Do You Fertilize "MATURE" Trees?

[SweetMK]

When I started fertilizing mature trees, the internet did not exist.
At that time, my belief was "It is my money, I can waste it as I please",,
So I started fertilizing the trees on about 2 acres, maybe 20 or so trees, I never bothered to count.

Anyways, over 30 plus years, these trees have shown a remarkable increase in health, and size.
The trees are oak, poplar, hickory,, as well as apple, cherry, etc..

Not knowing what to do, and not having the internet, I simply over-fertilized at the drip ring of these trees.
BUT, I had one oak, planted near a driveway, along with some shrubs that we planted at the drip ring of the tree.
That oak sucked 100% of the nutrients, and moisture near those shrubs. The shrubs just could not compete, and they did not survive.

After seeing that, I decided that the tree was capable of seeking out moisture, and nutrients.
I decided I would take advantage of that in my fertilizing technique.

I used a bulb planting auger, it is a mini post hole digger, that digs a 3 inch diameter hole, powered by an electric drill.
My philosophy was, that if the tree liked the fertilizer it would seek it out. If it did not like it, it would avoid it.

On a tree that was 12" in diameter, or larger, I would drill up to a dozen holes, and fill the holes with a balanced fertilizer (10-10-10)
As far as results, when I simply added fertilizer on top of the soil, around the tree, I would see stimulated grass, and weed growth.
When I added fertilizer to the 6 inch deep bulb planter holes, almost zero grass growth improvement was seen.
So, either the nutrients were simply washed away into the soil, or the tree got the nutrients.

During those years, the trees that were fertilized by the bulb auger technique seem to have grown double the diameter increase, compared to surrounding untreated trees. So, I feel my fertilizer addition has helped the trees to thrive.

(I think part of my reason for believing the drilling technique would help was that I was basically duplicating the "Jobe's Tree Fertilizer Spikes" that was popular when I started this test)

One of the things I have seen over the past couple years that reenforces my theory is an abandoned compost pile.
That pile, over 20 feet long, 15 feet wide, and 4 feet high has sat for over 10 years.
I went out last week to reclaim some of the compost, and found the entire pile was filled with tree roots along the top 10 inches of material.
Below the top 10 inches, there were no roots. Those roots knew where the most moisture, and nutrients were.
The tree roots were not waiting for the nutrients to wash down, the roots were climbing up into the top of the pile.

I have two 50 pound bags of 19-19-19 fertilizer. Soon, I will get out, and drill holes, and supplement the trees near my home, again.

What are your feelings on fertilizing mature trees?? I know it would be a "hard sell" to customers to show the benefits.
I am not doing this for a customer, I am doing this for my personal enjoyment.

Share your fertilizing info with us.

 

[Dudders]

If it looks like it's doing good, then why not?

Just be aware that too much of a good thing can be a bad thing. Years ago, we ran a horse stables here and the muck heap gradually got built out until it was right up to a mature oak tree. Horse manure is a good fertiliser, but one summer I noticed a lot of dieback of the branches of that tree and it took awhile to realise the probable cause. I shifted that heap away in a hurry, trimmed off all the dead wood
and it's been fine ever since.

Just starting to come into leaf now.

 

[ATH]

Have you ever done a soil test?

Have the trees shown signs of deficiency? Have neighboring trees in similar circumstances shown signs of deficiency?

My thoughts on fertilizing mature trees: what am I going to give them that they didn't have for the previous XY decades? Unless something changed in the soil or there are identified deficiencies, I think it is a waste of time and money. If they do need fertilized, I think it is a waste of time and money to do it without knowing what they need (soil and/or plant tissue test).

 

[Dudders]

No, never tested the soil, but I wouldn't know what I'm looking for anyway! The bad news for this tree is that it's always had a concrete road around half of it - that is, for at least 80 years. But whilst that sounds grim, it's always seemed fine, and of course there are many street trees completely surrounded by hard surface that still thrive. I guess they get nutrients from the water that's constantly rising from below and which has previously washed down through the surface layers elsewhere. Think I'll let it be.

