Fall fertilization

I wonder what people’s thoughts are regarding applying nitrogen in the fall.
Last year I put urea on some pawpaw, with good results.
Their is conflicting info on this subject.

One theory is that in the fall of the year ,as leafs fall, the nutrients in the leafs are taken back up by the tree and stored during the winter.

The other theory is that it can encourage late growth, and lack of hardyness .
I am of the opinion that if nitrogen is applied late enough ( about the time of leaf fall) it is good
Also remember reading that late foliar urea sprays were more effective.
And can help decompose leafs that have disease on them.

What are your thoughts…opinions …experiences…etc.

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A huge pecan tree no longer alive (lightening hit) we would wait until all the leaves drop and then rake them away, and then as Fall temperatures were a month or weeks away from soil freezing we would broadcast pretty heavily. I recall fertilizing when the ground was frozen too. Snow melt will get the fert. to the roots during warming up cycles so it’s fine to fertilize at that time, too.

The following Spring while dormant we would repeat.

W/o fertilizer the tree health was noticeably not as lush and the nuts were in less quantity. Now this was a 75’ tall tree so fert. became necessary.

What I’m not sure is if fertilizing young trees is necessary.

We could talk soil tests until our heads spin, but, for these older trees a good boost of fertilizer seems a reasonable approach.


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I don’t know if we are talking theories or beliefs. The old belief was that fall fertilization causes a growth reaction that leaves trees vulnerable to winter kill, believe the current theory at least partially based on Whitcomb’s research is by late summer, most species stop responding to N apps that season. If it was dangerous, I suspect lawn companies would be killing off lots of trees with their traditional labor day app of high N fertilizer.

Some of us believe in a split app for fruit trees- early fall (or very late summer) and early spring. Maybe a third app in mid to late spring for trees we are trying to size up quickly.

Cornell believes the fall app is too likely to be lost and also possibly cause environmental damage which may have occurred to a lot of Barkslip’s over-snow apps. They recommend K in the fall and N in the early spring in their general maintenance program for commercial fruit production.

But then, commercial growers often use foliar urea in the spring to make sure spur leaves are rearing to go. I believe that fall soil applied N may do the same thing.

I apply potassium with a 90 day encapsulated urea in late summer or early fall and then give peaches and any other trees I want more vigor from, including nursery trees, more 90 day urea in spring. I “believe” it’s a good method. Actually I generally forget the fall app for peaches because they don’t even seem to respond to it- when they get it, it’s only for the K. This year I went light on the N anyway, going 2-1 K.


Some years we were later than others at getting the job done. We didn’t fertilize over snow but I am in agreeance that fertilizing on frozen ground has a lot of runoff.



I have bought Tree-Tone before and I think they suggest a fall application.

I don’t use high nitrogen, but in October I put Milorganite on the grass, and most of my trees are in the grass, so unlike you I don’t use urine, but do put human poop on them in the fall, and spring too! My neighbhors keep asking me what I use? As my grass is the greenest on the block! Milorganite is awesome! Very cheap too, for suburbia fertilizer. Nothing sold bulk within 50 miles of me. My leaves look good right now, you can see them on my Indian Free in that thread.

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I believe the heavy metals Milorganite contains makes it a no-no for edible crops, though. Digested urban sewage isn’t quite the same as my own urine- I don’t usually flush down my gullet what urbanites flush down their toilets. It also contains contaminants from street gutters. Urine is of different materials than poop in many ways as well. I don’t want my fruit trees growing in soil that produces the “greenest lawn”. That’s why I’ve dialed down heavy mulching for mature trees.

The less available water the soil holds the sweeter the fruit. OM holds more available water than anything else roots grow in. This is a chorus I sing here on a regular basis, but it doesn’t apply to areas that don’t get ample rain during the growing season. You lucky folks have the power of the spigot.

Correct me if I’m wrong about the Milorganite- I haven’t looked into it for years.

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It has been approved by the EPA for vegetable crops, EPA testing shows it has less metals than most if not all lawn fertilizers. It is well within the limit set by the EPA. It is kinda gross and all, but I like the idea of recycling. I’m not sure how they got it so clean? Even California approved use.

