I live in central Illinois and have a few trees growing very well. I seem to fertilize to far in to the fall and the new growth doesn’t harden off and dies over winter. So at what point do I stop nitrogen and just feed P-K to help store energy and nutrients. What is the best thing to feed at that time. Thanks.
When to stop feeding nitrogen
- Thread starter Rod
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rockm
Spuds Moyogi
The "stop feeding nitrogen in the fall" thing is largely a myth. Doesn't really matter if you use low N fert or regular fertilizer. The tree uses what it needs and isn't "force fed" anything.
What is more pertinent is when you're pruning and fertilizing overall, both of which can stimulate late new new growth. The later the pruning, pinching etc is done, the more chance you will get late shoots that don't harden off before the first frosts.
Tidal Bonsai
Omono
As @rockm said, the nitrogen stimulates growth thing is a disproven belief that still floats around bonsai circles. But you know what stimulates growth 100%… late season pruning!!!
In Zone 7a where I am, I stop pruning deciduous trees around the first week in August to give my trees time to harden off the new growth. Since you are a full zone colder, this week may be your time to get in the last round of pruning until fall.
In Zone 7a where I am, I stop pruning deciduous trees around the first week in August to give my trees time to harden off the new growth. Since you are a full zone colder, this week may be your time to get in the last round of pruning until fall.
Glaucus
Omono
I don't think it is proven that nitrogen doesn't stimulate vegetative or elongated growth. Yes, the plant uses what it needs. But if there is no nitrogen, it can't take it and it will grow differently. If the soil doesn't contain any nitrogen, how does say a pine or maple grow 60cm new shoots in growing season? It can't.
As for not feeding nitrogen in autumn, when the plant isn't really elongating new growth anymore, why fertilize with high N? As for how much the NPK ratio can modulate growth patterns of a plant, not too sure. That may be a myth. Or may depend on the species.
A plant isn't going to 'take take take' all the nitrogen it can, until it hits a wall and there is nothing left and go from vigorous healthy growth to a nutrient deficiency.. It will modulate it's growth behaviour before it exhausts the soil.
A potted plant will grow completely different if A) it has no space for new roots & there's no N fertilizer compared to B) there is a ton of new space for new roots & there is plenty of nitrogen.
If there is a paper that 'debunks' this, I'd like to read it.
It would be cool if there is a paper somewhere that addresses harding off new growth & nitrogen in autumn & winter hardiness.
I feel that with azaleas I definitely see plants (not bonsai) that have grown strongly because of a repot, fertilizer, plenty of space for new roots, do not harden off their growth as quickly in autumn. And those water sprout shoots then get damaged by the freezing temperatures. While an azalea of the same or similar variety in a status quo pot will not have this issue at all.
As for not feeding nitrogen in autumn, when the plant isn't really elongating new growth anymore, why fertilize with high N? As for how much the NPK ratio can modulate growth patterns of a plant, not too sure. That may be a myth. Or may depend on the species.
A plant isn't going to 'take take take' all the nitrogen it can, until it hits a wall and there is nothing left and go from vigorous healthy growth to a nutrient deficiency.. It will modulate it's growth behaviour before it exhausts the soil.
A potted plant will grow completely different if A) it has no space for new roots & there's no N fertilizer compared to B) there is a ton of new space for new roots & there is plenty of nitrogen.
If there is a paper that 'debunks' this, I'd like to read it.
It would be cool if there is a paper somewhere that addresses harding off new growth & nitrogen in autumn & winter hardiness.
I feel that with azaleas I definitely see plants (not bonsai) that have grown strongly because of a repot, fertilizer, plenty of space for new roots, do not harden off their growth as quickly in autumn. And those water sprout shoots then get damaged by the freezing temperatures. While an azalea of the same or similar variety in a status quo pot will not have this issue at all.
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Glaucus
Omono
"Seedlings were grown under two N fertilization regimes (6 and 100 mg N per plant)"
"However, high N fertilization also increased frost damage (24%) and decreased plasmalemma stability to dehydration (9%)."
"However, high N fertilization also increased frost damage (24%) and decreased plasmalemma stability to dehydration (9%)."
Tidal Bonsai
Omono
Understandable that you want proof from someone besides a random guy on the internet. Look at Michael Hagedorn’s book, Bonsai Heresy from 2020 starting on page 181. He discusses the myth of nitrogen in fall stimulating new growth and cites a scientific study on it:
Try it yourself, apply your normal NPK fertilizer all fall without pruning the tree and see what happens. I have been doing it for 7 years and nothing new has ever sprouted. Pruning stimulates new growth in the fall, not Nitrogen.
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rockm
Spuds Moyogi
Hagedorm cites several studies in his book. I haven’t rummaged through his bibliography to cite them but suffice to say there is substantial evidence that limiting N in the fall is not a thing.
Glaucus
Omono
This is a review paper that cites both the paper I found and the one Hagedorn cited:
"The key finding is that in 40% of reported cases nitrogen supply increased frost hardiness, while in 29% of cases nitrogen had no effect on frost hardiness. Together these findings comprise 69%, implying that in the majority of cases nitrogen additions are not deleterious but actually improve frost hardiness, especially in autumn."
"The key finding is that in 40% of reported cases nitrogen supply increased frost hardiness, while in 29% of cases nitrogen had no effect on frost hardiness. Together these findings comprise 69%, implying that in the majority of cases nitrogen additions are not deleterious but actually improve frost hardiness, especially in autumn."
rockm
Spuds Moyogi
Tidal Bonsai
Omono
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