How To Adjust Soil Ph Value

How to adjust the soil PH value

In one of my last posts I reported on the topic of nutrient deficiency in our plants and how to recognize it.

A very large influence on the nutrient uptake has here the soil PH value of the garden or plant soil. If this is not, in an optimal range for our plants, a nutrient uptake (minerals and trace elements) is only limited possible and it comes to the mentioned nutrient deficiency …

The common PH value range for most garden plants is between 5.5 and 7.5, although the range for optimal nutrient uptake differs from plant to plant. A small overview of the ideal PH value range of different plants can be found here.

How to determine the soil PH-value?

But not only our beloved plants, but also the creatures in the soil feel most comfortable at a PH value between 6 and 7.5.
In this article I do not want to report about the optimal soil PH values or why the PH value is so important for the plants, but rather show the possibilities how to lower or increase the soil PH value. To determine what PH value our soil has, an electronic soil tester is recommended.

The PH value of the soil tells us how acidic (lower than PH value 7) or alkaline (higher than PH value 7) a soil is. For comparison a soil with PH value of 7 is called neutral. How acidic or alkaline a soil is usually depends on its content of calcium. In acidic soils, the calcium content is usually very low, in contrast, the alkaline soil has too high calcium content. In a neutral soil (PH value 7) calcium is present in the ideal proportion, so that it can neutralize the acidity in the soil.

In order to change the PH value of the garden soil, the calcium content in the soil should be changed. In the case of acid soil (PH less than 7), since the soil lacks calcium, you can add lime, which contains calcium carbonate. This addition of calcium makes the soil more alkaline and the acidity of the soil is thus reduced for a period of about 5 years. Also adding basalt flour helps to increase the calcium content and thus the soil PH value and at the same time reduce the acidity of the soil.

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But please do not immediately think much helps much.
Because an overcalcification of the soil leads to the fact that the soil becomes too alkaline and that we do not want now….
We have just looked at how we can increase the PH value in an acidic soil. In an alkaline soil (PH value higher than 7), we can not simply remove the lime from the soil to lower the PH value 😉 .

Rather, appropriate substances are added to the alkaline soil to lower the PH value of the soil. Often mentioned here is the addition of sulfur, but sulfur acts very slowly.
Rather, if the PH value is to be lowered only in small areas, substances such as iron sulfate should be used here.

Ferrous sulfate reacts much faster than elemental sulfur. But also ammonia fertilizer helps to lower the PH value, it is important that the fertilizer does not contain calcium nitrate and potassium nitrate because these ingredients increase the soil PH value.

On the whole, it is quite easy to regulate the soil PH value. If you have determined the soil PH value and approach the adjustment of the PH value with care.
Finally, I will summarize the possibilities of lowering and increasing the PH value again to give a better overview of the individual possibilities.

Ways to increase the PH value of the soil (if the soil is too acidic):

  • Adding lime will increase the soil pH (150 grams of carbonic lime per square meter) to maintain the PH value if the soil is already too acidic accordingly more (see packaging).
  • Adding basalt flour (rule of thumb 10g per liter of soil increases the PH value by one unit)
  • Possibilities to lower the PH value of the soil (if the soil is too alkaline):
  • Introduction of granite flour
  • Adding coffee grounds (only useful for small areas)
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Application of ferrous sulfate (5 kilos of ferrous sulfate per 10 square meters – lower PH value by one unit)
Introduction of “acid” humus from chopped coniferous wood (highly recommended for large areas).
I hope that this small contribution on the subject of lowering or increasing the soil PH value has answered a few questions and helps you a little…

If you still have questions about this topic, just ask and I will try to answer them.

Optimal soil PH value for plants

Which soil PH value does which plant need?

In another article I have already reported about various trace elements and their deficiency symptoms.

With this post I would like to give you a small overview of the optimal PH soil value of some plants. Before we put the plants in the ground or in our planting pot, we should see if our planting soil has the necessary conditions. The quickest way to ensure this is to test the PH value of the soil. For this purpose, we recommend an electronic soil tester*, or who wants it cheaper PH-value test strips or tablets.

If we have now determined the PH-value of our soil and it is in the required PH-value range we can start planting. If the values are not yet optimal here a contribution (I will still write) about lowering or increasing the soil PH value.

But now back to the actual topic of the post, an overview of the optimal soil PH of different plants.

Overview optimal soil PH value:

Garden plants and potted plants

  • Blue-rain (5.5 to 6)
  • Begonia ( 5,5 to 6,5 )
  • Calla (4 to 6 )
  • Clematis ( 5,5 to 7 )
  • Cosmos (6.5 to 8 )
  • Dahlias ( 6 to 6.5 )
  • Forsythia ( 5,6 to 7,5 )
  • Fuchsia (6 to 6.5 )
  • Geraniums (5.5 to 6)
  • Gloriosa (6,5 to8 )
  • Hibiscus ( 5 to 6.3 )
  • Hydrangea ( 4 to 5.5 )
  • Hyacinth ( 6 to 7 )
  • Jasmine ( 4 to 6 )
  • Cape baskets ( 6 to 6.2 )
  • Lilies ( 5,5 to 7 )
  • snapdragons ( 8 to 9.5 )
  • magnolias (5.5 to 6.8)
  • male chaffinch ( 5 to 6 )
  • Narcissus ( 6 to 7 )
  • Oleander ( 5,5 to 7,8 )
  • Ornithogalum dubium ( 6 to 7 )
  • Rhododendron ( 4 to 5.5 )
  • Roses ( 6,5 to 7,5 )
  • Scabiosa ( 8 to 10 )
  • Tibouchina ( 5,5 to 6,2 )
  • Tulips (6.5 to 7 )
  • Verbena (5.5 to 6 )
  • Ornamental plants and perennials in general 5.5 to 6.5 )
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  • Elephant foot (5.5 to 6 )
  • Dragon tree ( 6 to 6.5 )
  • Ivy ( 6 to 6.5 )
  • Ficus ( 5,5 to 6,5 )
  • Golden leaf palm ( 5,5 to 6 )
  • Cacti ( 5.5 to 6.5 )
  • Climbing philodendron ( 4.5 to 5.5 )
  • Schefflera ( 5,5 to 6 )
  • Yucca ( 6 to 7 )
  • Indoor ferns ( 5 to 6.5 )
  • Small table about the ranges of PH values.
  • Acidic: from 4 to 6
  • Neutral: from 6,5 to 8
  • Alkaline: from 8.5 to 10

This list could be written ad infinitum, but I think I have considered the most important garden and houseplants. If I should have forgotten nevertheless the one or other plant, then you announce simply below in the comments and I will add the plant of course…

The PH values given in the brackets are of course only approximate, the plant will not immediately die if it is not in the optimal PH range. But to allow an optimal growth as well as an optimal absorption of the trace elements, the plant should be in this range of the soil PH values.

I wish you still a nice Friday afternoon….


  • James Jones

    Meet James Jones, a passionate gardening writer whose words bloom with the wisdom of an experienced horticulturist. With a deep-rooted love for all things green, James has dedicated his life to sharing the art and science of gardening with the world. James's words have found their way into countless publications, and his gardening insights have inspired a new generation of green thumbs. His commitment to sustainability and environmental stewardship shines through in every article he crafts.

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