FERTILIZING YOUR TREES AND SHRUBS

                                                                                              BY BRUCE ZIMMERMAN

    We have all over the last few years seen the effects of very dry weather on our plants.  Our trees have shown a general lack of vigour.  The symptoms of this lack of vigour are smaller foliage oven stunted, twisted or cupped and sometimes there is a summer shedding of these effected leaves.  In autumn these plants may also develop their autumn colours earlier than normal.  It should also be noted that plants under stress will usually produce an over abundance of fruit.  The cause of these symptoms is a drying up of their root systems.  The environmental stress on these plants can be further aggravated by a wet season which then encourages the dried up root system to rot.  In short the consistent and timely applications of water and fertilizer avoiding the feast and famine approach will 
produce stronger, healthier and hardier plants.

    It is always good to start out with a soil test before you begin fertilizing your plants.  This will allow you to see what is missing, what is present and in what amounts.  For example, too much phosphorus (N P K ) will tie up the Iron (Fe) and Zinc (Zn) in the soil.  The lack of Iron will cause a yellowing of the leaves called chlorosis.  Iron is also a catalyst for the plants ability to use Nitrogen (N) and produce chlorophyll.

    The first method of fertilizing trees and shrubs is broadcasting.  It is quick and easy just broadcast the fertilizer over the ground around the perimeter of the plant.  The fertilizer is not incorporated into the soil so much of the nitrogen is lost in a gaseous form into the air.  This also encourages shallow rooting.  This is a serious problem with tree roots in turf areas. Shallow rooting makes a plant susceptible to drought, cold, heat, compaction and physical injury.  If you do use this method then water well but not excessively afterwards.  If there is turf under these plants then the entire turf area must be fertilized to provide a consistent colour and rate of growth.  The fertilizer is also not applied within two to three feet of the trunk of a tree.  This method is not used on slopes where runoff is a problem.

    Subsurface fertilizing is used where runoff is a problem or where the turf or groundcover under a tree can not tolerated the heavy load of fertilizer required by the tree.  The first method of subsurface fertilization is the application of granular fertilizer in drilled or punched holes situated in a zig zag pattern evenly spaced around the drip line of the tree (perimeter of the branches).  The holes must be made deep enough that the turf in the immediate area is not burned or receive more fertilizer than the rest of the turf.  If it is  not you will have circles of excessive growth or dead patches.  Using the liquid injection method for subsurface fertilization allows you to water deeply at the same time.  The liquid injection method of subsurface fertilizing is evenly distributed in the area starting two to three feet out from the trunk and extending out to the drip line of the tree.  Do not over water to feed the plant and never fertilize a plant in moisture stress.  You must water well but not excessively at least one day before you fertilize.  In both of these methods the fertilizer should be applied to a depth of at least eight to eighteen inches. 

    Newly planted trees and shrubs have some special needs.  First ask the nursery person when and what they were fertilized with.  If it can be seen and removed do so.  Do not throw it away reserve it.  Good examples of these are pills, tablets and prills.  Use a transplant fertilizer with a rooting hormone after planting.  The reserved fertilizer is evenly distributed in the soil mix going back into the planting hole.  The reason is if a plant is to establish itself into the native ground there has to be a reason to leave the rich comfy home of the original container mix and continue to move ever outward.  

RATES AND TIMING

    Dormant feeding of established trees and shrubs with a granular fertilizer is a good idea as it allows time for  the fertilizer to start to work.  Using a recommended fertilizer that suits the needs of both the plant and the soil fertilize according to the label directions.   Generally for shrubs you will broadcast a granular fertilizer in early Spring at a rate of half to two pounds per hundred square feet.  Obviously this is a guesstimate and will vary with the numerous different parameters.  Trees in an area where there is turf you will apply a spring application when the turf can utilize it.  If the tree requires more than the turf can handle then split your applications with the second one occurring some five to six weeks later.  Generally you will broadcast a granular fertilizer at a rate of six to ten pounds per thousand square feet.  Always apply the fertilizer your plant needs following the label directions.  Deep root fertilization with liquid fertilizers is done in Spring ensuring that you do not over water.  The liquids are applied to a depth of eight to twelve inches for trees and four to six inches for shrubs and flower gardens.  Remember to always follow the label directions.

    Another method of fertilizing a plant is through it's leaves.  Foliar feeding is used when a quick fix is necessary.  You maybe applying a single nutrient or a full compliment of them directly to the leaves.  This is quite quick and fairly efficient.  The liquid fertilizer can be applied after the foliage is hardened off in the Spring and up until August in this area.  Precautions should be taken to prevent burning especially during periods of drought or high temperatures.  Always follow the label directions.

    The last way of fertilizing your trees and shrubs is the tree stake method.  This is the easiest and hence the most popular method with home owners.   The fertilizer spikes are driven into the ground with a plastic cap and a hammer.  This is usually done in Spring or in very late Autumn.  The spikes are driven into the ground evenly spaced at the drip line of the tree.  The number of spikes used is determined by the caliper of the tree usually taken at eighteen inches up from the ground.  Since the manufacturers instructions do vary always follow the label directions.

   Plants are like people they do better under good growing conditions. It is important that you recognize the the signs of stress and better yet you should strive to never have a plant of yours go wanting.

Technical Bulletin (Provided by Plant Products Co. Ltd.)

Plant-Prod 30-8-8 Tree Fertilizer - 

Water Suspendible Fertilizer With Slow Release Nitrogen

Guaranteed Minimum Analysis