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Essential Tips for Year-Round Tree Health

If you are reading this, you are most likely a tree lover and would do anything in your power to keep your leafy children happy and healthy. Trees or shrubs in general require a few key things to live and thrive.


It all starts with the planting process, but I am going to assume that you have already planted your new baby and are now looking for tips and tricks on how to make it thrive. Or, you have inherited one or a few old giants and are looking to care for them so they can carry on telling stories for many generations to come. There are some subtle differences in caring for young trees versus caring for older established trees.



Water management:

Water management the most important factor for tree health, above all else. The most common mistake that we see is the over- and under-watering of trees. There are very scientific methods for determining the water need of trees, such as calculating the water use efficiency which takes into consideration the transpiration rates and photosynthetic rates of a tree.


The most important aspect you should consider is the type of soil in which your tree is planted, whether it be sandy, loam or clay soils will determine how much water and at what frequency is needed. Sandy soils will require regular watering, and generally have a fast infiltration rate (how fast water is taken up by the soil), compared to clay rich soils which bind water strongly and will need less regular watering, but can easily become waterlogged and create all sorts of other issues for your tree.


Depending on the type of soil you have identified, it is important to implement an irrigation schedule of sorts that will accommodate most of the plants in your garden. Generally young trees will need water three to four times per week, as they need to establish their root system to look for water sources.


Older trees (eg. Old Oak trees) generally do not need irrigation as their root system is well established and most likely reach deep into the underground water network. Old trees generally have less vegetative growth and therefore have a smaller demand for water, compared to young trees which might double in size every year.



Your next question might be “How do I know if I am giving enough water?”. Again, there exists multiple scientific methods for determining the water holding capacity of a soil together with the transpiration rate of a plant, etc. However, an easy method that can be used is called the “hand test” and works as follows: Select a depth that you want to test and use either an auger or a shovel to collect a sample that you want to test for moisture content.


Firmly squeeze the soil into a rough sausage shape in your hand. Observe the soil texture, firmness and roughness of the soil, water glistening, looseness of soil particles and soil/water staining on the fingers. Now estimate the moisture content as a percentage of total moisture. If water is freely running from the sample, it is generally too wet and conversely if the soil particles do not stay together and no excess water is available, the soil should be regarded as too dry. This technique requires constant evaluation to determine an accurate estimation of soil moisture content.


If all variables regarding soil moisture are satisfied, we can discuss soil moisture retention by means of mulching or cover crops. Mulching refers to the use of materials, whether natural (straw, bark, etc.) or not (plastic coverings, etc.) to keep water from evaporating out of the soil that is exposed to the atmosphere. Planting cover crops is probably the easiest method of retaining soil moisture.


Cover crops are any low growing grasses or plants which are generally planted to increase water retention and lower overall soil temperature, thereby limiting water evaporation from the soil. By selecting cover crops of the legume family, we can make use of their nitrogen fixation abilities to increase the nitrogen content of the soil.



In the opposite case, where soils have too much moisture, whether it be a shallow water table or a constant supply via irrigation, trees and other plants also suffer as these waterlogged conditions do not allow oxygen to reach the roots which is critical for cellular respiration and life.



In such conditions drainage needs to be considered. The installation of drainage is not as straight forwards as merely putting a pipe underground and hoping for the best. It is best to consult a professional when it comes to drainage as soil type, aspect, slope and many other factors need to be considered when installing drainage.


Nutrients:

All trees need nutrients to live, grow and thrive. Plant nutrients are grouped into two groups: Macro plant nutrients and Micro plant nutrients. Macro plant nutrients are needed in higher volumes than micronutrients, hence the name. Macro nutrients are Nitrogen, Phosphorus, Potassium, Calcium, Sulfur and Magnesium.  Micronutrients are Iron, Boron, Chlorine, Manganese, Zinc, Copper, Molybdenum and Nickel.


