Rookie mistake

[Lazylightningny]

I've been lax on this site lately, but not lax in the bonsai garden. I managed to kill half of my plants this summer, probably a good 25 plants, by fertilizing with Miracle-Gro in temperatures over 90 degrees. I got up late one saturday last july, and started fertilizing at 11 or so. The temp was already over 90; it was during one of those heat spells we had here in the NE. Some species showed an immediate decline, others took longer. Some of those plants had Osmocote in them as well. As I found out later, after extensive research, the release of nutrients in Osmocote spikes dramatically in temps over 90. So, lesson learned. Let this be a lesson to other newbs as well.

I still think Miracle-Gro has it's place, in the spring, before temps heat up, to encourage heavy growth in developing plants. After that, however, switch to poo balls or a weekly fish emultion/kelp mixture.

 

[Dav4]

I used miracle gro every 7-10 days through the summer...we had about 90 days that were 90 F or warmer....no problems w/ root burn. I'd look to the osmocote.

 

[thumblessprimate1]

I've had no problems using Miracle Gro in temps above 90*F or even 100.

 

[coh]

Yeah, how much did you apply? I use miracle-gro or other powdered inorganic fertilizers all summer and have never had a problem like that. I only use osmocote type products on nursery stock, not trees in bonsai containers where fertilizer control is more important.

 

[0soyoung]

So, you know as a fact that none of your trees' roots got hotter than 95F? Roots don't grow at these high temperatures.
You also know that your dead trees' roots didn't get close to 115F that is fatal to all tree roots?

Something like one-half teaspoon of Osmocote Plus per gallon of substrate is about all that is needed to have healthy vigorous trees; apply once or twice a year and then fuggitaboutit. IMHO, don't use Osmocote if you, instead, prefer the other ferts you've played with. Osmocote release increases with temperature pretty much matching the needs of your trees which grow faster with increasing temperature (up to a point).

 

[Lazylightningny]

Yeah, how much did you apply? I use miracle-gro or other powdered inorganic fertilizers all summer and have never had a problem like that. I only use osmocote type products on nursery stock, not trees in bonsai containers where fertilizer control is more important.

Miracle-Gro used at a rate of 1 tablespoon/gallon weekly

 

[JoeR]

I had a similar issue with chemical ferts last spring too. Killed all my pines and various other deciduous too

 

[0soyoung]

I had a similar issue with chemical ferts last spring too. Killed all my pines and various other deciduous too

How did you determine that it was due to chem ferts and not something else?

 

[JoeR]

How did you determine that it was due to chem ferts and not something else?

Reasonable problem solving?


If you notice a dramatic change in the appearance of ~15 trees in a matter of 24-48 hours, and the only variable that changed is fertilizer, you can conclude that it was the fertilizer. Normally, conifers take a long time to show signs of stress (and they did take longer than the deciduous trees), but within 48 hours you could feel changes in the needles. Maybe a week or so later, they were completely brown. It was due to the fertilizer salt,

 

[Lazylightningny]

None of these trees were in bonsai pots; all still very much in development phase. I'm glad to hear that you use Miracle-Gro in hot temperatures, but do you fertilize when it's that hot, or in the morning before the temps get that high?

I'm sure the problem was in using both Osmocote and Miracle-Gro. My thought process was to have a daily slow-release fertilizer, with weekly powdered fertilizer, but it was obviously too much in the warmer weather.

So, you know as a fact that none of your trees' roots got hotter than 95F? Roots don't grow at these high temperatures.
You also know that your dead trees' roots didn't get close to 115F that is fatal to all tree roots?

Something like one-half teaspoon of Osmocote Plus per gallon of substrate is about all that is needed to have healthy vigorous trees; apply once or twice a year and then fuggitaboutit. IMHO, don't use Osmocote if you, instead, prefer the other ferts you've played with. Osmocote release increases with temperature pretty much matching the needs of your trees which grow faster with increasing temperature (up to a point).

Our temps never reached 100 degrees, but were in the 90s. I concluded that they were in summer dormancy, and that fertilizer was the cause of the problem.

 

[Lazylightningny]

I had a similar issue with chemical ferts last spring too. Killed all my pines and various other deciduous too

Joe, were you fertilizing at the recommended strength?

 

[JoeR]

Joe, were you fertilizing at the recommended strength?

The instructions were for trees and shrubs in the ground, so I had to guestimate=probably not. I tried to stay on the conservative side when I applied it, but it still was too much.

 

[coh]

The instructions were for trees and shrubs in the ground, so I had to guestimate=probably not. I tried to stay on the conservative side when I applied it, but it still was too much.

So how much did you use? What were the weather conditions? Did you apply to dry soil, or did you water first?

We have people (such as Walter Pall) who say they use up to 5x the recommended dose of inorganic fertilizers, so why are a few of you having so many problems?

When the weather is hot I usually fertilize late in the day, after watering. Why...I think if one fertilizes early on a hot day, especially if the soil is dry or the plants are already water stressed, there is a risk of too much fertilizer being drawn into the plant as it takes in water. Or, if the plant takes in water but leaves the fertilizer behind (I'm not really sure how all that works), it is possible the concentration of salts in the container could increase and cause problems. Probably safest would be to cut back the fertilizer rate when it's really hot.