I myself much prefer the organic fertilizers, it’s been my observations my plants look best when used. I’m not happy with most chemical types, but I still use them on seedlings or when a plant looks like it needs a boost, it happens from time to time. I didn’t buy into the feed the soil bit, but I’m finding by trying it, that it works, and works well. On trees, I’m not sure as I never have used anything but organics. I remove so much organic material in the form of fruit I feel i have to replace it.


It is cleaner now than in the past because of the de-industrialization of Milwaukee. And general environmental regulations that have been reducing the use of heavy metals in consumer and industrial products since the inception of EPA. The high-temperature drying process likely removes a bunch of organic molecules that folks flush down their toilets and wind up in the sewage through storm drains.

If I can find the stuff, I use Milorganite as a lawn fertilizer.

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Nitrogen is nitrogen once it is available to plants. The advantage of organic fertilizer is strictly long term- gradually building up OM in the soil- IF that serves your needs.

Your observations do not apply to most gardener’s experience that I know of. I have seen many an organic gardener switch to Miracle Grow for their plants in potting soil in the greenhouse or under lights, although an organic quick release of similar qualities should perform as well.

As I’ve often stated, organic release increases as soils warm and cool soils often don’t release enough P for good early growth- the same thing with N.

My closest gardening friend is a life-time organic gardener and quite skilled at it, but he sees the difference in my vegetables. Once they go into soil, I don’t use synthetic, but as you know, urine converts to urea in about 2 days and from there, quickly to ammonium, which is quick enough. By summer I lay off the N sources, including urine for vegetables.

Nursery people generally rely on synthetic N simply because the result is quicker growth. I used to think organic worked as well until I actually compared results- I’d use alfalfa cubes which have a lot of N in them, but now that I use encapsulated urea I get significantly better growth, especially from my peach whips.

I started gardening organically in about 1967 and didn’t switch to using some synthetic materials until the 90’s.

I guess my main point ( question ? ) of this post is ;

Is late fall a efficient time of year to apply nitrogen, if you are really trying to push growth.?


Has anyone had winter damage by fall application of nitrogen ?

Fall applied N can be effective but it needs to be applied early enough that the plant can take it up before winter. The plant needs leaves in order to take up water and the N. In most cases the tree probably won’t be spurred into growth. But the timing of application could be critical.

I say why take any chances especially in a climate with wet winters. Much of that fall applied N can end up in the ground water or running down a river next spring. It’s not necessary. Apply in spring when the plant needs it.

Applying N in winter with snow or frozen ground is a bad idea. Much of the N will end up in the nearest river. It’s a major problem on the Mississippi and many other rivers.


agree with fruitnut. However, if the soil is not frozen and liquid urea penetrates the soil, the tree will not care. In spring the urea will be 2 ft down, which is just fine for the tree.

Come to think of it, that is probably the reason for N-fertilization in fall. Make sure the grass, and its relatively short roots, do not get a lot of it, by making it percolate past their roots before growing season.

A clarification on the processes that @Fruitnut’s comment is based on.

Urea is rapidly converted to ammonium by soil bacteria. In high organic matter and/or clay soils ammonium is relatively immobile due to exchange with other positive ions e.g. Na/K/Ca/Mg. Once in soil, if the temperature is above 50F, ammonium is converted to nitrate by microbes. Nitrate does not bind to soils so it leaches to groundwater and runs off.

The problem would be somewhat intensified in the ideal orchard soil because we want porous, well draining soils for our orchards or strive to provide them in other ways (mounds, raised plantings, etc). Well drained soils will lose ammonium to nitrification to nitrate faster than poorly drained soils.


The roots won’t likely be functioning 2 feet down in the spring and I don’t believe the N would remain urea even in cool soil by then- the only point to fall fertilization I see is for the N to be picked up by the tree at that time so it is in the spur buds at first growth for bearing apple and pear trees.

Most root activity, including N absorption, occurs in the top 12 to 18 inches of soil for trees, with fine root growth highest near the surface of the soil in spring, because it tends to be warmer and better aerated early in the season.

Fruitnuts warnings would seem to apply to careless apps when trees are shutting down for winter. I believe there is a big difference between early and mid-fall on in terms of potential loss of N.

Carl Whitcomb is very qualified in advising how to establish fastest growth in nursery production of trees- for tree growth he doesn’t advise any apps after Sept, and his experience and research is in Oklahoma conditions- but he stresses the importance of soil texture in determining the frequency of application with sandy soils needing more frequent and lighter apps then clays.