 

[sb47]

When I started fertilizing mature trees, the internet did not exist.
At that time, my belief was "It is my money, I can waste it as I please",,
So I started fertilizing the trees on about 2 acres, maybe 20 or so trees, I never bothered to count.

Anyways, over 30 plus years, these trees have shown a remarkable increase in health, and size.
The trees are oak, poplar, hickory,, as well as apple, cherry, etc..

Not knowing what to do, and not having the internet, I simply over-fertilized at the drip ring of these trees.
BUT, I had one oak, planted near a driveway, along with some shrubs that we planted at the drip ring of the tree.
That oak sucked 100% of the nutrients, and moisture near those shrubs. The shrubs just could not compete, and they did not survive.

After seeing that, I decided that the tree was capable of seeking out moisture, and nutrients.
I decided I would take advantage of that in my fertilizing technique.

I used a bulb planting auger, it is a mini post hole digger, that digs a 3 inch diameter hole, powered by an electric drill.
My philosophy was, that if the tree liked the fertilizer it would seek it out. If it did not like it, it would avoid it.

On a tree that was 12" in diameter, or larger, I would drill up to a dozen holes, and fill the holes with a balanced fertilizer (10-10-10)
As far as results, when I simply added fertilizer on top of the soil, around the tree, I would see stimulated grass, and weed growth.
When I added fertilizer to the 6 inch deep bulb planter holes, almost zero grass growth improvement was seen.
So, either the nutrients were simply washed away into the soil, or the tree got the nutrients.

During those years, the trees that were fertilized by the bulb auger technique seem to have grown double the diameter increase, compared to surrounding untreated trees. So, I feel my fertilizer addition has helped the trees to thrive.

(I think part of my reason for believing the drilling technique would help was that I was basically duplicating the "Jobe's Tree Fertilizer Spikes" that was popular when I started this test)

One of the things I have seen over the past couple years that reenforces my theory is an abandoned compost pile.
That pile, over 20 feet long, 15 feet wide, and 4 feet high has sat for over 10 years.
I went out last week to reclaim some of the compost, and found the entire pile was filled with tree roots along the top 10 inches of material.
Below the top 10 inches, there were no roots. Those roots knew where the most moisture, and nutrients were.
The tree roots were not waiting for the nutrients to wash down, the roots were climbing up into the top of the pile.

I have two 50 pound bags of 19-19-19 fertilizer. Soon, I will get out, and drill holes, and supplement the trees near my home, again.

What are your feelings on fertilizing mature trees?? I know it would be a "hard sell" to customers to show the benefits.
I am not doing this for a customer, I am doing this for my personal enjoyment.

Share your fertilizing info with us.

I would not bank on your findings so quickly. Here is why.
I worked for a tree transplanting company for over 30 years using a big John tree spade to move or relocate trees that were specifically planted for that task."Tree farms if you will" These trees were started in small 1 gallon containers and planted in rows to be moved with a tree spade at a later date when they matured to the proper size. All the trees started out the same size and of the same kind. Lets say live oaks for instance. We planted thousands of trees all at the same time in the same soil in the same fields. Some of the tree farms were irrigated and some were not. Some were fertilized and some were not. The one thing I noticed was they all grew at different rates and matured at different times even though they were all only about 20 feet apart and everything was the same for every tree in each field. The trees on the sides of the fields grew slower and shorter then the trees in the middle of each field. The trees on the sides didn't have to compete for sun light as much as the ones in the middle. It didn't matter where in the field the trees were they all grew at different rates. Some got bigger faster then others given everything was exactly the same for each tree.
The tree farms that were fertilized and watered had a much shallower root system and did not do as well after they were transplanted. They fell over much easier and went into shock and many died because they were dependent on the water and fertilizer they had received at the tree farm.
The tree farms that were not fertilized and watered had much deeper root systems and survived the transplant much better. They didn't blow over near as much nor did they die as much. They were forced to put down deeper roots to find water and nutrient's over the tree farms that had irrigation and fertilizer. But in every case the trees all grew at different rates no mater the conditions.
It was my observations that led me to believe it had more to do with the trees genetics over the conditions they were grown in.
These starter trees all were pruned every year to help them shape better and push there growth to make them taller and have a more pleasing shape.
I did this work over 30 years and in very different soils and locations and the results were always the same.
I do believe you can force a tree to grow differently if you apply different strategy's but it will come at a cost of how strong and durable the tree will be.
My findings tell me it is genetics that plays the most important role in the overall health and viability of each tree.
Over feeding and over watering will result in a much shallower root system and be prone to blow over and drought's then one that is left to fend for itself.
Because of how a tree spade works it is very easy to see the root structure and how deep the roots were.
I did find your observations interesting and makes me wonder what the root structure of the trees you treated and the ones you didn't are.