Plants need these nutrients in varying quantities and at different physiological stages to complete their lifecycles. Generally, most soils have these nutrients available for the plant to use, however many factors such as soil composition, soil pH, moisture content and others influence the availability of nutrients to plants. Liebig’s law of the minimum is important to understand, as it states that a plant’s growth is limited by the nutrient element which is deficient. Thus, if all other elements are present, except one, that one element will limit growth until it is replenished.



Generally, if you are not producing fruit commercially, and your tree does not show any visible signs of deficiencies, it is not needed to fertilize your tree. However, for your tree’s wellbeing it is recommended that you fertilize a tree at least once during the growing season so as not to limit available nutrients.


Inorganic fertilizers are fantastic in the commercial sense, as trees use more nutrients than can be replaced, and supplying inorganic fertilizers in the correct amount will support this type of production. However, in an organic, non-commercial setup it is advisable to fertilize your tree with a good compost once a year to sustain a healthy root and shoot system. Compost will increase the carbon content of your soils, promoting nutrient uptake, increasing biological activity in soils and creating a healthy ecosystem for growth.


Pruning:

Next to the correct soil moisture content and sufficient nutrients, pruning trees are of high importance to ensure healthy trees. Through pruning we can either stimulate new growth or manipulate growth to where it is needed most. Pruning during the winter is generally accepted as a necessity for a healthy tree, for deciduous and evergreen trees.


Pruning is our most important tool to manage growth, health and aesthetics. Pruning influences growth in many ways. Through pruning we stimulate vegetative and reproductive growth, we can remove dead and/or dying limbs, we can manage diseases and elevate the overall aesthetics.



Pruning can occur during summer and winter depending on the desired outcome. Winter pruning is most often used in deciduous trees to manage vegetative and reproductive growth effectively, slight adjustments can be made in spring or early summer if necessary. We often prune evergreen trees after winter as well, before their new growth flush starts in spring, this type of prune is generally to aid in light penetration into the canopy and to aid air movement in the canopy to manage pest and diseases.



As mentioned, summer pruning is normally only when a specific outcome is in mind, such as manipulation of a flower date or to stimulate vegetative growth in a specific direction.

There are a lot of specifics when one considers pruning, as the type of pruning cut, the depth of the cut, even the angle of the cut can determine the reaction that will take place.


However, the most important tips when it comes to pruning, is to have a plan in mind, to always use clean equipment, to seal the wound that is left behind against pathogens and to monitor the resulting growth.


Pest & Disease Management:

Throughout the year, one of the most important tasks is to regularly evaluate the presence of pests and diseases in your trees. In the case of pests: Always inspect trees for physical damage, such as mice or rats chewing bark; broken or dead branches; stunted or weak growth; wood shavings; holes in the bark; or any other signs that might be significant. Pests, if caught early on, can generally be managed quite easily through the help of a qualified tree health specialist.


We have a working relationship with some of the best entomologists in the country and will help you identify the pest and supply you with possible routes for control. Plant diseases can be controlled effectively, if the appropriate action is taken as soon as possible. We have access to one of the leading plant pathology labs in the world, and our tree health specialists are well versed in the care of plant pathogens.



It is important to regularly inspects your trees to determine if any new pest or diseases have invaded your trees. As stated above in the pruning section, it is imperative to keep trees open and allow free air movement to limit the possibility of pest or diseases establishing in a tree. High humidity and moderate temperatures create the optimal climate for pests and diseases to multiply, therefore it is important to maintain good ventilation through tree.


Lastly, it is important to remove any sick or dead plant material from the immediate vicinity as this material will contain fungal spores and carriers of diseases which could infiltrate other plants too.


Plant stress, whether it be drought stress, waterlogged conditions, low nutrient availability or any other conditions that impede growth, will compound any problems existing in the plant. If there is a small, manageable population of pests in a tree, stress conditions will without a doubt compound the issue and result in a population explosion. It is therefore of utmost importance to contact your tree healthcare specialist as soon as a potential issue is observed.

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