Fruit Tree Nutrient Deficiencies

Learn how to look at fruit tree leaves and identify common nutrient deficiencies (ie a lack of nitrogen, magnesium or boron) with Eric Hanson, Professor Emeritus of Horticulture Michigan State University.

The host of the Orchard People radio show and podcast is Susan Poizner of the fruit tree care education website www.orchardpeople.com.  

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• (00:00) - Introduction
• (00:45) - Identifying Nutritional Deficiencies in Trees
• (01:21) - Guest Introduction: Eric Hansen
• (02:20) - Soil Testing and Its Limitations
• (06:31) - Tissue Testing for Nutrient Deficiencies
• (09:09) - Visual Diagnosis of Nutrient Deficiencies
• (10:55) - Nitrogen Deficiency in Fruit Trees
• (17:05) - Potassium Deficiency Symptoms
• (20:37) - Magnesium Deficiency in Orchards
• (23:59) - Understanding Manganese Deficiency
• (29:16) - Commercial Break and Sponsor Messages
• (32:58) - Introduction and Contact Information
• (33:31) - Interview with Eric Hansen: Nutritional Deficiencies in Fruit Trees
• (33:56) - Boron Deficiency in Fruit Trees
• (44:05) - Zinc Deficiency in Fruit Trees
• (50:35) - Iron Deficiency in Fruit Trees
• (56:26) - Holistic Approaches to Tree Nutrition
• (01:00:05) - Conclusion and Additional Resources

Creators & Guests

Host

Susan Poizner

Author, fruit tree educator, and Creator of the award-winning fruit tree care education website OrchardPeople.com.

What is Orchard People?

Learn how to grow and care for fruit trees with fruit tree care educator Susan Poizner of OrchardPeople.com. Discover how to create permaculture plantings, food forests, and forest gardens in both urban and rural settings. Meet experts on all aspects of comprehensive fruit tree care, including pruning, pest and disease prevention, fruit tree grafting and budding, and soil management.

Show host Susan Poizner, creator of the fruit tree education website OrchardPeople.com, is an award-winning author of three fruit tree care books and an ISA Certified Arborist. This podcast is the winner of the 2021 GardenComm Silver Award of Achievement for Broadcast Media: Radio Program Overall. Learn more and access archived episodes at https://podcast.orchardpeople.com/.

Learn more about Susan's books and courses at https://learn.orchardpeople.com/books.

Hey, welcome, everybody. Recently, I had the opportunity to visit a beautiful garden in Connecticut. Everything was thriving in this garden. There were flowers and herbs and vegetables. The peach trees were so healthy. Everything looked great, except for just one tree, and it's a very old apple tree. So, I looked at the apple tree and I saw maybe some possible symptoms of disease, but it didn't really look like anything I was able to identify right away.
And I thought to myself, wouldn't it be great if I could look at tree leaves and know exactly what's going on, especially if there is a nutritional deficiency?
Well, the truth is there are some nutritional deficiencies that you can see when you're looking at tree leaves. And that is what we are going to talk about on the show today.
So in this pre recorded special episode, you'll be able to listen to the show. If you're listening on reality radio 101, or you can head on over to the Orchard People YouTube channel, and you're going to get to see lots of visuals of all the diseases or not diseases of all the nutritional deficiencies that we are discussing in the show to get today.
My guest today is Eric Hansen, and he is professor emeritus of horticulture at Michigan state university. So Eric, tell me a little bit about your job. What is it that you did in terms of identifying nutritional deficiencies in fruit trees?
Yeah, most of my job, was working for the extension service. so I spent quite a bit of time, helping extension educators, to identify, problems.
We, we did some research trials on, various nutritional problems that growers had encountered in orchards and elsewhere and, in Michigan. And then I, taught a couple of, classes, one on, mineral nutrition of plants in general. So I've had, been working in nutrition for quite a few years at different levels.
Now when you're working with commercial growers, I'm assuming a lot of the work that you do is by testing the soil, isn't, is that the main way you find out what nutritional deficiencies there are in the, trees?
soil testing is valuable, but it has limitations and in orchards and other perennial crops.
So it's important to test the soil to know what your pH is, to know what the general nutrient levels are in the soil and a soil test will do that for you, but it doesn't tell you everything. So one of the limitations, for example, is we don't have a good. Reliable soil test for available nitrogen. Well, nitrogen management is a real key component of effective fertilization program for, orchards.
