Real Care for Trees
Join us as we take a deep dive into real care for urban trees. Real solutions aimed at promoting tree health.
The condition of soil is often overlooked when trees show signs of stress. The reality is, most of our urban soils constitute a poor environment for tree growth. Compacted, or poorly structured soil, reduces a tree’s ability to absorb water and essential elements, reduces fine root growth and limits gas exchange (Oxygen and C02) between the root system and the atmosphere.
The good news is that there are solutions to amend poor urban soil around your tree without injuring it. A supersonic air spade can be used to excavate trenches radially around the tree, that is, in a spoke pattern. Twelve- to fourteen-inch-deep trenches are subsequently backfilled with a mix of the native soil and amendments. These amendments increase pore space in the soil, promote a better root environment, improve water holding capacity, increase gas exchange to the atmosphere, and promote microbial activity in the soil. Trees are far removed from their natural forest habitat and often show varying degrees of stress in the urban setting. Amending the soil to a more ‘forest like’ condition is probably the best thing that can be done for a tree in the city.
Root Collar Excavation/Root Pruning
Fertilization and Health
Urban soils often lack the organic top layer found in the forest. Leaf litter and the breaking down of organisms generates essential elements that trees need to grow and thrive. Nutrient poor soils can be fertilized to add essential elements that are lacking. Yellowing and small size of leaves can be signs of macro or micronutrient deficiency. Our method of choice is liquid injection, sometimes called deep root fertilization, which supplies the dose of fertilizer mixed with water directly to the root system of the tree. Since not every tree needs high doses of fertilizer, but most trees can benefit from a lighter level of nutrient dosage, we also inject liquid kelp which is very beneficial to fine root growth and microbial activity in the soil. Both trees and hedges can be deep root fertilized to help achieve landscape goals. When it comes to higher doses of fertilizer, we send soil and foliar samples to a lab first to ensure that the right type and amount of essential elements are being added to the soil.
Montreal is home to some exquisite Magnolia trees; however, Magnolia scale is often a big problem. The scale attaches itself to the twigs of the tree to feed on sugars just beneath the bark. The scales excrete honeydew which attracts wasps, which can actually become quite the problem near walkways and pools. Natural Horticultural oil, diluted in water, can be sprayed on the entire tree just before bud break, or after the leaves have fallen. The oil disrupts the life cycle of the scale and is effective in controlling it. It is important to achieve full coverage of the tree, which is why we use our spider lift in most cases to spray the tree from above.
It is important to note that the scale is likely a secondary issue, and is only present on the tree because it is already being affected by primary problems. While treating the scale can achieve short to medium term goals, identifying and trying to correct primary issues is of great importance in the medium to long term.
The weather in Montreal seems to get hotter and dryer with each passing year. Many trees that previously grew very well in our climate are beginning to struggle. In extended periods of little or no rainfall in the heat of summer, the soil can be injected with water to bring it back to field capacity, or replenish its available water reserves. We use commercial grade pump and injection equipment to efficiently deliver the water to where it is needed most.
Newly planted trees need constant irrigation for the first growing season since their root systems are contained to a very small ball that dries out very quickly. We provide all newly planted trees with Gator bags (water bags) that slowly deliver water to the root ball and only need periodic filling.
Structural Pruning of Young Trees
Proper structural pruning is one of the most important, yet most overlooked practices in tree care. What is structural pruning? It’s the guidance, through pruning, of tree growth over a number of years to produce strong structure. The pruning focuses on promoting small branch to trunk aspect ratios, typically making sure that branch diameter is a maximum of half the trunk diameter at its connection point. Weak branch connections are located and dealt with accordingly before they have a chance to become dangerous or likely to break. The process begins at planting and should be carried out every two to three years. The first permanent branches can be located in the early years, and lower branches can be gradually removed while they are small in order to avoid massive removal cuts in the future. The benefits of early structural pruning are many, but here are a few:
- Keeps pruning wounds small and spread out over a number of years
- Avoids huge pruning wounds later on that the tree can’t compartmentalize (wall off)
- Spreads maintenance costs into smaller amounts over a long period of time
- Creates a stronger, safer tree structure
- Minimizes the odds of costly interventions regarding tree safety later
- Keeps the arborist coming back to the property on an ongoing basis, leading to early detection of potential health or site problems.
The structure of more mature trees can be gently modified with good pruning, but the time to act, and keep acting, is when the tree is young, dynamic and vigorous.
Cabling and Bracing of Trees
In the urban setting, trees with defects can make for a dangerous situation in zones with high occupancy, such as yards, driveways, sidewalks, paths and roadways. Since removal of mature trees is rarely an option, mitigating the risk to acceptable levels is imperative. The most common tree failures are due co-dominant stems tearing apart at their weak attachment point. What is a codominant stem or branch? A codominant stem occurs when two or more equal sized trunks or branches grow tightly together. When this happens, the physical connection of parts tends to be very weak. The presence of included bark (bark that becomes crushed between stems) further compromises the connection. Thankfully, the risk that these weaknesses present can be substantially mitigated by proper cabling and bracing of tree parts.
