Overwatering: myth or monster?

[Lars Grimm]

Hi All,

The topic of overwatering still confuses me at times. Reading these forums and blogs there are repeated references to the dangers of overwatering, as a cause of root rot, micronutrient starvation, and . But also, there are established professionals who argue that in a modern substrate overwatering is impossible.
Walter Pall article on overwatering
Harry Harrington article on watering

I understand this will be dependent on soil composition, but if we limit ourselves to the common Boon's mix of akadama, pumice, and lava rock with no organics then soil over saturation should not be a problem.

Last year I struggled with what I assumed was chlorosis on an Amur Maple in later Summer that did not respond to soil and foliar applications of chelated iron and magnesium. Here is the link to my post from last year with a picture.


This year I am starting to have the same problems with some tridents in late Summer which are being fed with green dream, pH 7.2 water, and have not responded to supplemental iron or magnesium.

From my reading, overwatering can be a culprit as it reduces availability of iron. I admit I tend to over water as work/kid get in they way of being able to water on a more tailored schedule. But, if overwatering is a myth, where does that leave me....

Thanks,
Lars

 

[M. Frary]

I've never had an overwatering problem but then again I don't use akadam. Maybe it is retaining too much water.

 

[Giga]

There may be something else that's going on. I have sometree's in the ground,in potting soil, and most all my tree's in a good bonsai soil. I water all them 2 - 3 times a day and never have a water, root rot issue. Only my white pine I have to watch how much I water. Are these in full sun, partial sun, or shade?

 

[Dav4]

In my experience, pot size and shape play a pretty large role in what water does inside a pot filled with aggregate soil. The only trees I've ever had issues with "overwatering" were in shallow pots.

 

[Lars Grimm]

There may be something else that's going on. I have sometree's in the ground,in potting soil, and most all my tree's in a good bonsai soil. I water all them 2 - 3 times a day and never have a water, root rot issue. Only my white pine I have to watch how much I water. Are these in full sun, partial sun, or shade?

Full sun for about 5-6 hours per day.

 

[Lars Grimm]

In my experience, pot size and shape play a pretty large role in what water does inside a pot filled with aggregate soil. The only trees I've ever had issues with "overwatering" were in shallow pots.

Hmm, the exact opposite of shallow. The Amur was in a grow bag and the trident is in a large wooden box. I would have thought the overwatering would be more of a problem in deeper containers.

 

[BrianBay9]

Walter Pall also combines heavy and frequent fertilization with the inorganic soil and daily watering. Are you sure you're fertilizing enough?

 

[rockm]

Hmm, the exact opposite of shallow. The Amur was in a grow bag and the trident is in a large wooden box. I would have thought the overwatering would be more of a problem in deeper containers.

Both are true. Shallow pots are notorious for poor to very poor drainage, because they don't pull water through as effectively as a deeper one. Not sure of how to explain the exact physics involved, but basically, the water column in a deeper pot has more pressure behind it than a shallower one, which tends to "push" more water out of, as well as draw air into the soil.

Deep pots are deceptive in that they have a larger soil volume that dries slowly in the interior.

Both issues increase with the shallowness and deepness of the individual container.

 

[Lars Grimm]

Walter Pall also combines heavy and frequent fertilization with the inorganic soil and daily watering. Are you sure you're fertilizing enough?

These are both pretty vigorous species (Amur and Trident) so it is possible they are outstripping resources by the end of Summer. But, I would have expected the plants to then perk up after an added foliar and soil drench of fertilizer.

 

[Lars Grimm]

Both are true. Shallow pots are notorious for poor to very poor drainage, because they don't pull water through as effectively as a deeper one. Not sure of how to explain the exact physics involved, but basically, the water column in a deeper pot has more pressure behind it than a shallower one, which tends to "push" more water out of, as well as draw air into the soil.

Deep pots are deceptive in that they have a larger soil volume that dries slowly in the interior.

Both issues increase with the shallowness and deepness of the individual container.

Good point. I'd forgotten about the whole capillary effect of water availability.

 

[TomB]

Have you compared your Trident (not the Amur) leaves with Smoke's recent post on fungal issues? I wonder if that could be your issue.

 

[rockm]

What is the supplemental Magnesium? I've been giving my amurs a twice monthly dose of Epsom salt.

 

[Lars Grimm]

Have you compared your Trident (not the Amur) leaves with Smoke's recent post on fungal issues? I wonder if that could be your issue.

I recently read, and reread, and reread, that excellent post. The trident is dealing with some fungal issues. I was not as diligent about preventative spraying this year unfortunately. The leaf discoloration looks a little different than fungal to my eyes though.

 

[Lars Grimm]

What is the supplemental Magnesium? I've been giving my amurs a twice monthly dose of Epsom salt.

That's exactly what I was using.