So that's a limitation. And then a bigger general limitation, I think, is that when we collect tissues, from the tree, and we, compare those to soil nutrient levels, they often don't correlate very well, so you might find an orchard with, excessive levels of potassium in the, tree, but very low potassium levels in the, soil test.
So it's, I guess My guidance would be don't, don't put too much credence into what the soil test is telling you. It's a general measure of nutrient levels. I think the most important thing is it tells you where your pH stands.
When I'm working with students, I do want them to take a soil test, one, in the beginning, just to see where their soil stands, what is in the soil, but I love what you said, how you can have nutrients in the soil that don't get into the tree, or you can have nutrients in the tree that aren't in the soil.
So, what would cause those, that mismatch?
That's a great question. I think the primary, cause to me is, when you're trying to monitor that nutrition of a, big nutri big, perennial plant like, apple tree, that's been there for, for a decade or two or three, it has a root system that's, very extensive.
we sample the soil, in the top, eight inches or so of soil. it might be that the soil, below that is, has an abundant level of, potassium or other, elements. So your soil test might come back saying, oh, you're deficient. But the tree is still extracting enough of that nutrient from depths that you can't sample from.
Amazing. So that would explain why the tree might have lots of a nutrient that you can't find in the soil. What if you have lots of nutrients in the soil that somehow doesn't get into the tree? What could be the problem there?
Yeah, I think sometimes it falls back on the same issue that you're trying to sample the soil where most of the roots are feeding from.
So during dry conditions on a particular summer, for example, you might find that the feeder roots in the top six or eight inches where you're sampling are not very functional. That, the trees deriving its, water and nutrients from depths below that, so that might be an explanation for the, poor correlation between what gets in the tree versus what you measure in the soil.
Okay. So here we are, we've got this soil test with its limitations, and you are working for instance with commercial growers and you need to help them.
Is the next step then to take a tissue test, that's a plant tissue test, and what would that look like?
Yeah, I think that's the most reliable indicator of the nutrient status of a perennial, plants like an apple tree.
and the standard procedure there is to, take leaves, leaves only, and, typically from the middle of the current season's, shoot. So the trees are growing a shoot, each year. And you would take a mature, leaf from the middle of the shoot, and that would typically be taken in July here in, in Michigan, or just generally in the middle of the growing season.
you would want to sample, 50 to 100 leaves. And if you only have 10 trees, then you, might sample 5 to 10 leaves per tree. If you have a 5 acre orchard, you want to take leaves from as many different trees in, in the orchard, so that your composite sample of leaves. is representative of the whole orchard.
And then you can send those into reputable labs. If you don't know of a lab to use, you might contact your extension educators in your area. They usually know where to go with that sample.
Oh, fantastic. Okay. So with the commercial growers, you would do a plant tissue test. Now I'm assuming they are available for home growers.
They may be a little expensive, I'm guessing. Do you know much about that?
Yeah, I haven't looked at prices recently, but you're right that they are expensive. So and that's why a lot of growers even Commercial growers, probably don't use that, service as much as they should, in my, opinion, but it might be, 25 to 35 to have all the nutrients analyzed in one leaf sample.
So that's a turnoff for some people, certainly would be for some. backyard orchardists who, really are just interested in growing their two trees. but, I think it provides the best, most accurate, reliable information about the nutrient status of the plant.
Fabulous. Okay, so for commercial growers, even for home growers, that is an option.
And then there are your eyes and observe observation and looking at the leaves. To what extent is that a useful tool when it comes to diagnosing or deciding whether a fruit tree has a nutritional deficiency?
Yeah, it's, partly science and partly art to me. it takes a lot of, years of experience looking at different problems in, orchards and some, commercial growers that have been at it for a long time are at.
excellent experts at diagnosing what they see in the field. But the problem with it is there are a lot of, other maladies in fruit trees that look similar to the symptoms that you'd see as a result of, nutrient deficiencies. So it's fairly easy to misdiagnose problems based on what you simply what on in the leaves on a tree.
It's not to say that it's not important to understand. And there are some great online resources for, with, collections of images of different nutrient deficiency symptoms on trees. So you can, it can be helpful.
Okay, well, I think we should dive right in because let's discuss it nutrient by nutrient.
And for those people who are watching this on YouTube, you will be able to see some of the pictures. If you're listening to an audio version of the show, we will describe what we're looking at. So let's have a look here.
Okay, so let's start with nitrogen deficiency. Nitrogen is important for fruit trees because why is this such an important nutrient for fruit trees?
