"For bonsai, it rains two times"

[pandacular]

I have heard the above (purportedly) Japanese expression from time to time. The idea is that you should water your trees a second time after a short period of time (10-30 minutes) to allow water to run through and "prime" the soil to accept water.

This makes enough sense in theory: many materials have hydrophobic properties when completely dry but not when damp. I'm curious if this technique is part of your practice. If so or not, I'd like to hear details about the specifics of the trees and substrates that you are answering for, as well as the results and effects of technique.

 

[roberthu]

I do it every time I water. 2nd round is a must for some of my trees that have not been repotted for over 3 years. I waiting for 5 minutes though and usually the water runs through much quickly and doesn't pool up as much as the first time.

 

[MaciekA]

I study with a teacher who apprenticed in Japan, and I study with one of his apprentices as well. At both teacher's gardens, this is how students and/or apprentices are taught to water.

 

[pandacular]

At both teacher's gardens, this is how students and/or apprentices are taught to water.

I'm curious if there is a reason given for this. If your teacher is who I suspect, there's always a reason given.

 

[MaciekA]

I'm blushing to say that I can't recall any deep explanation (i.e. much deeper than just "yeah this helps make sure the watering is thorough"), and I've sort of overwritten that memory in my head with my own reasoning, which is not too far from yours.

I've seen some severe hydrophobia in trees (paper dry root cores in spite of continuous watering in the growing season and continuous winter rains), particularly in larger Telperion trees, so the threat of getting these details wrong is very real in both high value material and in high value bonsai. I don't think the risk is uniform across my garden though, because I have a lot of things in colanders and coarse media.

If you are thinking a lot about this topic, one thing to also think about is how to rehydrate dry cores of poorly-potted (often slip potted) or simply overdue-for-a-repot trees: Tub immersion. Tub immersion is like a nuclear option equivalent of the first of these "two rains". In my book this also counts as a preventative measure -- root balls that are susceptible to hydrophobic cores (at least in my experience) are also ironically the kind that don't dry out very quickly, so a properly thorough immersion doesn't have to happen often

 

[pandacular]

What you say conforms my suspicion that this technique is primarily aimed at trees with percolation issues, which is consistent with what I've observed in my garden. My trees more due for a repot, especially those potted in organic soils, seem to shrug off the first watering and imbibe the second.

 

[Colorado]

Yes, I always do this. I water all my trees, and then once I’ve hit everything, I go back with a second watering. The second one only takes a few extra minutes since everything is already wet.

I think it just helps make sure that you’re getting a good thorough saturation.

 

[Paradox]

When I hand water, I fill the pot until it drains through then let it drain and do it again at least one more time

 

[Deep Sea Diver]

Hmm… Not totally to do with percolation, it also has to do with the physical qualities of inorganic media…

When a media dries out on top (hopefully only on top) it often becomes hydrophobic, witness the recommendation to grow and maintain moss on top of the media… to help prevent this. It helps, but doesn’t solve errors in timing…

Examples are far ranging, some are worse the otherspeat, wood, kanuma , akadama, LECA like expanded clay materials etc etc

In these cases the first watering tends to not be as complete as on wishes, double with media that is has perc issues and using certain media that requires soaking to properly rewet like Leca and other expanded

 

[Deep Sea Diver]

Uh Oh this is a revised post from my last for clarity and correctness

Hmm… Sometimes things aren’t as simple as we’d like. I’ll take a stab at explaining this in layperson’s terms.

The reason for watering twice has much less to do with poor media percolation per se in that interstitial space is clogged impeding percolation…

….and more to do with the physical qualities of media…(external and internal) and a lot to do with the polar nature of each water molecule.
(Note for this explanation don’t include particles that do not absorb water)

…,And a lot to do with the actual resistance of the dry particles to the penetration of water molecules

When a media dries (hopefully only on top) it can become hydrophobic… throughout the particle.

Witness the wisdom over the years to grow and maintain moss on top of the media… to help prevent loss by evaporation . This helps, but doesn’t solve errors in timing…or hot “drying days”

If hydrophobic outside the media particles can also be dry throughout the particle…this is caused by the polar nature of water molecules drawing other water molecules out to the exterior when evaporating…. sorta of like a chain of water molecules being pulled out of the particles with the drying action of the sun… evaporating the outer particle in turn… and so on…

Examples of media that become strongly or moderately hydrophobic are far ranging, some are worse than others like peat, LECA like expanded clay materials, others wood, kanuma , akadama, etc etc. Particle size also plays in, but I’m not gonna go there it’s late in Eastern Tennessee where I am at present.

Consequently the first watering can have incomplete penetration in the particle as this takes time., think having to overcome resistance all along the way….

This the media requires more water or even soaking to properly rewet particles through and through. ( like Leca and other expanded clay, peat, wood .).

In the case of Media with clogged interstitial spaces…. this prevent percolation and only adds to the issue… impeding water passage, slowing the particles of media from being “filled” with water in regions of the pot..

