Last summer, I wrote two posts about the connection between water pH and bonsai health (see “Effect of fertilizer on pH” and “How to lower pH” for details). In light of the recent high temperatures across much of the U.S., I thought now would be a good time for a watering update.
I started using a Dosatron chemical injector (model D14MZ2) last year to acidify the water I use for bonsai. For a few months I used pH Down to acidify the water, but after a while I noticed that the pine foliage took on a subtle blue hue. The trees were otherwise healthy, but I didn’t find the color natural so I tried something else.
The next concentrate I used was a weak solution of Dyna-Gro Foliage-Pro. Using watered-down fertilizer isn’t a recommended approach for acidifying water – or anything else that I know of – but I was curious to see the effect it would have on the trees.
This too gave pines a bluish hue so I went back to using untreated water (pH 9.0 or higher) for two months to establish a baseline.
Within days the pines turned yellow so I knew the fertilizer was responsible for keeping them (bluish) green up to that point.
The next concentrate I tried is acetic acid – the main component, other than water, in vinegar. Here’s how I use it.
I add 3/8 cup of 30% acetic acid to 5 gallons of water to create a concentrate. The Dosatron injects the concentrate at a ratio of 1:100 into the water I use in the garden. This brings the pH of the water far below the pH 9.3 that’s been coming from the spigot this summer.
Treated water at pH 6.4
This approach worked well in winter before I started fertilizing my bonsai. When it was time to start fertilizing, I mixed up a concentrate with Dyna-Gro Foliage-Pro (full strength) and prepared to use it on all of the trees in the garden.
As soon as I had everything mixed up, I realized that I didn’t want to start fertilizing my mature deciduous bonsai, so I used the Dyna-Gro concentrate for some trees and the vinegar concentrate for the rest.
Not wanting the pines to turn blue again, I made a third concentrate with fish emulsion. Emptying the emulsion into a receptacle was simple enough, but the liquid was too viscous to run through the Dosatron’s filter.
To thin out the fertilizer, I add 1.5 gallons water to 1 gallon of fish emulsion and mix them together. This mixture is thin enough to run through the filter which allows me to apply it with the Dosatron.
Simple, right?
Dosatron chemical injector with three concentrates at the ready
Wrong. What I quickly found is that I was spending a lot of time switching between receptacles, waiting for each new concentrate to run through 75′ of hose, and then testing the result to make sure it the pH was within the target range of 6.0-6.5.
The problem is that different trees have different fertilizer needs throughout the year. Using a solid fertilizer like cottonseed meal or homemade cakes (aka “dango”) makes the problem go away, but since animals continue to steal any solid fertilizers I use, I’m limited to using liquid fertilizers.
I’m starting to feel more comfortable with the above approach, but I can’t recommend it without hesitation.
After twelve months of this approach, the key takeaways from a practical standpoint are:
- Chemical injectors are great when all of the trees in the garden have the same water or fertilizer needs
- Solid fertilizers are great when different trees have different fertilizer needs
- Using multiple concentrates is great when you don’t need to switch between them too much (or if you have one spigot per concentrate)
Now for the most important question: does acidifying the water work?
In short, yes, but with a caveat. I have yet to test acidified water against non-acidified water in a side-by-side comparison – that’s more complexity than I’m set up to manage these days! That said, I’ve used far less fertilizer this year than I have in past years and I’m seeing similar results in terms of the bud size, needle length, and the color I’m seeing in the foliage.
Green foliage on Black pines
Where does this leave us? Maybe with the familiar lesson that there’s no simple solution to keeping bonsai healthy.
Have any questions – or tips – about watering and fertilizing the bonsai in your garden? Feel free to share them in the comments below!
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Edward Stanton says
Jonas, reading about your heroic efforts to balance pH made me think, “Wouldn’t a rain barrel be easier?” But then I remembered you probably don’t get enough rain in Alameda.
My question has to do with the plastic bottles pictured in the middle (second) photo. As someone who does live in a region with abundant rain (about 55” per year), I use a 50-gallon rain barrel and seldom have to supplement with tap water (about 7.5 pH here), which I let sit for at least 24 hours to leach out some of the chemicals before using. I transfer the rainwater from the barrel to the best, hardest plastic juice or water bottles I can find. Somewhere in his Bonsai Techniques I or II, John Naka mentions the danger of the plastic bottles deteriorating and contaminating water. One of my bonsai teachers told me not to worry about this, since the quality of plastic bottles has probably improved since Naka’s time. What do you think, and what kind of bottles do you use? Thanks as always!