In orchards, the single most commonly limiting nutrient is, nitrogen. so managing nitrogen levels is, is really critical, to, because it's quite often deficient. It's also the case that if you're over fertilizing fruit trees that you can cause issues too. So if you over fertilize apple trees, for example, you'll create an excessive vegetative growth that makes pruning a longer job.
It also reduces potentially the quality of the fruit that you get from the fruit trees. From the tree. So managing trees with the right amount of nitrogen is pretty important
for my personal experience. So we planted our fruit trees in a community orchard in our local park where the soil is was and is not very good.
And I remember looking at those trees and thinking they were fine, where the park supervisor at the time who loved growing fruit trees. He looked at our trees and he said, Oh boy, they're Those trees need more nitrogen because he saw the time it was in the summer. We had planted these trees and there was hardly any growth.
You couldn't see any new growth. They looked like the exact same tree that he had picked up from the nursery or from the garden center and we planted. So, for me to understand nitrogen deficiency was to understand that if you don't have a lot of new growth on your tree, you're Possibly have nitrogen deficiency.
In fact, it's pretty likely. Is that correct?
Yeah, that's certainly one measure of, nitrogen status. So the tree's growing well. And that being said, if you're going through a drought, situation or, that they could be growing poorly on a given year because of water, stress too, but lack of nitrogen reduces growth.
And there was an old, standard, rule of thumb when I first started working, that, for apples or pears, your goal might be to grow eight to 12 inch, shoots during a year. And for, stone fruit, like, peaches, it might be, one to two foot long, shoots. So if you're not getting that, then it's potentially you're not getting enough nitrogen into the tree.
So for me and for us in our group, we would actually go out with measuring tape and we'd, see what, whether it's at the end of the year to see if we had that one foot of growth or two feet. so that's a great tool to see, okay, am I getting enough growth or perhaps am I lacking in nitrogen?
But you have also given me some pictures of what nitrogen deficiency can look like and how it might exhibit itself in the leaves. So describe to me what we're seeing here.
Yeah, these are just some pictures that I've collected over, over the years of apples and, peaches, that are lacking nitrogen.
And the thing to, a couple of things to remember. First, the color of the leaves, is, washed out. So you tend to get, a lighter green color instead of a healthy dark green color in the leaves. The leaf size might be reduced. We mentioned that the shoot growth is usually reduced. And then another really interesting aspect of nitrogen is that it's mobile in plants.
So, fruit trees can re mobilize nitrogen from the old leaves. and move it to the actively growing shoot tip, where it's most needed. So a characteristic of nitrogen, lack of nitrogen symptoms is that the most severe symptoms, the porous color are usually in the leaves towards the base of the shoot.
And you can, see that on the, peach, picture. here, but what's happening is the tree is able to take the nitrogen out of the older leaves that are not as important to the tree and, move that to the, younger leaves towards the shoot tip. So if you see that kind of pattern, that's another indication that the nitrogen levels are low.
Oh my gosh, that is so touching. It's if a family, is living in a country where there's not enough food and the parents hold back and they're like, okay, I'll go hungry. Let my children eat. So isn't that so touching that the fruit tree will bring, the nutrients to the, little leaves growing at the tip because that's their future, I guess that's, is that why those little leaves are so important?
The younger leaves?
Yeah, it's pretty good analogy. I don't know the, how much, thought trees give to it, but, yeah, certainly value the younger leaves over the, older, older, mature leaves.
Well, I should be a tree psychologist then. . Okay, so, so we are looking for, with nitrogen deficiency, the leaves may not be very dark green.
they also may be lighter in the older part of the branch, and moving the darker green to the end. So, that is a sign. Those are perhaps signs of nitrogen deficiency. Let's move on and let's talk about another important nutrient here.
Let's talk about potassium deficiency and what that might look like in the leaves of a fruit tree.
tell us what role potassium plays in, why is potassium important with fruit tree growth and production?
It has a number of different functions in trees on a physiological level. But a lot of it is related to water management in, the trees. So when one function, for example, is to allow the trees to.
Open and close these microscopic pores on the trees to regulate water loss, but a number of other functions is as well. And quite often that brings up an important point is quite often, in science, we talk about the function of nutrients and plants. But the symptoms that you see in trees or, any plants that are deficient, very often don't relate to what the nutrient does physiologically in, in the, tissues.
but in, in the case of potassium, the classic symptoms of, deficiency Are, leaf curling and, burning or necrosis along the margins of the leaves. So a couple of those pictures, show in, tart cherries on the upper left, the curling that can occur and, you might expect maybe that looks like, water stress and it's very similar to water stress.
