Rainwater seems to make a difference

[Joe Dupre']

Anyone else notice after a big rainstorm that their bonsai seem to explode with growth? We just a had a few hour gully washer here, and it seems there is observable growth since this morning! I've kinda noticed a bit of difference in the past, but I have a newly collected sweet gum whose buds have seemingly doubled in size since this morning. I've been watering with tap water for these last 4 years but I may switch to rainwater. Goodness knows, we have an abundance of rainwater in South Louisiana.

 

[Starfox]

Absolutely, admittedly it doesn't rain a lot here but we had over half a years rainfall over 2 days on Easter. Now everything is popping, the 3 ginkgos in my forest that hadn't moved are all pushing green. Flowers are a bursting and it's generally a good time for observing growth, love it.
We also get a reasonable deposit of Saharan dust when it rains, not sure if it brings anything beneficial with it but it sure does make a mess.

 

[sorce]

I believe it to be the longevity of the watering.
No rain particularly.

Like the plant knows, in order to prevent root rot/ rid itself of all that water, it grows more to purposely have more leaves with which to remove or utilize that excess water.

Remember only we are concerned with keeping this growth, a tree in the wild only needs these leaves temporarily.

Sorce

 

[amatbrewer]

Anyone else notice after a big rainstorm that their bonsai seem to explode with growth? We just a had a few hour gully washer here, and it seems there is observable growth since this morning! I've kinda noticed a bit of difference in the past, but I have a newly collected sweet gum whose buds have seemingly doubled in size since this morning. I've been watering with tap water for these last 4 years but I may switch to rainwater. Goodness knows, we have an abundance of rainwater in South Louisiana.

I am not saying you are right or wrong, only that aside for the mentioned correlation, what evidence do you have that it is the rain water and not some other factor (or combination of factors) that might be the cause of the observed phenomenon?

Have you ever heard the saying: Correlation does not imply causation?
Causation is an observation of how strongly a changes in a pair of variables are linearly related and change together. While causation takes it a step further and says that any change to one variable will CAUSE a change in another.
Here is a nifty graphic indicating the concept, from back when people were quite sure bad smells cause disease, so obviously good smells would prevent them. [Familiar with the song Ring around the rosies?]

I recall a story I heard a long time ago that goes something along the lines of; A man looking through a small gap in a fence sees a dog walk past and proclaims: "Ah, ha! The nose CAUSES the tail!"

Sorry to belabor the point but this is kind of a pet peeve of mine that I deal with at work almost every day: "It was windy yesterday and I dropped a call. So the wind must affect the signal." Which is the kind of statement that inevitably leads me to another favorite saying: Stress is the result of the brains ability to overcome the bodies desire to choke the living crap out of someone who desperately deserves it.

 

[chansen]

Anyone else notice after a big rainstorm that their bonsai seem to explode with growth? We just a had a few hour gully washer here, and it seems there is observable growth since this morning! I've kinda noticed a bit of difference in the past, but I have a newly collected sweet gum whose buds have seemingly doubled in size since this morning. I've been watering with tap water for these last 4 years but I may switch to rainwater. Goodness knows, we have an abundance of rainwater in South Louisiana.

Have you ever tested your tap water for both pH and TDS? I switched to RO water a while ago, and it makes a difference. I'd rely heavily on the knowledge of those much smarter than I, but my guess is the lower pH in rainwater vs. tap makes nutrients more readily available to the plant.

 

[GGB]

I was going to tag @sorce but he beat me here. His sprinkler system caused strong growth last year and I've been thinking about it since. I also believe it's about the longevity of the rain. Because I ONLY water my bonsai with rain water and they aren't doing anything special. I have a small collection so it's easy to collect rain in buckets. especially last year PA was wet. Have yet to set up a sprinkler system and check the "prolonged water" theory. Of course then it wouldn't be rainwater so the verdict might still be out

 

[Joe Dupre']

A couple of more thoughts........ It may have something to do with the rain drops stimulating the bark and leaves.......or it may have something to do with increased ions. And still more............ prolonged rain may greatly increase the exchange of air within the soil. Prolonged rain may flush harmful tap water impurities out of the pot. All food for thought, I believe.

 

[penumbra]

It is actually pretty common knowledge in the horticulture field that rainwater carries atmospheric nitrogen, particularly when lighting and thunder are involved. I can't site sources here and know because I never researched the topic. I first came across this information from a nurseryman I worked for when I was 13 years old, almost 57 years ago. This has been verbally confirmed no less than a couple dozen times over the years I have worked in the field. There may well be other factors at work but this is the primary one.

 

[Shibui]

I also thought that rain must supply additional N. I assumed that N evaporates from the water after a while because rainwater from the tank does not have the same effect as rain direct from the sky. Maybe someone can help with research results?
Will need to consider Sorce's theory on duration of the watering.......

 

[fredman]

rainwater carries atmospheric nitrogen

Yep rainwater brings nitrogen.