 

[sb47]

I would not bank on your findings so quickly. Here is why.
I worked for a tree transplanting company for over 30 years using a big John tree spade to move or relocate trees that were specifically planted for that task."Tree farms if you will" These trees were started in small 1 gallon containers and planted in rows to be moved with a tree spade at a later date when they matured to the proper size. All the trees started out the same size and of the same kind. Lets say live oaks for instance. We planted thousands of trees all at the same time in the same soil in the same fields. Some of the tree farms were irrigated and some were not. Some were fertilized and some were not. The one thing I noticed was they all grew at different rates and matured at different times even though they were all only about 20 feet apart and everything was the same for every tree in each field. The trees on the sides of the fields grew slower and shorter then the trees in the middle of each field. The trees on the sides didn't have to compete for sun light as much as the ones in the middle. It didn't matter where in the field the trees were they all grew at different rates. Some got bigger faster then others given everything was exactly the same for each tree.
The tree farms that were fertilized and watered had a much shallower root system and did not do as well after they were transplanted. They fell over much easier and went into shock and many died because they were dependent on the water and fertilizer they had received at the tree farm.
The tree farms that were not fertilized and watered had much deeper root systems and survived the transplant much better. They didn't blow over near as much nor did they die as much. They were forced to put down deeper roots to find water and nutrient's over the tree farms that had irrigation and fertilizer. But in every case the trees all grew at different rates no mater the conditions.
It was my observations that led me to believe it had more to do with the trees genetics over the conditions they were grown in.
These starter trees all were pruned every year to help them shape better and push there growth to make them taller and have a more pleasing shape.
I did this work over 30 years and in very different soils and locations and the results were always the same.
I do believe you can force a tree to grow differently if you apply different strategy's but it will come at a cost of how strong and durable the tree will be.
My findings tell me it is genetics that plays the most important role in the overall health and viability of each tree.
Over feeding and over watering will result in a much shallower root system and be prone to blow over and drought's then one that is left to fend for itself.
Because of how a tree spade works it is very easy to see the root structure and how deep the roots were.
I did find your observations interesting and makes me wonder what the root structure of the trees you treated and the ones you didn't are.

I would put money on the trees you did nothing to over the ones you treated as being stronger less prone to blow over and drought. They may be bigger but are they stronger? I bet money on the natural trees over the ones you treated.

 

[sb47]

I would put money on the trees you did nothing to over the ones you treated as being stronger less prone to blow over and drought. They may be bigger but are they stronger? I bet money on the natural trees over the ones you treated.

Have you ever observed a neighborhood after a storm and notice a tree that has blown over also took up half the yards soil and root system with it? Many yard trees grow with irrigation systems for the grass and are fertilized every year to keep the grass green and looking good. These trees generally have very shallow root systems and are prone to blow over and drought's over trees in yards that do not have irragation or fertilizer applied.

 

[sb47]

Have you ever observed a neighborhood after a storm and notice a tree that has blown over also took up half the yards soil and root system with it? Many yard trees grow with irrigation systems for the grass and are fertilized every year to keep the grass green and looking good. These trees generally have very shallow root systems and are prone to blow over and drought's over trees in yards that do not have irrigation or fertilizer applied.