But, that's caused by inadequate, potassium and then the, burning along the margins of the leaves on the, lower right, is the other classic symptom of potassium, deficiency.
Well that's very helpful because, burning along the margins, so if we're looking at the leaf, we can see, sorry, death or like of the tissue or just like brownish The sort of the outside of the leaf margins is the outside of the leaf.
That's a really cool thing to recognize and be able to recognize, to show you about potassium deficiency. Something you've mentioned a couple of times is the role of water. Why drought makes our problems worse. And one thing that I've said to people, it's fruit trees, they don't have teeth, so they can't chew their nutrients, which means that they have to only bring in nutrients in liquid form.
So if a tree is dehydrated and can't access, Water in the soil, because there is none, then it's also starving and it's going to have nutritional deficiencies. So does that relate here with potassium or even nitrogen?
Yeah, I think it can relate to any of the uptake of any of the nutrients that you're absolutely right.
That they're all absorbed and in solution. so the tree is pulling water. into the roots. And as it does that, it's supplying, what, dissolved, elements are in the water to the tree. So if, the tree is shutting down because of water stress, the supply of nutrients also is diminished.
Got it.
Okay, so let's continue on, to see our next nutrient, and that's magnesium. All right, so why is magnesium important for our fruit trees, our apple trees, cherries, apricots, peaches? What does magnesium do?
Well, again, multiple functions, but, one of them is, a component of a chlorophyll molecule. so that's, just one of the physiological, functions.
Magnesium is quite often, deficient in orchards in Michigan. And I think in a lot of areas of, Midwest, us and, Canada. it's not as commonly deficient as nitrogen, for example. And certainly, potassium, but we do see deficiencies of it, and it's a more difficult one to diagnose.
So, you can see in one of these, pictures, chlorosis and, eventually necrosis. The burning of the tissues along the margins of the leaves and the difference between that and potassium deficiency is the burning along the margins due to potassium deficiency tends to be fairly uniform. So it's a band around the outside of the leaf.
And in this one picture on the upper right. you can see that the necrosis or the burning extends in between the main veins of the leaf. So it, it results in a kind of a Christmas tree shaped center of the leaf that's, that retains the green color. With the burning along the margin, so it's a little different than potassium deficiency and then potassium.
I had neglected to mention is also a very mobile element in plants. So that like nitrogen, you'd likely to see the symptoms developed first on the older leaves. on a, shoot and then progress up to the younger leaves. In the case of magnesium, it tends to be fairly mobile as well. So you'll usually see the more severe symptoms further down on the shoots on the older leaves.
And, it's not to say that it can't affect, younger leaves as well, but that's just another diagnostic, characteristic of magnesium deficiency.
Oh, it's so exciting because these are all wonderful concrete hints. So, if we're looking to see, Necrosis, which is the death or the burning look of the leaves.
So, with magnesium, it's not just around the edges of the leaf, it starts to move in towards that central line of the leaf and, between the veins. Of the leaf. So that's great. And also we'd be looking at older leaves. they might be more likely to get it. Wonderful. Let's do one more and then we'll just have a little respite for our commercial break.
But let's just talk about manganese next. Tell me a little bit about manganese. That's not one that people really think as much about. Usually you go to get your NPK fertilizers. with just the, big nutrients. So why is manganese important for fruit trees?
Yeah, we've talked to this point about the, what we call the macro nutrients.
So nitrogen, potassium, phosphorus, magnesium. so manganese is, referred to as a micronutrient. So it's not that it's less important to the plant. The plant can't survive without it. But, the quantities that are needed by the tree are much, much lower. So that's why it's called a micronutrient. And, manganese is an interesting one and also often confused with, deficiencies of other, elements.
iron deficiency will cause similar symptoms. You can see from these pictures that the leaves retain a green main vein and major veins in the leaves while the rest of the leaf is turning chlorotic. So it it's similar in some respects to magnesium deficiency too. The difference is, or one difference to look at is that The manganese is not very mobile in plants, so if you look at the shoot on the lower left, those leaves are affected right out to the tip.
So the oldest leaves are affected as well as the youngest leaves. So that's a clue that you're probably dealing with a nutrient that's not very mobile in the plant.
We're turning into private detectives here, detectives of nutrient deficiencies. Okay, so manganese, it's, you can see that it's different.
I'm not seeing a lot of dead tissue, like we've seen in the previous ones. So the leaves, are green, but they're different colors of green. The, chlorosis makes part of the green look, quite yellow. So, like you say, you've got our, we've got our veins that are still dark green down the middle of the leaf.