Jonas Dupuich says
Ha – a rain barrel would be much easier if we had more rain (and I had fewer trees)! We normally don’t get any rain from June through September. As for the plastic, I have no idea if there are any harmful compounds that can leach into the water. I’d have to do some research to see if that’s an issue with more up to date materials.
The bottles in the photo are empty fertilizer containers from Dyna-Gro. They have lids an handles and they are very strong which makes them a convenient option.
Edward Stanton says
Hello again Jonas, thanks for the quick and helpful reply. Please do let me know if you find out anything relevant about plastic containers.
Jane Hall says
Hello Jonas…
I really enjoyed reading your article on trying to reduce the ph of your bonsai water. My husband and I faced this dilemma years ago finding that our well water was not only in a very high ph range , but also was high in calcareous salts. After considering the difficulties of water purification and dosing….the upkeep and expense of equipment that required, we turned to rainwater. Being an avid aquarium keeper for years I had tested our rainwater and knew it to be fairly acidic here in northern Louisiana. So we began collecting rainwater, storing it in large plastic garbage cans, and hand watering. Within a few short months we saw the improvement in our trees…and importantly, the ability to now grow acid loving and salt intolerant trees like Satsuki azaleas, junipers…and our favorites, Japanese maples. It is labor intensive here in the summers, but it does bring us closer to our trees! Our catch basins from our roof gutters are emptied into large buckets for immediate watering. These often grow algae (mosquitoes are easily controlled with Mosquito Dunks…biologically safe for even the tiny tree frog tadpoles that sometimes hatch), which acts like a mild fertilizer as we water. All in all our trees are much happier and healthier for the rainwater!
Jonas Dupuich says
Thanks for the note Jane, what a great success story! Rainwater is frequently a great option for our trees, and, as you noted, there are benefits to becoming more involved with our water sources. Best of all, it’s great to hear that you can now grow species you appreciate like maples, junipers, and azaleas. Thanks for sharing!
Paul Dominic says
Hi!! Jonas – Thank you , as someone who watched his favorite birch tree leaves turn yellow and dry up this article has great information.
Question : is there an easier / poor man’s way to lower PH besides equipment like Dosatron ? are occasional treatments helpful (say once a week) ?
I don’t have nearly as many trees as you of course 🙂
Was able to save the birch after some last minute acidic fertilizer.
Jonas Dupuich says
Hi Paul! The easiest fix is to use organic fertilizer on the surface of the soil. The fertilizer will lower the pH a bit as the water runs through it. If you use a watering can, you can add a few drops of vinegar (test the actual amount) every time you water. If you use a hose to water, you can try a Hozon Siphon mixer.
Although I haven’t tested it, I’ve read that trees don’t love variable water pH so I wouldn’t try the once-a-week approach.
Michael Jensen-Akula says
Hi Jonas
love to see the thinking here. I have a fairly large pond in the back yard with a small pump/waterfall. I ‘reverse’ the pump and have a hose set-up that, such that i can water with the pond water (pH about 7 with the obligate fish and turtle poop as my nitrogen source). I do notice that i get a few (and occ more than a few) more weeds in my plants when i water this way compared to when i use the regular hose. I top off the pond every couple of days. I don’t use a liquid dechlorinator if adding small amounts of water to the pond and the fish don’t seem to mind.
Jonas Dupuich says
Hi Michael – that sounds like a great and natural way to improve the water for your trees! As long as there aren’t too many weeds, it sounds like you’ve found an efficient approach to improving the water for your trees.
Allan says
Excellent post on a potentially complex subject! The induced blue color is an interesting result, seemingly from the increased availability of nutrients from the pH Down (phosphorus?) and other fertilizers? I would love to see an expanded discussion on the other attributes of your tap water such as alkalinity, hardness, and content of calcium/magnesium and how they impact an acidification or fertilization regime. But perhaps that level of chemistry nerdiness is better suited for your forum. As you know, the general water quality reports for your area list a high pH, but relativity low alkalinity and low hardness (soft water). Your water’s low buffering capacity (ability to resist change in pH) combined with high pH seems to be the less prevalent condition across the US where groundwater or surface water is in contact with calcium-bearing sedimentary rocks. The acidification of your water further lowers the already low alkalinity perhaps to an undesirable level. I’d be interested to know if you supplement calcium and magnesium in addition to your normal fertilizer procedure. Thank you for the great blog!