The time lag allows the particles of media time to help internally absorb the water from the interstitial spaces.

Finally the second watering , hopefully, thoroughly rewets the entire media/root system and “fills” the interstitial spaces, Note quotes.

Wisdom of the ancients. Water, wait, water again.

If not it’s tub soaking time!

I hope that helps.

Cheers
DSD sends

 

[pandacular]

excellent post DSD, thanks so much for never letting me reach a halfway conclusion and working towards a clearer understanding. the more I look at my desire to understand the "why", the more I realize that it is ever expanding complexity through the physics. perhaps it's a fools errand, but I enjoy the search.

Thanks for pulling my eyes down the chemistry level, this is a very interesting topic.

Particle size also plays in, but I’m not gonna go there it’s late in Eastern Tennessee where I am at present.

rain check?

 

[leatherback]

chemistry

fysics I would say

But as for your question, yeah, this is what is my practice too.

 

[Shibui]

I heard that the older Japanese masters taught that bonsai need to be watered 3 times. Once for the leaves, once for the trunk and once for the roots.
Plenty of sound reasons above why the extra watering works.

I also add that leaves on a well ramified bonsai can divert an incredible amount of water away from the pot and soil. In nature this is probably a good thing as rainfall is directed out to the 'drip line' where many feeder roots are in the soil. Bonsai pots are typically smaller than the drip line so pots miss out on that diverted rain water.
If we get rain but less than 6mm (1/4 inch) in summer I still need to water the pots.
It takes quite a lot of rain to penetrate through a dense leaf canopy but that's probably not quiet what this discussion is really about.
Usually water from a hose nozzle penetrates better than gentle summer rain.

 

[Japonicus]

Good read @pandacular
Brings up a current question I have. I think the answer is a vague 24 hrs, but let me ask please...
After spraying the foliage with whatever spray is currently required ie. fungicides or insecticides...
how long should this remain dry to penetrate?

Also, secondly...

Once for the leaves,

I usually, avoid the pine needles. Almost always with any late afternoon waterings as I have been
fighting either needle cast or brown tip blight or both, for the last 2 years.
With juniper, spider mites are discouraged some with leaf waterings, but what about pines?

 

[Japonicus]

EDIT: for pines, I've been using the weather as a gauge for if I need to include the needles of pines.
If it's been very hot, and or very dry, I include the needles, in the mornings. However, I am in a rather humid
location, albeit not nearly as humid as the South, but I am growing some trees that are mountainous
such as mugo and JWP. So typical hot (not very hot) I generally leave the needles dry.
Is this a good disease prevention method, or is it promoting something bad, to leave the needles as dry
as I can?

 

[pandacular]

i had thought about including a discussion about whether we water foliage, but figured it may be too divisive. But since several of us have gone into the fysics of this, i suppose it's fair game!

this is caused by the polar nature of water molecules drawing other water molecules out to the exterior when evaporating…. sorta of like a chain of water molecules being pulled out of the particles with the drying action of the sun… evaporating the outer particle in turn… and so on…

if i understand correctly, this is (part of) the cohesion-tension model of water movement through a tree. one argument i've heard against watering the foliage/misting is that it momentarily breaks (or perhaps stalls) the chain of water molecules, which can cause problems. i'm far from privy to the specifics of how that would work, but it seems reasonable.

of course there are many arguments for watering foliage as well, but i would rather save in depth discussion about watering foliage for another thread (of which there seem to be no shortage)

 

[Wires_Guy_wires]

Try to soak a wet sponge and it floats.
Break the water tension with some soap, and it will sink.

Soil components are like a sponge. If they're dry, they'll repel water because the air trapped in them forms a shield. Once they get wet and the water can manage to go around the air bubbles by soaking into the clay or stone, it moves around the air bubbles and cohesive forces of water push the air out by adhering to the clay/stone and cohering to itself, still leaving some trapped air.

That's the simplest explanation I can give. A balloon doesn't sink unless you open it and replace the air with some water.

I water everything overhead and have never seen fungal issues that caused a problem in the past two years. I think people don't water the foliage because of limescale, that's all there is to it: aesthetics. As a disease preventative method, I'm calling BS. On trees that is.

 

[Michael P]

I do it as needed, that is if the soil repels water on the first attempt. Under current conditions (105 F, 20% RH) I water several times a day. My mix holds enough water to last 24 hours. The additional waterings cool the foliage and the pots and increase humidity at least for a little while. And yes I wet the foliage of everything.

 

[Glaucus]

I think this is a basic principle in watering any potted plant. When it rains, it may rain for hours or even the entire day. So when watering, you water once, let it flow, let it drain, let it soak in. And then you do it again.
You make sure it really gets wet and soaked, and that the water gets everywhere. In between the watering, then is the time it might dry up (assuming it isn't a hot sunny summer day).