This would indicate to me, that the nursery trade has found no benefit from fall applications to spur more vigorous growth, so if that’s your primary goal I’d agree with FN and wait until spring- unless you soil tends to stay very cool and wet in early spring but is warmer and better aerated in early fall. In those conditions a split early fall and mid-spring app might be more effective with additional applications made throughout the growing season.

In porous soils encapsulated nitrogen might provide the best results- at least for spring and early summer fertilization.


Yes, as I have to leave so often during the summer. Probably why I like the organic products. As far as building the soil, in my raiied beds I lose 1-3 inches a year of organic mass. It’s amazing how much plants pull out of the ground. You can watch the bed soil levels go down. I refill in the fall. Whatever I have, old potting soil, leaves, grass, cardboard etc. I try to balance the green and the brown,

I do for seedlings under lights too. I have uses for chemical fertilizers, just I tend to use a lot less these days. The quick release organics are too expensive per dose. I don’t use Miracle Grow, i prefer various products, like Dynamite time release (9 months), most plants require a 3-1-2 NPK, this is in general and Dynamite and also Foliage Pro have these ratios, and both have full trace elements. I like to use the the time release on seedlings or rooted cuttings I sell or trade. I use the Foliage Pro for veggie seedlings I start indoors. I don’t really see much if any difference on your methods and mine. I use what works well, I really don’t care about organic or not, I care what fits my needs, and I’m finding it’s mostly organics. I also use chemical at the end of the year for some things, as organics can last for a long time, and I only need the nitrogen for short term. Like on pepper plants, I push them with chemicals to produce to the last minute. When cooking I often go out and pick fresh, like peppers and cherry tomatoes for a salad tonight, Lettuce also. All harvested and served. We had ravioli in homemade tomato sauce with heavy amounts of hardneck garlic from the garden and fresh basil from the garden too. I try to do this daily. At least one item from the garden daily. I also served smoothies with Nectaplum and Arctic Glo nectarines (fantastic!). A good day! Yeah peppers in the salad were Yellow Monster, what a great pepper plant. It produces oversized yellow thick walled bell peppers that are very sweet, as sweet as those little peppers they sell. The plant produces late, but many peppers, very impressive, love this one. It also is drought tolerant (peppers will not shrivel in dry conditions), very resistant to BER, and foliage diseases (never seen any). Spanish Mammoth is another great cultivar with the same features except the peppers are red.

No just provide food for the plant to store as winter reserves. A weak plant is more likely to succumb. It’s hard to push growth late as the plant can tell what is coming. If in warmer temps, like in a greenhouse or additional lighting, yes they will keep growing.

How should I rephrase that?
I am not trying to push any growth this fall ,rather in the spring.
And , ?
Spring" IS" the most efficient time to apply “N”.
So I just wonder about getting a optimal level of fertility into the plant in the fall ,so it can hit the ground running in the spring,without sacrificing hardiness.

I use a slow release like cow manure that is there and stays there. The bad thing about chemical fertilizer is it’s all there at once. The plants use it or lose it. Like @fruitnut said

I put wood chips over the top of the cow manure and reap the benefits of that for years. I’m not knocking chemical fertilizer but if you don’t time it right it’s a very expensive mistake.


I believe you are witnessing the results of digestion of your organic matter by bacteria, fungus and even earthworms breaking down the carbon bonds. Plants may be adding as much as they take with the volume of their roots that are mostly water.


Yes, you are right, seem like I have a hoard of earthworms for sure, never saw so many. They even get into my containers. Noticed a few up potting figs. Also some is to erosion, soil being splashed out when raining, not much, but it happens, I have a lot of fill material this year as I have some aging soil in many containers I plan to recycle. I will be growing fewer containers as I transfer some to the ground. Eliminating a lot of plants this fall too. Streamlining to what works best around here. It has been a fantastic growing season. I had some losses too, but the harvest has been wonderful. Really impressed with some hardneck and softneck garlic varieties I tried, beautiful bulbs and the flavor is outstanding.
I’ll be planting out in a couple of weeks for next year. I’'m moving some black currants to the ground from large containers. they grow well in containers, but i want the largest plants possible. Turns out my wife loves black currants, was surprised, as I do too. She usually goes for the sugar crops.