And then the sort of secondary veins at the side are still dark green, but the rest of the leaf is looking sort of a lighter green and not too healthy. So that's manganese. Yeah.
That's a great description. I wanted to mention a couple other things about manganese that are, interesting too, is if you're using herbicides, pre emergent herbicides that are applied to the soil, some of those, if you're applying too much and they're stressing the tree, will develop symptoms that are real similar to, this too.
So you'll see this, interveinal, chlorosis that's often hard to separate from a nutrient deficiency. And then the last thing I wanted to say about manganese is there's a picture of, scaly looking apple bark on a, branch. And that's, a picture of internal bark necrosis.
And, it's caused by manganese, but not inadequate levels. It's caused by, excessive levels. So it seems for some reason to concentrate in the, cambium tissue just under the bark and cause damage there if the tree is getting too much, manganese. So this is the first time we talked about, toxicity, due to, a nutrient in addition to deficiency symptoms.
I'm so glad you brought that up because, what, there, there is this tendency of over nurturing your tree. Well, just in case it has a deficiency, let me throw some fertilizer at it. Let me get some, oh, I hate them. The, fertilizer fruit tree fertilizer spray. Spikes that people get online, and it's giving your tree nutrients that it may not need.
And you get so many bad reactions. So it is such a delicate thing, where you want to get just the right amount of these nutrients and not too much. that's why it's so important to do your homework and to feed your trees really carefully. I would think. Do you agree?
Yeah. More. More. It's not always.
better. And, it's also true that, try to understand the most common nutrient problems that you're, that other people have experienced in your area. It, varies from region to region, somewhat, but if you understand that, three quarters of the problems, nutrient related in orchards in your area.
are due to nitrogen, and or potassium, then it gives you a feel for whether you should even be concerned about deficiencies of some of these other elements.
So Eric, I want to go into more detail about some more nutritional deficiencies and what we would see on the leaves of our trees, but I would like to first hear a few words from our sponsors.
Are you okay holding on the line for a couple of minutes?
That's wonderful. Sure. Sure.
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In the show today, we've been talking to Eric Hansen. He is Professor Emeritus of Horticulture from Michigan State University.
And we have been talking about nutritional deficiencies in fruit trees and how to recognize them. So in the first part of the show, we talked about nitrogen. We talked about manganese. We talked about some other nutrients.
Okay, so we're looking at some pictures here of boron deficiency. Tell me a little bit of what boron is and how important that is for fruit trees.
Yeah, again, it's another micronutrient. So the trees don't need much of it, but they won't survive with, without it. And it's a peculiar thing because it was over a hundred years ago that scientists, learned that, plants have a boron requirement. It's an essential element, but it took until about 15 years ago before an actual function of boron was recognized.
So we, now know that it's, forms kind of a cement holding together parts of cell walls in, that surround each, cell in, in plants. But it was pretty fascinating that, people understood that plants need it, but it was so long before scientists could figure out what the purpose was for it.
What, it did.
So is boron important in all the tissue, like in the branches and the leaves and in the fruit, or is there a certain part of the tree that it plays a more important role?
Yeah, every, every tissue, every cell type in plants have a boron requirement. It's a matter of what in a deficient plant, has more to do, with the, mobility of boron in, in plants.
So this is one that, except for, some, species is, fairly immobile in, in plants. So, there's a picture shown of a shoot that's an old picture. It was taken in the Hood River Valley of Oregon years and years ago. But, it's called a dieback of shoot tips. So the shoots will grow seemingly normally early in the season.
And then they'll get to a point where they simply run out of boron. And the tip of the shoot will die back. And So shoot, tip die back.
And is that just in apple trees or will that be in peaches and cherries and everything and all the other trees?
it can occur in, in all trees. It, part of the, part of the reason that this occurs is that, trees have difficulty moving boron from the older tissues to supply the actively growing, shoot tips.
some species, have, provide more mobility of boron, in the tissues than others.
That's so interesting. So you've been talking about mobility. I love this idea that a fruit tree takes in nutrients and some of the nutrients are happy moving around. They'll go everywhere. They just ride the sort of water slide inside the plant.
They can almost be drawn up into different branches. They can move to the old leaves and the new leaves. And some nutrients are just like, no. I'm staying where I am. I am not mobile. I'm not going anywhere. And yet you're saying that in this case of boron, it's not the nutrients. That's mobile, but it's like the cultivar in some cultivars that can move around and in some it can't
well, it's more species related and it has to do, some species, transport, sugars and some species transport sugar alcohols.
