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.
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!
New Episode of the Bonsai Wire Podcast
This week’s bonus episode features a brief conversation with Andrew Robson in which we discuss using colanders for developing pre-bonsai.
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