I have never understood soil acidity for bonsai, so thought I would start a thread so I and others could learn. I understand the conifers require more acidity than deciduous trees. Maybe some trees require more than others. So what is an acceptable acidity level for conifers and for deciduous trees AND how do you measure that level with soils? I can measure the acidity level of my water but not sure about measuring the acidity of soils. Maybe the acidity level of water determines the same with soils. Is there a chart or something that shows the acidity level needed for the best health with various trees? Help and knowledge appreciated. Thank you.
Soil acidity
- Thread starter August44
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Drop Branch Murphy
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As a long time bonsai hobbyist who understands college level chemistry but doesn't utilize it too much when growing plants, here are a few things that pop into my mind concerning your question.
The availability of certain nutrients is affected by soil acidity. With that being said, I have no idea what my actual soil acidity is. I use primarily an Akadama-Pumice-Lava mix for my refined trees and a "grow" mix of bark/turface/spent bonsai soil and any other used aggregate I have available for anything being grown out in nursery cans. I've essentially used the same mixes for 1 decade in MA, 12 + years in GA, and now for a year + in MI. My water quality has changed but my soil mix hasn't. I've fertilized the same way in all three locales as well. Ultimately, I'm of the belief that if you have what's considered good water and you're not using an exotic soil mix, you shouldn't worry about it. All bets are off if you've got crappy water like much of the western USA.
I've actually considered certain conifers to do well in an alkaline environment as opposed to acidic... but I suspect it's more of a tolerance then a preference. Many tree species perform equally well in the same range of soil acidity, which would typically fluctuate between slightly acidic and slightly alkaline. A 7 ph is neutral, so a smidge on the acidic or alkaline side shouldn't affect plant health regardless of species, except for the most sensitive.
Your soil components will determine soil acidity, but your water quality/composition and frequency of fertilization will be the ultimate determining factor in how acidic or alkaline your soil becomes over time.
@Leo in N E Illinois is the bomb when it comes to the science behind good and bad horticulture... hopefully he'll chime in and, if I'm blatantly wrong in anything I've stated above, let me down gently
The availability of certain nutrients is affected by soil acidity. With that being said, I have no idea what my actual soil acidity is. I use primarily an Akadama-Pumice-Lava mix for my refined trees and a "grow" mix of bark/turface/spent bonsai soil and any other used aggregate I have available for anything being grown out in nursery cans. I've essentially used the same mixes for 1 decade in MA, 12 + years in GA, and now for a year + in MI. My water quality has changed but my soil mix hasn't. I've fertilized the same way in all three locales as well. Ultimately, I'm of the belief that if you have what's considered good water and you're not using an exotic soil mix, you shouldn't worry about it. All bets are off if you've got crappy water like much of the western USA.
I've actually considered certain conifers to do well in an alkaline environment as opposed to acidic... but I suspect it's more of a tolerance then a preference. Many tree species perform equally well in the same range of soil acidity, which would typically fluctuate between slightly acidic and slightly alkaline. A 7 ph is neutral, so a smidge on the acidic or alkaline side shouldn't affect plant health regardless of species, except for the most sensitive.
Your soil components will determine soil acidity, but your water quality/composition and frequency of fertilization will be the ultimate determining factor in how acidic or alkaline your soil becomes over time.
@Leo in N E Illinois is the bomb when it comes to the science behind good and bad horticulture... hopefully he'll chime in and, if I'm blatantly wrong in anything I've stated above, let me down gently
Glaucus
Omono
Solubility of minerals changed at different pH values. Plants need minerals from the soil to combine with the carbon from the air and light from the sun.
However, too much or too little of something is debilitating or even toxic. Therefore, different species are good in taking up different minerals. Namely, the ones that are less soluble in the type of soils they evolved to live in.
Which means if the plant is grown in a soil with a different pH, they may be deficient in some of these minerals.
A quick google search gives me this site with a table of species and pH preference:
www.almanac.com
Can't stand in for the accuracy of that website, though.
However, too much or too little of something is debilitating or even toxic. Therefore, different species are good in taking up different minerals. Namely, the ones that are less soluble in the type of soils they evolved to live in.
Which means if the plant is grown in a soil with a different pH, they may be deficient in some of these minerals.
A quick google search gives me this site with a table of species and pH preference:
Soil pH Levels for Plants
This chart shows optimum soil pH levels for a variety of trees, shrubs, and flowers. From The Old Farmer's Almanac.
Can't stand in for the accuracy of that website, though.
I just measured the Ph of my water using a device that measures the Ph in aquariums. It showed my tap water to be 7.2
WNC Bonsai
Masterpiece
Here is a figure showing the ideal pH range for a wide range of plants. However many forest species grow in acidic soil due to the natural formation of organic acids when plant matter decomposes. Some plants like azaleas, rhododendrons, blueberries do need more acidity than others. There has been a lot of discussion on various forums as well as in YouTube videos on how to treat household water that is basic. As you can see from the figure if your water is representative of the soil acidity then your plants may show signs of iron and other trace metal deficiencies. Anyway here is the figure.
Leo in N E Illinois
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@August44 - Hi Peter, the topic of pH is "twisty" especially as you move away from liquids. The official way to measure soil pH is to take a soil sample, put it in a glass container, add just enough water to saturate to soil surface. Allow to stand for one hour, pour a little water into a beaker and check the pH. That's your soil pH.
The chart @Cofga posted shows that the nutrition we are worried about for trees is all nicely available between 6.2 and 7.3, if your test gives you numbers in this range, don't worry.
You've been growing nice trees for a while, unless you are seeing a new problem, I would not be worrying about pH of your soil or your water. Both have been good so far.
Only if you add a unique sensitive species like carnivorous plants, you should be good.
The chart @Cofga posted shows that the nutrition we are worried about for trees is all nicely available between 6.2 and 7.3, if your test gives you numbers in this range, don't worry.
You've been growing nice trees for a while, unless you are seeing a new problem, I would not be worrying about pH of your soil or your water. Both have been good so far.
Only if you add a unique sensitive species like carnivorous plants, you should be good.
Thank you Leo! Always nice to have you chime in.
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