How to Lower Soil pH for Acid-loving Plants
Many types of ornamental plants require acidic soil in order to access and absorb nutrients. This quick tutorial explains how I lower soil pH for my acid-loving plants.
In my last article here on The Renaissance Garden Guy, I described in some detail the plight of one of my beleaguered rhododendron bushes. This plant had been harassed by a nesting mole, partially devoured by malevolent voles, and subjected to repeated saturation by alkaline waste water (rhodies thrive in acidic soil). I made a command decision this past week to attempt some drastic rescue measures: I’m going to transplant it to a large pot. This decision provides the perfect opportunity for me to demonstrate my soil acidification process.
By getting a big pot of soil ready to house this poor little bush, I can start with a clean slate, in a manner of speaking, and show you, from start to finish, how to lower soil pH for acid-loving plants.
How to Lower Soil pH for Acid-loving Plants: The Set-Up
Unlike my soil amending activities out in the garden, the process of re-homing my forlorn little rhodie involved the use of a large pot, and a sufficient amount of organic raised bed garden soil to fill it. This situation provided the perfect starting point for a quick soil pH amending discussion. The pot I used was large, and accommodated nearly 1.5 cubic feet of organic garden soil. The soil itself was advertised as having a pH of 7.0. Neutral. Neither acidic or alkaline. Perfect for talking about amending pH.
In order to prep the soil in the pot for my acid-loving rhodie and show you how to do it at the same time, I rounded up two more items: my soil analysis meter and a bag of soil acidifying agent. By now, my subscribers and regular readers know about the particular goods I use. My soil analysis meter is a Luster Leaf Rapitest 4-way unit, and the pH lowering agent is Espoma Soil Acidifier. The techniques outlined in this little tutorial assume the use of these two products.
FYI:
Soil acidity or alkalinity is measured on a pH scale. pH, according to Wikipedia, “historically denoting ‘potential of hydrogen’ is a scale used to specify acidity or basicity… ” The range of the pH scale is 0 – 14, with 7.0 being neutral. Values below 7.0 are considered acidic, and values above 7.0 are considered alkaline, or basic.
How to Lower Soil pH for Acid-loving Plants: The Steps
Here’s what we do with our pot full of neutral soil in order to acidify it:
Step 1. Determine Existing pH Levels
I never entirely trust retailers’ or manufacturers’ claims as they pertain to their respective products. At least until I check ’em out. So right off the bat, let’s make sure that the soil we’re using is really pH neutral. Here’s how:
- Sift and crumble the top several inches of soil with your fingers. Do this with the soil in your pots or with the soil in the ground in your garden. This ensures a uniform and fine consistency of the actual portion of the soil you’ll be testing and eliminates chunks, rocks, or air pockets which could affect the reading you’ll be taking with your meter. Use your fingers so you know when the soil’s consistency is uniformly fine enough. This is the section of soil which will be coming into contact with the meter’s probe.
- Wet the soil to a muddy consistency. Pour distilled water into the soil that you’ll be testing so that it’s muddy down to a level of several inches below the surface. This will ensure that even the smallest particles of the soil to be tested come into complete and uniform contact with the meter’s probe. This is critical for getting an accurate reading from the meter.
- Prep the meter and stick it in the mud. The Luster Leaf Rapitest 4-way soil analysis meter uses extremely sensitive alloy probes to measure soil pH, nutrient levels, and moisture levels. It uses a light sensor to measure sunlight levels. The alloy probes are extremely sensitive and must be prepared and maintained properly in order to generate accurate readings. The first step in prepping the meter for use in measuring soil pH levels is to move the test selector lever to the pH testing (bottom) position. Next, wet the probes with running, distilled water (poured from a container is fine). Don’t submerge or immerse the probes in any liquid. Once you’ve run distilled water over the probes, use the manufacturer-provided cleaning pad to thoroughly polish the surface of the pH measuring probe. It’s the probe located all the way to the right when facing the front of the unit. Now, insert the meter into the muddy section of soil we just created. Insert it so the bottom of the unit’s case is touching the surface of the soil, and all of the probes are completely inserted into the muddy soil. Wait 60 seconds and take your reading. Finally, once you’ve gotten your soil’s pH level reading, remove the meter and rinse the probes with distilled water and let them dry before putting the meter away.