This is probably more detail than anybody cares to know. But, the boron actually, attaches to sugar alcohols, and so it can move in those species that use those as carbon transport molecules.
So give me an example of a species where boron is moving around no problem.
sour cherry, for example.
And, sour cherry, we, did some work, years ago where we used a, label form of boron and we'd apply it to leaves. And Within a few hours, you could document the movement of that boron out of the leaves. And what that means is boron is transported, it's called primary transport. So it's transported with the water that the leaves are transpiring or losing to the atmosphere, and that deposits the boron in the leaves.
But then there's another transport system that can move, boron out of that leaf and into other parts of the, tree. And in the case of cherries, it's, has a mechanism to, to do that.
So sour cherries, boron moves around no problem. Are there other species, I don't know, apple or pear or apricot where boron is present?
It's a little notoriously slow,
the, a good example would be, nut trees, for example, they, are, don't have that, sugar transport mechanism, or the, sugar alcohol transport mechanism, So they, can't move boron, and as a result, then you're likely to see the, actively growing shoot tips to grow themselves into a deficiency as the, season goes on.
huh. Okay. So boron, you might see die back of shoot tips. I see also that there's this issue of bark necrosis. So parts of the bark might die as a result of that boron deficiency.
Yeah. And that's something I've never run into in, in the Midwest, but in the Pacific Northwest, I know that, that has occurred.
So it similar to, bark necrosis caused by manganese toxicity, but it's caused by actually a lack of boron, in those tissues.
Interesting. Okay. Let's go on to another nutrient. Oops. I just went too quickly. Oh, hang on. So we were talking about boron deficiency in the shoots, but I see that boron deficiency may also affect the fruits.
What would that look like?
Yeah, boron has a lot of peculiar effects on, in fruit trees. And one of them is disorders of the fruit. So the fruit, can develop a corking. So there are some pictures of apple fruit that are severely affected. They have, necrotic, areas in the middle of the flesh of the fruit, and you can tell that those are there just by looking at the outside of the fruit.
And then also corking. So there are a couple of pictures of, splitting and cracking in a pear fruit and cherry fruit. And this. Relates to transport of boron in the plant probably, but also how actively or quickly growing those tissues are so young apple fruit is growing very, fast and it may be that it's just growing into a deficiency because the supply of boron can't keep up with the growth rate of that, organ.
Go ahead. Sorry.
I was going to say the other peculiar things is boron is very important in the fruit set process. So pollination and fertilization of flowers requires boron. So there's a picture of grape. berries, that should be a beautiful large cluster and it's just a small cluster with some little tiny, berries that probably contain one seed if, no seeds.
So pollination is an important, component. And then there's also a picture, on the upper right, and that's a symptom called blossom blasting. And it's, again, not seen in the Midwest that I know of, but, was common in the Pacific Northwest. And this is where the flowers develop, seemingly normal, but they get to a certain stage and then they just turn, turn brown and drop off.
So they're, they blast. And that was due to inadequate boron uptake in the fall. So what, people have found is that For a healthy flower, there has to be enough boron reserves in the, spur and in the young twig tissue to supply the development of the flower in first thing in the spring.
So with this boron deficiency, I'm getting, we got lumpy fruit, lumpy looking fruit.
No, it's easy to confuse that with certain pest issues as well, or disease issues, but you got lumpy fruit. You cut the fruit open, for instance, the apples, it's bad. Browning inside. I've, I see here, cherries that are deformed. I see fruit that's too small. So a little bit of boron is necessary and without it, you can have big problems.
So very interesting. Let's look now, we've got just a couple more to talk about.
I want to talk about zinc. why is zinc important and what will it look like if we have a zinc deficiency?
Yeah. Zinc is another micronutrient. one of the functions is in the pathway for development or production of, auxin in implants and auxins, a growth regulator.
And this is, I think one of the few nutrients where the symptoms that develop have something to do with the function of the nutrient in the plant on a physiological level. So one of the symptoms is, shown in the picture on the lower right is, peach shoots that have a full complement of leaves, but they haven't extended.
So there's a tuft of leaves at the tip of the and that's called a rosette. And it's fairly, easy to, identify when you, see it, but opsin, causes elongation of, shoots. It is an important regulator in, that way. So you can make the case, well, maybe here's a nutrient that's required for production of a hormone.
And if that hormone's not produced, then you see a symptom of rosetting in the, in the young shoots. Okay.
