated fertilizers to each species of tree.

Vertical mulching is the creating of holes around the base of a tree or shrub that is stressed. The holes are filled with a mixture of organic material such as compost. The back fill and aeration can dramatically improve root growth and reduce or eliminate stress caused in a lawn environment or construction damage

In addition to adding fertilizers, beneficial fungi are frequently added to the fertilizer. A group of fungus called Mycorrhizae plays an important role in the development of fine absorbing roots and in plant nutrition by increasing the effective surface area of fine absorbing roots through the fungi’s mycelium. Because they are unseen, they are often disregarded when it comes to deciding upon a cause for decline in a particular plant.

Unfortunately, non-native urban soils are frequently devoid of mycorrhiza resulting in underdeveloped fine absorbing roots shown below.

Deep Root Fertilization and verticlal mulching

In a natural habitat the leaf litter forms a duff layer on the forest floor that serves as a source of fertilizer. Unfortunately, in the urban environment the practise is to remove the leaf litter all together. Without natural inputs of Nitrogen, Phosphorous, and Potassium, urban trees often need a pulse of slow-release fertilizer in the horizon where the fine absorbing roots are found.

Fertilizer is often misunderstood and misused. Fertilizer is not “food.” Plants produce their own food in the form of sugars through photosynthesis. The minerals or nutrients supplied by fertilizer provide the ingredients needed for photosynthesis and growth. When minerals are lacking or absent in the soil, fertilizer can be added to maintain an adequate supply.

Signs that your tree may need fertilizer are poor growth: poorly colored leaves (chlorotic); leaf size smaller than normal; earlier than normal fall coloring and leaf drop; little annual twig growth; or twig or branch dieback.

The rate at which the fertilizer is applied is 2-4 lbs of N per 1000 sqft. This rate is applied to the Root Zone which 1 ½ time the diameter of the tree’s canopy spread.

Horticultural Spays and Injections

Within our urban forest there exists an ecosystem of plants and animals that are interdependent and constantly in search of resources and habitat. Most of this competition happens in equilibrium, however, in some cases, especially with newly introduced plants and animals the balance is upset and the negative affects of one introduced species can be devastating to native species of trees. In those cases, working with our partners at BioForest, we can either protect trees from the effect of certain vascular fungi, for example, or control the population of pests such as aphids, as another example.

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INTEGRATED PLANT HEALTH