 

[Zach Smith]

Most tap water has been pH-adjusted in order to protect the equipment used to pump and transport it. Ours where I am runs about 8.2. Most (but not all) plants don't like alkaline pH. If you experience two weeks or more without rain, your trees will suffer as the buffering capacity of the soil is overcome. What you want is good old rain. The pH will tend to be slightly acidic, and that's how God intended it. Your trees will definitely improve if you get frequent rains. That's correlation and causation, by the way, all due respect to amatbrewer.

 

[Shibui]

Most tap water has been pH-adjusted in order to protect the equipment used to pump and transport it. Ours where I am runs about 8.2. Most (but not all) plants don't like alkaline pH. If you experience two weeks or more without rain, your trees will suffer as the buffering capacity of the soil is overcome. What you want is good old rain. The pH will tend to be slightly acidic, and that's how God intended it. Your trees will definitely improve if you get frequent rains. That's correlation and causation, by the way, all due respect to amatbrewer.

But does not explain the difference between growth observed using rainwater from tank storage and rainwater direct from the sky or are you suggesting that rainwater stored in a tank changes pH to become alkaline?

BTW: our local water supply authority lists the pH requirement for treated drinking water as: aesthetic standard requires pH is between 6.5 and 8.5 units. Just checked the published results for last year. Treated town water in my area is mostly closer to 7 with min readings around 6.9 through to high results of 7.5 or 8 though upper catchments seem to have results from min 7 through to high readings up to 9.

 

[Zach Smith]

But does not explain the difference between growth observed using rainwater from tank storage and rainwater direct from the sky or are you suggesting that rainwater stored in a tank changes pH to become alkaline?

BTW: our local water supply authority lists the pH requirement for treated drinking water as: aesthetic standard requires pH is between 6.5 and 8.5 units. Just checked the published results for last year. Treated town water in my area is mostly closer to 7 with min readings around 6.9 through to high results of 7.5 or 8 though upper catchments seem to have results from min 7 through to high readings up to 9.

I was responding to Joe's original post where he was writing about the difference between tap water and rain water. Not sure where you got the stored rainwater vs falling rainwater piece, but that wasn't my point. If your tap water is closer to 7 pH, then your trees should suffer less pH-related stress from watering with tap water.

 

[Shibui]

My point is that changing from tapwater to stored rainwater probably won't give the results seen from rainfall. Example of rainfall V stored rain water illustrates that. It is not the rainwateras such, more the fact that it fell fresh from the sky that makes such a big difference. I believe that Joe's original premise - trees grow better after rainfall therefore water with rainwater will increase growth is exactly what Amatbrewer pointed out - false conclusion drawn from 2 facts. Correlation does not imply causation.

I do not have to contend with alkaline tap water so have no experience whether rainwater will produce better growth than the alkaline tap water. Maybe there will be some difference but unlikely to be the same as he has observed with direct rainfall. To check this someone will need to set up some plants and water half of them with tap water and half with stored rainwater and record the difference in growth. To be really valid the experiment should probably be double blind so unconscious bias cannot interfere with the results.

 

[penumbra]

Rainwater, like distilled water, becomes more acid as it is stored as it absorbs gasses , particularly co2.

 

[Velodog2]

Another way to look at this is to ask if the water typically used to water with (assuming it’s NOT rainwater) is impeding growth in some manner. I only water with collected rainwater due to the exceedingly high alkalinity (not the same as being alkaline, look it up) of my well water, which is very bad for plants and caused me excessive losses for years until I sorted it out. That revelation happened as a result of an extended drought when I watered with only well water for a long period of time. I almost quit the hobby as a result of the losses that resulted in.

 

[peterbone]

My understanding is that rainwater contains Hydrogen Peroxide H2O2. The rain collects additional oxygen atoms as it falls through the ozone O3. Hydrogen Peroxide is commonly used in houseplant fertilisers. It quickly breaks down in sunlight, which is why it's kept in brown bottles and why you should store collected rain water in the dark. Eventually that extra oxygen atom separates from the water in the soil and supplies oxygen to the roots. Tap water doesn't contain it because it's been exposed to sunlight for too long.

By the way, that smell you get when it starts raining after a dry period is partly ozone gases being released back into the air when the rain hits the warm ground.

 

[penumbra]

OK, after a quick google search I found that rain indeed does contain 3 form s of nitrogen which has been measured and does indeed contribute to plant health and growth in general. The post about Hydrogen Peroxide intrigues me because I know it has a benificial effect on plants but a quick search shows this is very minimal and in the 1 to 160 ppb range only occasionally being higher than 1 ppm. Also found that storms decrease the amount of H2O2 but increase the amount of Nitrogen.
This is a great subject and I am anxious to hear more.

 

[Lazylightningny]

I have also noticed better growth after rain water, and always assumed it was the extra nitrogen in the water as it passes through the atmosphere.

 

[BonsaiMatt]

Probably mostly due to a lower pH compared to tap water, and the added N (depending on location).
The N in rain varies a lot with location, because the sources of N being deposited are dominated by pollution (fossil fuel emissions and fertilizers), not N2 (atmospheric nitrogen). So not everyone would see the same increase in N due to rain. Just something to think about...
I don't think effects from hydrogen peroxide would be noticeable.