Wow. Yeah. So when you're looking at this, I'm looking at a bunch of, branches, mostly from peach trees here. I can't really tell, but they look pretty bald. The leaves are too small.
They just look very sad. They're not extending properly. Can this, if this is in peach trees, does, would you see this as well in apple trees?
Yeah, I think these pictures, again, they're quite old, are in apple. And it, they show a second symptom of zinc deficiency, which is, little leaf and blind wood. So, it's a peculiar situation where if the trees are, short of, zinc, the, leaves that develop on last year's, wood.
So that's lower down on the, branches. tend to develop poorly, so they might be very small, and in some cases those buds may not develop at all, so that you have blind wood, or leafless wood, below the current season's growth on the tip of the shoots. So you can almost imagine if, once you get familiar with that, if you were driving down your orchard row, you'd probably be able to recognize that, because it's standing out right on the, end of the, end of the shoots.
Well, I've seen something like that before in our orchard. So we have mostly, trees that are disease resistant. And because they're easier to grow, and I, like encouraging people to grow those trees. But there's one tree that is not resistant, and it's struggled over the years with a nasty fruit tree disease called fire blight.
And right now it doesn't seem to have fire blight, but if you look up into the canopy where all the other trees, the apple trees, are leafy and they filled in, we pruned them carefully so there's nice open air circulation. But this poor little tree, the leaves are so small, there is definitely you know, what do you call it?
Blind wood, yeah, where there's not really, there's some parts of the branch that there's not really many leaves. It's trying so hard. So perhaps it could be a zinc issue. Maybe it's something else. This poor tree is struggling. one thing that comes to mind when we're talking about this is as people listen to this episode, they'll be like, Oh, okay, I have to get a bag of boron for my tree and I have to get some zinc for my tree.
And I think. My perspective is as a person who is a small scale grower, and probably even, commercial growers need to think about this too, you want to have a tree that is generally healthy rather than, putting this ingredient and that ingredient, the more you can invest in the general health of your fruit tree and feeding it annually with compost or, not in natural ways, then hopefully the balance will come on its own.
Is that possible? Is that true?
Yeah, I think that's a great, great point. in, a lot of cases, we can avoid, deficiency problems. By providing a holistic, approach to orchard, nutrition. So, compost, for example, that are, produced from, plant material, contain all the essential elements that, the tree needs.
It might not contain everything that the tree needs, but it's a great starting point is to build a healthy, functional soil to begin with. And you're much less likely to. run into deficiencies of, particular elements.
Absolutely. Our, favorite thing in our orchard, we're not really allowed to have a vegetable compost bin or whatever, but we do collect the leaves at the end of the year from all over the park.
We pile them up. And as we weed in the spring, any weeds that don't have weed seeds that are invasive, we pop on that same pile and the pile just disappears over time. But that kind of thing is a living compost. There's going to be, like wonderful, healthy, friendly bacteria in there, so for people to start to think, I also have at learn.
orchardpeople. com. One of my courses is specifically on soil and how to improve your soil to have healthier fruit trees. So if people are interested, they can have a look at learn. orchardpeople. com and check out my soil course, because there are so many natural ways to help our trees without getting bags of this and bags of that.
And it's also healthier for the environment. So, okay. We have one more. Let's see. Let's see, let's talk about this.
I think we've come up close to the end of the show, but I want to talk about iron deficiency because this is one, that I've seen a lot of examples of in various plants over the years. So tell me why iron is important.
Yeah. So iron, regulates a number of different physiological processes in, plants. In the plant, it's a very immobile element, and it's a great example of that are these pictures of deficiency. So you can see, in each picture that the most severely chlorotic leaves are on the very tips of the, the shoots.
So it's a case where the plant might want to maintain the health of those youngest, shoot tips, but there's no way to move iron from the older tissue to maintain the health of the younger, shoots.
when you say chlorotic, is chlorotic essentially yellow? It means that the green tissue is not looking green.
It's yellow. Is that what chlorosis is?
Yeah. Chlorosis is, loss of the normal, leaf color. Whereas chlorosis is what people, term people use to talk about dead tissue. So, it's gone past, chlorotic. It's, necrotic.
Oh, chlorosis, chlorotic versus necrotic. Correct. Necrosis. With an N, that's dead tissue, but chlorosis is living tissue, not looking so good, turning yellow, and I can see in these pictures, you do have lots of photos showing that especially the young leaves are turning yellow in various trees, and you're saying that's because the iron is one of those stubborn nutrients that will not move around.