Generally, if a codominant union has included bark and is showing a crack, we will brace the tree at the faulty union with multiple steel rods. Anywhere from two to ten rods could be installed depending on the severity of the weakness and size of the tree. In addition, a steel or dynamic (rope) cabling system is installed in the upper canopy of the tree according to industry best management practices and manufacturer specifications. All of our systems are designed according the unique demands of each tree. Some trees require only a cabling system, and no bolts. In every case, we always recommend end weight reduction of heavy tree parts before any system is installed. All systems are personally inspected by us on a yearly or bi-yearly basis to make sure that they are performing correctly.
The physical, chemical and biological properties of soil have a massive impact on tree health and longevity in the urban landscape. We strongly recommend proper soil testing and analyses before planting new trees and before fertilizing older ones. We can collect all the samples needed to provide a report on the properties of the soil around current or future tree plantation sites. A soil report contains:
- Soil Texture
- Bulk density
- Organic matter content
- Cation Exchange Capacity (Nutritional Elements)
Knowing what the soil properties are on a site can provide information as to which tree species will thrive, why current trees may be stressed, soil compaction and water holding capacity. In addition, information on soil texture and bulk density helps when creating a proper irrigation schedule for trees.
Trees and Construction
Trees are almost always overlooked when construction, renovation or major landscaping occurs. Most often they are an obstacle to tradespeople, and trades in general have little idea of the injury they can and do cause trees. Direct injury to tree trunks and major branches is permanent, and even though the tree will compartmentalize and grow over some wounds, these points often lead to cracks, cankers, infections and pests. On a site with trees, the time to act is before any work begins. We firmly believe that consultation with an arborist is vital before work begins, and that a tree protection plan should be put into place. The most common injury to trees is to the root system from either severe compaction or cutting of a large percentage of roots. This can be avoided by setting up tree protection zones under the trees that surround a designated portion of the root system. These zones are usually fences and effectively seal off the area from foot and vehicle traffic. A site meeting may also be scheduled with the arborist in charge to brief construction or landscape trades. All too often, we show up and irreparable damage has already been done to mature trees.
Proper assessment of tree risk requires diligent, meticulous investigation of the tree and of its growing site. A proper tree risk assessment should include all details pertaining to tree parts that are or will be a risk to people and property, and outline a plan of action to mitigate those risks to acceptable levels. This could include pruning, cabling and bracing the tree, removal of the targets or even the removal of the tree. There are three types of assessment:
- Limited visual assessment
- Basic assessment
- Advanced assessment
Limited Visual Assessment
A limited visual assessment is the most cost effective, but is usually used for larger populations of trees. If a property has dozens of trees, this method can quickly provide some information on their general condition.
A basic assessment will be more in depth and will involve photos, binoculars to inspect details in the crown, a probe and mallet to check for lower cavities, magnifying glass to look for fruiting bodies or insects and perhaps a small shovel to uncover the root crown. This is the inspection we conduct on the most regular basis and will always be paired with a plan of action.
In the event that specific details of note arise in a basic assessment, more advanced diagnostic tools may be required to properly assess tree risk. An advanced assessment will include any of the following:
- Inspection of the canopy with a drone
- Climbing the tree for a detailed inspection and photos/samples
- Root collar excavation with supersonic air spade to inspect for root rot and issues
- Tomography (scan) to look for cavities and decay with the tree
- Resistance drilling to verify tomography results
- Laboratory analyses of fruiting bodies
All types of assessments are paired with a written report with corresponding photography and test results.
- Apply a thickness of two to four inches of mulch, but not more
- Make sure that mulch isn’t touching or piled around the tree trunk in any way, this holds moisture against the root collar, gives a spot for rodents to hide and chew on bark, and generally creates a more suitable environment for rot and disease.
- Never install geotextiles or plastics under mulch as they inhibit gas exchange and water permeability in the soil.
- Use good quality arborist woodchips with plenty of green leafy material. The elements contained in the leaves will disperse into the soil around the tree.
- Avoid decorative mulches such as lava stone, dyed woodchips, rubber, river rock or other recycled materials, as they offer no benefit to the tree or soil. These types of mulches may even harm the tree by generating more heat and drawing more water out of the soil.
- Mulch as big of an area as is feasible, ideally to the outer edge of the canopy.
- Lowers soil temperatures considerably, reducing water evaporation and increases soil water retention.
- Eases compaction of the upper layers of the soil around the tree.
- Becomes rich in organic matter and supports beneficial fungi and organisms.
- Reduces the amount of fall cleanup and grass to mow.
- Removes grass, which competes strongly for resources with the fine absorbing roots of the tree.
- Removes the likelihood of lawn mower and trimmer damage to the trunk and exposed roots of the tree.
- Creates a beautiful, natural look in the urban landscape.