My fertilizer rate is in the range of 1-2 tsp/gal.

 

[sorce]

A little bit of La La.....

And some hocus pocus.

Kern Ferk the Cheeseburger.

On rye.

Sorce

 

[Lazylightningny]

A little bit of La La.....

And some hocus pocus.

Kern Ferk the Cheeseburger.

On rye.

Sorce

I knew you'd have the answer, Sorce.

 

[Lazylightningny]

So how much did you use? What were the weather conditions? Did you apply to dry soil, or did you water first?

Is it recommended to water the plants first before fertilizing? I've wondered if that had an effect. Does the watering beforehand open "channels" in the root hairs?

When the weather is hot I usually fertilize late in the day, after watering. Why...I think if one fertilizes early on a hot day, especially if the soil is dry or the plants are already water stressed, there is a risk of too much fertilizer being drawn into the plant as it takes in water. Or, if the plant takes in water but leaves the fertilizer behind (I'm not really sure how all that works), it is possible the concentration of salts in the container could increase and cause problems. Probably safest would be to cut back the fertilizer rate when it's really hot.

Are you saying to fertilize in the evening, after the temps have cooled off a little?

My fertilizer rate is in the range of 1-2 tsp/gal.

I'm fertilizing at only 1 tsp/gal.
Tsp or Tbsp??? Now I'm not sure. I'm using 1 scoop of the bigger end of the green spoon that comes with Miracle-Gro, per gallon. At what rates do others use Miracle-Gro?

 

[0soyoung]

None of these trees were in bonsai pots; all still very much in development phase.
Our temps never reached 100 degrees, but were in the 90s. I concluded that they were in summer dormancy, and that fertilizer was the cause of the problem.

The soil in any pot in the sun can become quite a bit hotter than the general air temperature - the drier the soil, the higher the root temperatures can be; even worse in black plastic pots. Borrow the meat thermometer from your kitchen or buy another dozen (at less than $15 a pop, why not?) and stick it (them) in the roots to see how hot the roots really are.

I think if one fertilizes early on a hot day, especially if the soil is dry or the plants are already water stressed, there is a risk of too much fertilizer being drawn into the plant as it takes in water.

Minerals are loaded into root cells by an active life process. Water is loaded largely by simple passive osmosis: water goes in if there is less water in the root than in the substrate; water goes in if it is saltier in the root than in the substrate.

Hence, more salt outside the roots draws water out of them = fertilizer 'burn'.

If you notice a dramatic change in the appearance of ~15 trees in a matter of 24-48 hours, and the only variable that changed is fertilizer, you can conclude that it was the fertilizer.

Pretty convincing. I'm surprised that you didn't think to flood the pots. I mean water, water, and water again to flush the fert out when you saw the clear indications after 24 hours. You might still have all or at least some of those 15 or so trees. Ah well, we all have our deer-in-the-headlights moments.

 

[Carol 83]

A little bit of La La.....

And some hocus pocus.

Kern Ferk the Cheeseburger.

On rye.

Sorce

Put the pipe down, man.

 

[coh]

Is it recommended to water the plants first before fertilizing? I've wondered if that had an effect. Does the watering beforehand open "channels" in the root hairs?

I don't know, there was a thread earlier in the year where people were discussing whether to water before fertilizing. As with most things, there were people who watered first, and others who didn't. It may not matter, or there may be situations where it does. How's that for a useless answer?

Are you saying to fertilize in the evening, after the temps have cooled off a little?

Yes, that's what I do. That doesn't mean you have to do that. I've never had a tree die from a fertilizer issue.

I'm fertilizing at only 1 tsp/gal.
Tsp or Tbsp??? Now I'm not sure. I'm using 1 scoop of the bigger end of the green spoon that comes with Miracle-Gro, per gallon. At what rates do others use Miracle-Gro?

You'll have to look at that, it might be labeled. If not, use a kitchen tablespoon to compare. I'm guessing the larger size is a tablespoon.

BTW, my main inorganic fertilizer lately hasn't been miracle gro, I've been using a grow more product because it is urea free. But it's similar and I have used miracle gro and miracid.

Minerals are loaded into root cells by an active life process. Water is loaded largely by simple passive osmosis: water goes in if there is less water in the root than in the substrate; water goes in if it is saltier in the root than in the substrate.

Hence, more salt outside the roots draws water out of them = fertilizer 'burn'.

I seem to recall reading somewhere that some of the fertilizer substances - don't remember which - are carried passively into the roots along with the water. Maybe I'm not remembering that right, but that been one of my reasons for not fertilizing a dry plant or in the hottest part of the day. I don't have a background in plant physiology or horticulture, though, so I'm not as informed about these details as you seem to be.

 

[jeremy_norbury]

A little bit of La La.....

And some hocus pocus.

Kern Ferk the Cheeseburger.

On rye.

Sorce

The voice of reason shows up.