So perhaps the older leaves are part of the branch that did have iron at that time. So they're, they, the green, they're green, they're fine, but somehow the iron is not going into the newer leaves.
that's a great way to describe it. Yeah.
But I'm just curious because If iron isn't a mobile nutrient, it has to come into the tree through the roots anyways, unless you're doing, some sort of, foliar spray on the leaves.
So it must somehow be able to get to the new growth.
Yeah, there's a certain supply that's happening all the time through the transpiration stream so that all those leaves are, losing water. They're pulling it up through the roots and iron is to some degree in that water early in the season. I think there's more water generally available, in a general sense.
So there's more, Iron that's supplied to the younger leaves early in the season. Then when you get into mid summer, it might be that the water supply is somewhat diminished, and the iron supply to the younger leaves is diminished as, a result. So they, catch the problem, quicker as a result.
And the other thing is, I wanted to mention too, we talked about the importance of pH. So when I see symptoms of iron deficiency. It tells me just about immediately that the pH of that soil is too high. So a high pH soil, binds up iron, so there's less available for the plant to take up. So when you see iron deficiency symptoms, it usually indicates that the pH is way too high.
So the bottom picture here was from a colleague. MSU, Frank Dennis, who, was visiting Mexico and, they, that's a arid, environment and most arid environments, have soils that tend to be more, alkaline, high pH. And that's what's causing the, iron deficiency in that, small tree.
Yeah. pH is very interesting because, it depending on the pH of your soil, you can have, from what I understand, you can have nutrients in it. It's in the soil, but they can't get into the tree in certain pH. Is that, how does that work exactly?
In most cases, it's, a simple chemical reaction.
So at a certain pH, element may be, soluble. At a different pH, that element, precipitates out of solution. It becomes insoluble, so it's not, no longer available to the plant roots.
So that is so simple.
Yeah. It's usually just a chemical, situation.
And that brings us back to what we discussed earlier, this whole idea that fruit trees don't have teeth.
They have to suck in the nutrients in a liquid form. And if the nutrient is not soluble, in the pH of your soil, well then tough luck fruit tree.
Is there any other thoughts or suggestions that you can share with us for home growers that really want to look after their trees, but without hopefully having to turn to, bags of this and bottles of that in order to fertilize them?
I guess my, basic idea is, that, going back to, compost and, organic amendments and, materials that generally improve the health of the soil is a good. place to start. So if you're doing that, you're much less likely to run into specific nutrient problems. it's not to say that you, you may not, and you may need to, provide some curative, treatment for a particular, element.
if you can, maintain a, Healthy amount of organic matter in the soil, you might do that by composting every few years. You might do it by providing bark mulch under the trees that over time is degrading and decomposing and releasing nutrients that are available to the tree. That's a kind of a holistic, I think, easier way to maintain the tree in a good, healthy, Nutritional state.
I
think,
yeah, I was just going to say the other. The other thing is pH. So we talked about the importance there. And that's something that, you need to be aware of. you, you can. create pH problems, by applying some, compost, for example. So if you had a cheap source of, chicken compost from an egg laying operation, that, that stuff is very high in calcium and very high in pH.
So you could create an issue, with, the wrong kind of, compost too.
Exactly. So, yeah, so again, I'd love to plug my course, Soil Essentials for Fruit Trees at learn. orchardpeople. com. There is so much to learn, and it is so fascinating. Soil is so interesting. My first passion was fruit trees, and then I started to learn what's happening in the soil, and I'm like, oh my gosh, that is a whole new world.
And it's a lot of fun. But, Eric, thank you so much. Thank you so much. How can people learn more about you? Have you written any books or are there any articles that we can see or a website you can share?
Yeah, there, my website at, Michigan state university department of horticulture is, still up and, not too active since I've been retired for, several years here.
But most of the early work is, still listed there that people are interested.
Fantastic. And I would love to have you back again. Maybe next time we can talk about different amendments and how things work. but it has been such a pleasure to talk to you and I feel like it's empowering to go through and, just to start observing a little bit more, really paying attention to our fruit trees to, so we can be better, stewards of our trees just by paying attention to them, giving them the love that they need and deserve.
That's exactly. Yeah.
Thank you so much.
Now, if anybody, wants to listen to this show again. Or watch a video version of this show. It is available folks. You can go to orchardpeople. com and click on podcasts and you'll see this podcast. You'll see all the other podcasts I've done. And this is number, I think, 106 or 107.
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I'll see you then. Bye for now.