I will add one more thing.
We would drive farther to a different tree farm that was not irrigated or fertilized to dig trees because we found we would have to replace the irrigated and fertilized tree much more often. Not only were they stronger trees but they were also not dependent on watering as often and we had a much better survival rate. It cost a lot of time and money to replace a tree that was under warranty.
To replace a warranted tree, I would have to go to the job site and lay out plywood to protect the grass and dig up the dead tree. Then drive to a tree farm and put the tree in the last hole where another tree was removed. Then I would have to cut down the dead tree so I could back up and get the next tree in line. Then drive back to the job site and put the new tree in the old hole and pick up all that plywood. Then I would have to send over a crew to sand the new tree in and mulch and water it. Every tree I had to replace took away from a new tree I could have planted and actually made money on.
Home builders and new home owners never took the time to properly take care of a newly transplanted tree so it became a big money loss if we tried to use irrigated trees. Sure they grew faster and the tree farmer could sell them faster but for us the cost of replacement of all those trees was a very high cost both in time and money.

 

[sb47]

I will add one more thing.
We would drive farther to a different tree farm that was not irrigated or fertilized to dig trees because we found we would have to replace the irrigated and fertilized tree much more often. Not only were they stronger trees but they were also not dependent on watering as often and we had a much better survival rate. It cost a lot of time and money to replace a tree that was under warranty.
To replace a warranted tree, I would have to go to the job site and lay out plywood to protect the grass and dig up the dead tree. Then drive to a tree farm and put the tree in the last hole where another tree was removed. Then I would have to cut down the dead tree so I could back up and get the next tree in line. Then drive back to the job site and put the new tree in the old hole and pick up all that plywood. Then I would have to send over a crew to sand the new tree in and mulch and water it. Every tree I had to replace took away from a new tree I could have planted and actually made money on.
Home builders and new home owners never took the time to properly take care of a newly transplanted tree so it became a big money loss if we tried to use irrigated trees. Sure they grew faster and the tree farmer could sell them faster but for us the cost of replacement of all those trees was a very high cost both in time and money.

It usually went like this. A new home owner would move in and have a brand new beautiful tree that was just planted in the yard. They also had brand new grass just laid so they would over water the yard to try and make the grass grow. Meanwhile the wife would want flowers planted around the newly transplanted tree so she would plant her flowers and add another 10/12'' of mulch on top of the thin layer of mulch that we applied when we planted the tree. Then they would crank up the irrigation system trying to keep everything alive. Not knowing or caring that they would be drowning the tree. You mix too much mulch with too much water and the tree would die before the warranty would run out. So we would have to go back and replace the tree. Let me tell you, you can't drive a 40K tree truck over new over watered grass without destroying the grass and leaving huge ruts in the yard. Even using plywood to drive over. Then of course we would stand a good chance of breaking the sidewalk and newly installed irrigation system. Don't even get me started on the home owner over fertilizing the grass and killing the tree.
Trust me, it happened all the time.

 

[muddstopper]

History of red oak. In or around 1974 we where cutting a tract of huge white pine timber. It was all on steep ground and we where using a dozer to skid the trees up the mountain. Got the dozer stuck off the side of a rock bluff and needed big wrecker to come and pull it out. The wrecker tied off to a small, 8-10inch red oak using a steel cable. Of course the cable practically ringed the tree stripping off some of the bark. In 1984, Dad bought property and built a house. The red oak was still alive and more or less was centered in the front lawn so dad left it to grow. In 1999 I bought the house. The redoak was in a state of decline, although it had grown to considerable size. It was hollow because of the damage from the cable back 25 years earlier. Big black ants where living in the tree and black ugly stuff leaked out thru the wound, many smaller dead branches where always breaking off and falling in the lawn. I started applying wood mulch around the base of the tree. The tree started recovering. Dead branches almost stopped appearing and the wound almost completely barked back over and the ants had disappeared. Diameter of tree had increased to about 32inches. It made a beautiful shade tree and the wife had several planters full of flower, azaleas, Rhododendrons in the raised bed we had made to hold the wood mulch, which I replenished every year. Sometime around 2015 or so, Lightning hit the tree and that pretty much did the tree in. After 2 or 3years of steady decline, paying to have dead limbs removed and doing what I could to save the tree, I finally had to cut the tree down. Made good firewood is about all I can say about that. The point of the story is replacing or trying to duplicate the forest floor with wood mulch allowed that damaged tree to live about 50 years longer than it had a right to live. Lighting did the tree in, it wasnt because of any fertilizer application, unless you count the wood mulch as fertilizer that kept the tree alive, or the damage that had been done 45 years earlier that finally killed the tree.