In this case, the retailer’s claims were correct. The photo on the right shows the exact reading I got from the meter. The soil actually had a neutral pH of 7.0, as advertised.
I bought this Luster Leaf Rapitest 4-way soil analysis meter in February of 2022 and have used it successfully time and time again since then to test for soil fertility and pH levels. It also measures sunlight and soil moisture levels. It’s fast, easy to use, convenient, and accurate. By using this device, I’ve been able to determine the necessity of appropriate fertilizer applications and pH amending to the soil of a large number of the plants in my garden. Order it here, directly from Amazon, by clicking the #advertisement link. Note that this unit doesn’t test for iron levels in soil. Also note that I really love this little meter!
Step 2. Acidify the Soil
It’s all downhill from here, baby. We’re going to take this soil from neutral to acidic with a really simple application of the super effective Espoma Soil Acidifier.
- Read and follow the manufacturer’s directions. The amount of soil acidifying product we’ll use varies with the application. We’ll use a different amount for a potted plant than we would for a plant growing in the ground. And the suggested amount for established plants is different than that of new plantings. Determine your own situation and do as Espoma suggests. We’re using a giant pot, in this case, so we’d normally stick (more or less) with Espoma’s suggestions for acidifying the soil for potted plants. I also know, however, how this stuff works and I’m comfortable with taking the occassional liberty with the manufacturer’s directions. I also know that the plant that’s going to be growing in this soil – my rhodie – requires a soil pH, optimally, of around 5.5. So here, we need to get the pH down fairly significantly. I’m going to be a bit more liberal with my application then Espoma suggests. Note: I’ve got experience using this product and I’m comfortable (and probably stupid) with modifying suggested application amounts. DON’T BE LIKE ME. FOLLOW ALL MANUFACTURER’S DIRECTIONS. YOUR HEALTH, AND THE HEALTH OF YOUR PLANTS, DEPEND UPON IT!!!
- Wear hand protection. We’re handling a product here that contains sulfur. Enough said. Glove up.
- Apply the product, work it into the soil, and water it in heavily. Again, follow Espoma’s directions for application. Apply it to the soil’s surface according to Espoma’s directions. If the soil you’re amending is in the ground in your garden, and there’s mulch over it, move the mulch out of your way before you apply the product. Since we’re dealing with a big pot of dirt in this example, and there’s no mulch in our way, we’ll apply it directly to the soil’s surface. Once that’s done, I like to work the product into the top inch or so of soil with my (gloved) fingers. Once that’s done, water the hell out of it. Watering activates the product and allows it to effectively permeate the target area and penetrate to depths where a given plant’s deep roots can access it.
- Wait a week and re-test. I like to wait about one week before I test the target soil, or amend it further with fertilizer. In a week’s time, particularly if there’s been rain or consistent watering, Espoma’s product will have time to effect a relevant drop in pH level. I recommend testing after this period of time. In the case of this tutorial, however, I re-tested the soil here less than 24 hours after I applied and watered in Espoma’s product. The photo below left shows the analysis meter’s reading of a neutral pH level of 7.0 when I first tested the soil (before the addition of soil acidifier). The photo below right shows a reading of about 6.8, taken less than 24 hours after the reading on the left. This illustrates the effectiveness of the Espoma product. In another week, the pH level should be significantly lower than even the shown level of 6.8. The soil is definitely acidifying, thereby becoming hospitable to the soon-to-be-transplanted rhodie. This plant will be able to access and utilize any fertilizing product I choose to add to this soil. Good deal.
For a more detailed discussion on both the chemistry and the expected time frame(s) involved with the soil acidification process, you can glimpse into the future and read my article of 12-23-23, “Aciidifying Soil in Winter in the Midwest.”