 

[Dav4]

Hmm, the exact opposite of shallow. The Amur was in a grow bag and the trident is in a large wooden box. I would have thought the overwatering would be more of a problem in deeper containers.

It has to do with perched water tables. Shallow pots just don't drain as well as deeper pots due to the perched water table affect https://gardening.stackexchange.com/questions/13774/what-is-a-perched-water-table . Deeper pots have a larger soil volume that takes longer to dry out, but in my experience, tree roots are more likely to quickly grow into and colonize the soil of deeper pots if it's an appropriately sized tree for the given pot. Fwiw, I didn't think that an excessively shallow pot was your issue but thought I'd mention it in the context of the thread's op.

 

[sorce]

Yes over watering is real.

The best question I think that we should ask then is....

What can I do to use this to my advantage?

Storytime....

Recently, when I unduffed my smoke tree...I put DE in the top inch to recover the keeper roots.

After hearing about how smoke trees like it dryer, and after doing this same thing to a couple boxwoods....

I got to thinking about how that top soil where you want your good surface roots, will then dry faster/drain better, than that below it, the part that we will cut off anyway!

More perfect.....to further absolutely isolate the bottom section by cutting a clear one inch ring of roots out....placing an isolation disk there if necessary, preferably foam insulation, or something that floats.

Then you can just throw that bitch in a pond and
Let the bottom rot away, or continue to feed the top.
Hydro.

Or both....

Then when you go back....
Remove the foam...
Slice it off...
Pot it up.

Also....

I have been over watering the hell out of my spruce.
Found that out when I recently repotted it.
Almost Everything in the bottom 6 or 8 inches of the pot was so black and dead it just fell out.

Crazy thing is....this has been one of my healthiest, most vigorous trees for 2 seasons now! That's 2 gangster ass winters too!

Hmmmmmm....

The last layer of uppotting soil at the top 2 inches of the pot held what was a near coveted matt of fine feeder roots.

Jury is still out with what turned out to be a very aggressive first spruce repot ever, and in summer!

But the signs say we CAN utilize rot.

Anyway...

It is real.
Know thy enemy.
Use their power against them!

How do we turn a problem into a benefit?

Sorce

 

[clive bennett]

W Paul has it right , but you have to follow all the advice he gives no organics , so no Acadama, ( turns to mud in the UK in a year, or two at best) and loads of feed, it all leads to lots of growth and hence more frequent repottingh

 

[Eric Group]

Hi All,

The topic of overwatering still confuses me at times. Reading these forums and blogs there are repeated references to the dangers of overwatering, as a cause of root rot, micronutrient starvation, and . But also, there are established professionals who argue that in a modern substrate overwatering is impossible.
Walter Pall article on overwatering
Harry Harrington article on watering

I understand this will be dependent on soil composition, but if we limit ourselves to the common Boon's mix of akadama, pumice, and lava rock with no organics then soil over saturation should not be a problem.

Last year I struggled with what I assumed was chlorosis on an Amur Maple in later Summer that did not respond to soil and foliar applications of chelated iron and magnesium. Here is the link to my post from last year with a picture.
View attachment 157749

This year I am starting to have the same problems with some tridents in late Summer which are being fed with green dream, pH 7.2 water, and have not responded to supplemental iron or magnesium.

From my reading, overwatering can be a culprit as it reduces availability of iron. I admit I tend to over water as work/kid get in they way of being able to water on a more tailored schedule. But, if overwatering is a myth, where does that leave me....

Thanks,
Lars

Over watering is not a mythical issue, more- it is a myth to think inorganic soils are a requirement or need for healthy plants. It can cause problems to dramatically over water, but just a little more only leads to more growth. Root rot is generally caused from STAGNANT water- poor draining soils/ pots or really soggy soils that never dry out much...

A free draining substrate- be it inorganic or bark and peat with some perlite- is hard to over water, and you get healthier roots by flushing stagnant air and water frequently! Daily preferably during the growing season.

 

[Lars Grimm]

W Paul has it right , but you have to follow all the advice he gives no organics , so no Acadama, ( turns to mud in the UK in a year, or two at best) and loads of feed, it all leads to lots of growth and hence more frequent repottingh

Akadama is not organic, but Walter Pall also does add organics. http://walter-pall-bonsai.blogspot.com/2010/06/feeding-substrate-and-watering-english.html

 

[Lars Grimm]

Over watering is not a mythical issue, more- it is a myth to think inorganic soils are a requirement or need for healthy plants. It can cause problems to dramatically over water, but just a little more only leads to more growth. Root rot is generally caused from STAGNANT water- poor draining soils/ pots or really soggy soils that never dry out much...

A free draining substrate- be it inorganic or bark and peat with some perlite- is hard to over water, and you get healthier roots by flushing stagnant air and water frequently! Daily preferably during the growing season.

Eric, you live in a similar climate to me. Have you ever noticed the same appearance on the leaves of your tridents?