 

[sb47]

History of red oak. In or around 1974 we where cutting a tract of huge white pine timber. It was all on steep ground and we where using a dozer to skid the trees up the mountain. Got the dozer stuck off the side of a rock bluff and needed big wrecker to come and pull it out. The wrecker tied off to a small, 8-10inch red oak using a steel cable. Of course the cable practically ringed the tree stripping off some of the bark. In 1984, Dad bought property and built a house. The red oak was still alive and more or less was centered in the front lawn so dad left it to grow. In 1999 I bought the house. The redoak was in a state of decline, although it had grown to considerable size. It was hollow because of the damage from the cable back 25 years earlier. Big black ants where living in the tree and black ugly stuff leaked out thru the wound, many smaller dead branches where always breaking off and falling in the lawn. I started applying wood mulch around the base of the tree. The tree started recovering. Dead branches almost stopped appearing and the wound almost completely barked back over and the ants had disappeared. Diameter of tree had increased to about 32inches. It made a beautiful shade tree and the wife had several planters full of flower, azaleas, Rhododendrons in the raised bed we had made to hold the wood mulch, which I replenished every year. Sometime around 2015 or so, Lightning hit the tree and that pretty much did the tree in. After 2 or 3years of steady decline, paying to have dead limbs removed and doing what I could to save the tree, I finally had to cut the tree down. Made good firewood is about all I can say about that. The point of the story is replacing or trying to duplicate the forest floor with wood mulch allowed that damaged tree to live about 50 years longer than it had a right to live. Lighting did the tree in, it wasnt because of any fertilizer application, unless you count the wood mulch as fertilizer that kept the tree alive, or the damage that had been done 45 years earlier that finally killed the tree.

When I was planting tree farms for using to plant them on jobs with the tree spade some of the small trees would just not grow and just stayed the same size for years while the rest of the trees were growing great. We would take those small trees and strip all the leaves off and do a heavy pruning to them. We also would take a stick or shovel and give the little tree a good whopping and scaring the bark a good bit. That forced the tree to ether die or go into survival mode. They soon took off and accelerated there growth and quickly caught up to the other trees that were much bigger.
Growing up my dad planted an elm tree and it never seemed to grow and stayed the same size for years. One day someone had backed over the tree and did some heavy damage to it. That tree suddenly took off and started growing. It is still there some 50+ years later and is one of the biggest tree I have on the property.
I think it forces the tree into doing something to force it into survival mode to repair the damage and that starts it into staying that mode and it will soon start growing like it should have to begin with.
When we transplanted some trees to a job site they would just sit there and look sickly and not grow. We would do a heavy pruning job and strip all the leaves off. It wasn't long after that the tree would start growing as normal again. I am a firm beliver this works on a tree that just sits there and won't grow.

 

[Brufab]

When I started fertilizing mature trees, the internet did not exist.
At that time, my belief was "It is my money, I can waste it as I please",,
So I started fertilizing the trees on about 2 acres, maybe 20 or so trees, I never bothered to count.

Anyways, over 30 plus years, these trees have shown a remarkable increase in health, and size.
The trees are oak, poplar, hickory,, as well as apple, cherry, etc..

Not knowing what to do, and not having the internet, I simply over-fertilized at the drip ring of these trees.
BUT, I had one oak, planted near a driveway, along with some shrubs that we planted at the drip ring of the tree.
That oak sucked 100% of the nutrients, and moisture near those shrubs. The shrubs just could not compete, and they did not survive.

After seeing that, I decided that the tree was capable of seeking out moisture, and nutrients.
I decided I would take advantage of that in my fertilizing technique.

I used a bulb planting auger, it is a mini post hole digger, that digs a 3 inch diameter hole, powered by an electric drill.
My philosophy was, that if the tree liked the fertilizer it would seek it out. If it did not like it, it would avoid it.

On a tree that was 12" in diameter, or larger, I would drill up to a dozen holes, and fill the holes with a balanced fertilizer (10-10-10)
As far as results, when I simply added fertilizer on top of the soil, around the tree, I would see stimulated grass, and weed growth.
When I added fertilizer to the 6 inch deep bulb planter holes, almost zero grass growth improvement was seen.
So, either the nutrients were simply washed away into the soil, or the tree got the nutrients.