Espoma Organic Soil Acidifier is the perfect product for lowering the pH and increasing the acidity of your garden’s soil. It’s a fabulous organic product which I’ve used to lower soil pH for plants like my blue hydrangeas and my rhododendrons, azalea, and pieris. It’s very effective and allows acid-loving plants like these to properly access and utilize nutrients from fertilizing products. Order it here, from Amazon, by clicking the #advertisement link.
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Knowing how to lower soil pH for acid-loving plants also means knowing when to do it. The three pics below show my rhodies and pieris getting the acid treatment in winter. In my garden, the acidification process is a year-round endeavor.
So now you’ve got my soil acidifying process, and the products I use to implement it, in a nutshell. Or rather, in a flower pot. This “controlled” example was a good one because we were able to easily focus just on the process and the products. There weren’t any extraneous factors in play as is generally the case when amending soil pH in the ground in a garden. But, although it’s taken place in the controlled microcosm of a large flower pot, this little tutorial should still provide you with enough info to extrapolate and to acidify soil in your garden, or in any other location you’ve got in mind. The process is, after all, still essentially the process, and the tools to implement that process are just as effective in the sometimes ferocious environs of a home garden as they are in a big old flower pot.
Cheers, and Happy Gardening!
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Ok, one clematis done, not so much a Matrix more like, Oh what a tangled web we weave! Other jobs: My pH is 7 so off to acidify, thanks Doc!
I hope you’ll share pictures of your clematis. I’m sure it’s beautiful, Jill. Don’t go to crazy with the acidifier. Slightly acidic is just fine. I’m looking forward to seeing those vines of yours – thanks, Jill!
Great article ! Your rhodie is going to be okay. All the love and care that you are giving it is going to pay off. Gardening is really a labor of love.
Thanks for the vote of confidence, Kevin. If it doesn’t pull through, it won’t be for my lack of trying. I’m definitely pulling out all the stops to save it. Glad you liked the article. Making life better for my plants, and easy for me, is always the goal here. Thanks again!
Great article. This is just what I needed to work on .
Thank you – glad you liked it! It’s pretty straightforward stuff. The Espoma product goes a long way and is incredibly effective, and the soil analysis meter is a snap to use. This system has been effective in keeping soil pH in the acceptable range for the acid-lovers in our garden.
Another amazing article!!!!
Watching your garden grow so beautifully every day tells me how awesome your skills are ❤️🌸
Well thank you so very kindly, Roxxy – I sure appreciate that! I really do my best to make my plants happy, while at the same time, trying to not kill myself with too much work. Soil pH is super important, and I tried to relay the most effective, quickest, and easiest way to make the ground more hospitable to acid-craving plants. I’m so glad you liked the article. Thanks again!
100% agree!!
Yes! Fully agree!
Thank you, B! Glad you like the info. It’s a pretty good system that’s worked well for me, and it’s pretty simple. Thanks again for the great comment!
You did good. It is nice to watch your garden grow.
Many thanks, Everly. I appreciate that. I’m up for trying, implementing, and recommending anything that makes life in the garden easier – for plants and humans, alike. As always, Everly, I truly do appreciate your interest, kindness, and encouragement.
Another informative article. Thank you.
Thank you, Nykki. I’m glad you found some decent info there. I try to provide info and product recs which have proven useful and helpful to me. Sometimes a little bit of passed-along knowledge is all someone needs to score a minor success in the garden. Thanks again for your kind comment.
Well, like I have said. You can always learn something new. I have never tested my garden soil. My dad had a agent that can out to our farm. I was very young but I think he tested the soil. Great information, thank you.
Thank you, Sharon. I’ve been hearing more and more about gardeners and farmers retaining independent companies to provide soil testing services. For farming operations and large/public gardens, that would make sense. For my purposes, the process I outlined here works perfectly. As always, thank you for your interest and your great comments.