Jonas Dupuich says
Thanks Allan! I too am curious about the discoloration and am assuming it relates to the available phosphorus, but I haven’t tested this by adding high phosphorus fertilizer and seeing what happens. It could be that the exact mechanisms are more complex.
Great points about the overall water picture. My alkalinity is low (https://www.ebmud.com/water/about-your-water/water-quality/water-quality-report-english/#) so the pH adjustment requires very little acid. I haven’t supplemented the trees with calcium and magnesium but it’d be interesting to see if it makes a difference!
I have a couple more tests to complete which I’ll report back on soon in an upcoming post. I’m always willing to entertain water chemistry nerdiness but I rely on the water chemistry nerds for the information!
DAVID DEGROOT says
Regarding fish emulsion, I’ve found it less problematic if I strain it through a paint strainer before diluting it. You can get the strainers to fit various size containers. I use a 5 gallon bucket of concentrate with a Siphonex, so I use the size strainer that fits a 5 gallon bucket. I don’t know if this will work with a Dosatron, but if you like fish emulsion it might be worth a try.
Jonas Dupuich says
Thanks, David! I have filters that are either too big or too small – will have to look for paint strainers. The fish emulsion I use is so gloopy I need to thin it before straining it, but straining is great for removing the larger particles that regularly clog up the siphon filter.
Terri Wall says
Hi Jonas
The easiest way I have found to give my pines more acid (in addition to organic fertilizer-I use Biogold) is to use old coffee pods I have run through once for my morning cup, Regular roast not decaf or flavored coffee, I take one or two,(or three) depending on the size of the pot, and I cut slits in the plastic top (The side that gets punctured in the Keurig et al) , and turn the pod(s) upside down on the soil. Every time I water or when it rains some of the acid from the coffee grounds leaches into the soil. I also use them on my junipers in the same way. I don’t know how much I am helping the trees but have never seen an ill effect and I have been doing this for many years. They are, however, perfectly GREEN. I put them on in the Spring and take them off in the Fall before I put them away for the Winter.
Jonas Dupuich says
Hi Terri! I’ve heard of similar results from people using coffee grinds on the surface of the soil – I love that it’s such a simple and inexpensive approach. It’s a good argument for me to start drinking coffee!
Have you set a control where you don’t don’t use coffee with several trees and confirmed that they turn yellow?
Todd Morgan says
Jonas, I tried using lemon juice, and then vinegar, just adding it to a 5 gal bucket, to get around 6.0 to 6.5…. But if I wait and let it sit until the next day, it changes back to around 8 or so. So then the question is, what is the pH in the pot?
when I would use pH Down, and it only goes back up a couple of decimal points by the next day… but it is such a lot of work, have just gone back to using cottonseed meal around the tree. and it seems to be ok. So thanks for confirmation that it is probably ok to do just that…
Jonas Dupuich says
Thanks for the note Todd! Many acids dissipate and lose effectiveness over time. That’s why using organic fertilizer is such a good approach – it’s a low-effort way to ensure a good environment for the roots. If you didn’t have problems with the cottonseed meal before, it’s likely a great way to improve the water and fertilize the tree at the same time!
Nathan Davila says
Jonas,
I was just catching up on reading some of your recent posts. I myself have been considering the installation of a water treatment system for my garden. I would like to know how you went about setting up your system. Any possibility that the set up could be covered in a future blog post?
Jonas Dupuich says
Good question Nathan – I might do that. I followed a standard bypass installation like the example here. The main reason I didn’t go into detail is that most of the pipes are below ground and I didn’t get photos of the installation so there isn’t much to show beyond what you can see here in the post (the water goes up on the left, runs through a filter, then passes through the injector and a check valve before returning to the line that runs into the hose).
The one recommendation I have is to do some sort of bypass approach as it lets you run water through the injector or bypass it entirely (possibly for maintenance) at any time.
If you have specific questions about your setup, feel free to post them to the forum: https://ask.bonsaitonight.com/