During those years, the trees that were fertilized by the bulb auger technique seem to have grown double the diameter increase, compared to surrounding untreated trees. So, I feel my fertilizer addition has helped the trees to thrive.

(I think part of my reason for believing the drilling technique would help was that I was basically duplicating the "Jobe's Tree Fertilizer Spikes" that was popular when I started this test)

One of the things I have seen over the past couple years that reenforces my theory is an abandoned compost pile.
That pile, over 20 feet long, 15 feet wide, and 4 feet high has sat for over 10 years.
I went out last week to reclaim some of the compost, and found the entire pile was filled with tree roots along the top 10 inches of material.
Below the top 10 inches, there were no roots. Those roots knew where the most moisture, and nutrients were.
The tree roots were not waiting for the nutrients to wash down, the roots were climbing up into the top of the pile.

I have two 50 pound bags of 19-19-19 fertilizer. Soon, I will get out, and drill holes, and supplement the trees near my home, again.

What are your feelings on fertilizing mature trees?? I know it would be a "hard sell" to customers to show the benefits.
I am not doing this for a customer, I am doing this for my personal enjoyment.

Share your fertilizing info with us.

I use a tree spade and use 19-19-19 mixed with a little pelletized lime and go around the drip line on about 20 native apple trees on some property we own. Seems to work good. Maybe 10-12oz in each hole as I use a plastic cup. I would say it takes a full year for the fertilizer to breakdown and absorbed by the tree. Non fruiting trees are now producing apples

 

[jolj]

Trees like humans never are to old for TLC.

 

[Lawless]

I fertilize my apples. They weren’t the greatest when we bought this place and I even lost 2.

All are doing well now. Mulch is very important. I think the fungus mycelium in the mulch is the actual hero.

 

[Seachaser]

I fertilize my pecan trees. It really improves production and avoids alternate bearing. They don’t like a high PH. OP, make sure you have a fertilizer that has zink and magnesium. We have trees that are 1, 50, and 90 years old. Irrigation helps, but can’t afford it........yet.

 

[jolj]

I fertilize my pecan trees. It really improves production and avoids alternate bearing. They don’t like a high PH. OP, make sure you have a fertilizer that has zink and magnesium. We have trees that are 1, 50, and 90 years old. Irrigation helps, but can’t afford it........yet.

Old wife tale, is rusty nails for iron, it does not work, need iron that tree can use.

 

[BusaDave]

One other thing to remember about mature trees is the root system. We have some live oaks near the house that are 150 years old. 30 years ago, when live oak decline was rampant here thought a couple of them, we infected-------turns out 150 yards away was the edge of the field where the herbicide MSMS was applied to a coastal field. It singed the leaves on the sides of the trees facing the field..... The root systems are Extensive so when adding nitrogen, the old adage to add fertilizer just around the drip line is not always applicable.

 

[All Pro Tree Service]

Have you ever done a soil test?

Have the trees shown signs of deficiency? Have neighboring trees in similar circumstances shown signs of deficiency?

My thoughts on fertilizing mature trees: what am I going to give them that they didn't have for the previous XY decades? Unless something changed in the soil or there are identified deficiencies, I think it is a waste of time and money. If they do need fertilized, I think it is a waste of time and money to do it without knowing what they need (soil and/or plant tissue test).

It's a simple yet valuable process that can give you insight into the health of your soil. By taking a sample of your soil and sending it to a lab for analysis, you can learn about the pH level, nutrient content, and other important factors that affect plant growth. This information can help you make informed decisions about what types of plants to grow and what amendments to add to your soil. A soil test is especially important if you're starting a new garden or experiencing problems with your current one. So if you haven't done a soil test yet, consider giving it a try to ensure the best possible growing conditions for your plants.

 

[pining_fir_yew]

My philosophy was, that if the tree liked the fertilizer it would seek it out. If it did not like it, it would avoid it.

