Overwatering in colanders

So; mourning the demise of yet another little tree in a pot, I began to wonder. Is it possible to overwater a tree growing in a colander or strainer bottomed pot? Of course, the reason for my musing, “did I overwater or underwater?” was the catalyst for the question. I, honestly, could never tell if the shohin sized JBP was wet or dry. It seemed no matter what I did it never got really healthy. Truth be told, it’s been pining away (sorry) for a while now. But it’s in a plastic pot that has a grid for a bottom, which led me to the question. Any experiences or thoughts shared will, of course, be greatly appreciated.

The answer is yes! The soil or aggregate that you have the pine growing can hold excessive water even if the drainage is good. Loam or clay or compost can all stay very moist.
Pines like to dry out in between watering.
If you use pumice or lava rock the drainage is better, but they still like to dry out before watering. I use the weight of the container to tell me if it has dried enough. My pines have suffered from overwatering and I have learned the hard way to check them before watering on a schedule. :thinking:


What would have been the signs of the overwatering in the tree?

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I just read the chapter on water quality in Michael Hagedorn’s Bonsai Heresy and he talks about the decline of his trees due to changing water quality with the season. What is the pH and hardness of your water? That can have a big impact on the tree’s health. One of the reasons that Mirai is where it is located is the water pH is 6.5 which is just about optimal. My water is nominally pH 8 so I use acid to reduce it into the 6.5 - 7.0 range and the response from the trees is very good.


Hi @MartyWeiser, what sort of acid do you use or doesn’t it make a difference? My water is also high as yours though sometimes it’s as high as 8.5. I generally don’t have a problem in a normal year when we get at least average rainfall. However during May we only got 6% of our average monthly rain so it meant using lots of tap water, which coupled with unseasonally high temperatures meant a few of the trees struggled.
How much acid do you add ?


I use phosphoric acid in a product called pH Down that is designed for the hydroponics folks. It is 55% P2O5 and so it would be 0-55-0 fertilizer. I got a pH test kit from the same store and did some experimentation. For my indoor plants I mix 2 mil of the pH Down in one US gallon of water which gives a pH of 4. I then dilute that 20:1 into the watering can.

For my outdoor trees I made a stronger solution that gets diluted into a 5 gallon bucket that is ten sucked into the hose when watering using a Mazzei in-line siphon injector. That system takes a little adjustment to get the right mix.

There was a discussion a while back about having too much phosphorous in the system tying up the iron. I make sure to include some iron in my fertilizer and have not had any issues. The person who pointed that out, suggested acetic acid (vinegar) which is also a weak acid from a chemistry standpoint like phosphoric, but I have not tried that. Michael Hagedorn suggests muratic acid (HCl) in his new Bonsai Heresy book since it is easy to get, but I am not sure about introducing more chlorine. I also though about nitric acid since it would introduce the nitrate ion, but it is harder to obtain and is fairly hard fairly dangerous. Of course all of the acids I have listed dangerous in any concentrated form.

A side note is that concentrated phosphoric acid is used in the beer and similar industries to both clean equipment (it dissolved biofilms quite well) and to adjust water pH.


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Thanks Marty.
Lots of food for thought there. I like the idea of using vinegar as it’s something that’s pretty much available all the time.
My water butt (I don’t know what you call them) was virtually empty, plus the water wasn’t exactly nice. With rain forecast I ditched the water and scrubbed it clean. 24 hrs later and it is brim full. 300ltrs to be precise. So the immediate panic is delayed…until next time.
I only use it on azaleas and such as hinoki, hornbeams, trees that can’t handle high ph. So it’s good to know an alternative that will tide me over a bit. Cheers…

I find the soil to be heavy and wet when I water too frequently. Always check before I water is my goal to keep the trees healthy and thriving. :thinking:
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Thanks for the link. That is helpful.

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Thanks for the replies. Bob; I use a mix of 1:1:1 acadama, lava, pumice; 1/4 - 1/8 “, sifted and rinsed till clear after potting. My house water pH is as yours, Marty, about 8 and I had used acid to lower the pH to <7.0 but recently watched a new beginner video in which Ryan says pH isn’t that important which
lead me to venture forth and use the harder water. Surprisingly, my Jap. Maples are doing fine without any signs of chlorosis this far. I do intend to go back to acidic water for a while to rinse out any accumulated calcium salts.

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