Vertical Mulching like you describe is a method we used much more about 15 years ago. I never thought of that point being a benefit, but there's decent logic to it. We moved to using almost exclusively liquid injected fertilizers. Though, it was mostly due to the considerable difference in man hours between the two methods. Now Vertical Mulching is nearly exclusively only utilized in cases where compaction is a significant concern. I will likely use it much more once purchasing an air knife in the fall.

19-19-19 fertilizer

We also use 19-19-19 in a mix that we funnel into the auger holes : 75-85% mix of good soil, peat Moss and manure with more or less peat depending on how compacted the surrounding soil is and 25-15% a 19-19-19 mix with granulated sulfur (typically using Espona's soil acidifier).

If the tree is at risk of or has a history of hosting damaging levels of mites or aphids, I will avoid using anything with too much nitrogen. And I always opt for the slow release nitrogen..

What are your feelings on fertilizing mature trees??

I do fertilize mature landscape trees on a biannual or annual basis depending. I have some clients that have fertilized their highly valued trees for the last 25+ years. I always conduct a soil test at least every three years, or 6 years if on a biannual schedule. Deciding between biannual and annual fertilization typically comes down to my clients goals, the tree's health and history, as well as the soil test results.

I know these situations don't really apply to your case with established trees on what I'm assuming is a more a landscape with more of it's natural nutrient cycling systems intact, but I typically recommend regular fertilization for mature trees only in cases:

1. where there are specific nutrients that need to be regularly supplemented,
2. the tree was formerly declining but has since stabilized and ready to start "active" recovery
3. where resorption of nutrients that previous fall has interrupted due to defoliation
4. or if the tree is of average to good health and a highly valued specimen growing in a landscape that is extremely to moderately manicured.

Share your fertilizing info with us.

So, since you asked..

I know that many arborists are tempted to save a declining tree with a fertilization, and that's not necessarily the wrong instinct either. (it's almost always what a client will request right off the bat if their tree is declining)

I've moved away from trying to fertilize my way around many issues I see landscape trees typically experiencing. - except for cases of iron / manganese chlorosis. (tangent on that in purple below)

Old wife tale, is rusty nails for iron, it does not work, need iron that tree can use.​

​

I'd also add that if pH is too high, there is likely already plenty zinc and manganese present in the soil but it's locked up. Soil pH is the literal bane of my existence. In turf focused landscapes you'll get a triple whammy for high pH: excessive lime applications, over irrigation, and all leaf and needle "litter" is obsessively cleaned up. I regularly see pines that look miserable in a pH that's like 7.8-8.5. Absolutely insane.​

​

What's worse is that pH is so difficult to lower. Keeping it low is a constant chore. Just another reminder that right tree right place are words to live by.​

Examples of situations where we would have been tempted to try fertilizing around compacted soils, repeated summers of drought conditions (typically juvenile trees that were lovingly irrigated hose drip irrigated for the first 5-7 years then forgotten about for the years proceeding), herbicide and salt damage, over-irrigation, and absolutely brutal root damage from construction. The extra nutrients in these cases are likely not going to significantly improve the tree's situation.

In cases of root damage especially, tree decline above ground usually becomes evident to the homeowner around 3 - 4 years too late. I've become a huge proponent of using biostimulants and plant hormone treatments to stimulate root recovery, drought resistance, enhanced chlorophyll action, etc.

I've paclobutrazol or cytokinin treatments, with beneficial bacteria along side organic soil boosters in cases where I thought recovery was unlikely, but possible. And so far, I've been pleasantly surprised to see slow, but improvement over 3 years in many of the trees I've worked on. (I see good success with the red oaks, maple, elm, plane trees but have a very difficult time nursing eastern white pine back.) Often I'll tell clients that I couldn't be happier to see no further decline or improvement one year after starting treatment. That seems to set expectations appropriately

I'm still iffy on introducing mycorrhizae. but there is a lot of work going into developing better bio-stimulants, so hopefully in the coming years I'll feel more confident that the little guys aren't just dying as soon as I introduce them.

Anyways long story short: trees rule, turf drools, test ur soils, read ur labels.

 

[Seachaser]

You really need a healthy base for the entire root system. Then every time you mow, it enriches the soil.