How Soil pH Affects Plants

Plants will grow best when pH conditions of their soil are close to neutral and just a touch toward more acidic. Extremely high or low in either direction (acidic or alkaline) and plants won’t do well.

Simple explanation of pH

On the scale from 0 to 14 with 0 being most acidic and 14 most alkaline, 7 is neutral. It is a logarithmic scale where each increment is times 10 — meaning if your soil pH level is 5 it’s ten times more acidic than soil with a pH level of 6 and 100 times more acidic than soil with a pH of 7.

Test the pH of your soil

There are pH meters available in garden centres or online that may be used to easily and quickly test the pH of your soil; be sure the your test sample is moist or you won’t see a reading. The other option is to take a soil sample to a lab, but the home method seems a more satisfying method to me, and young scientific minds that may be around when I take the test are usually fascinated by any activity involving test samples!

What makes the soil Acidic or Alkaline?

Original material such as the ground rock will dictate whether the soil is acidic or basic for example:

  • limestone will create a more alkaline soil
  • silica in the original rock will cause the soil to be more acidic.
  • Fertilizers containing ammonium urea will cause the soil to be more acidic.
  • Rainfall will add calcium and magnesium to soil causing higher acidity but in drier areas the soil will be more alkaline.

Increasing the Acidity or Alkalinity of Soil

Depending on the plants you’d like to grow you may want to bump up or bump down its pH levels.

To increase the soil’s pH level or make it more alkaline, you can add lime in the form of ground agriculture limestone, hydrated lime or burnt lime. Fine particles added to the soil will work more quickly to increase the pH, they will dissolve faster, permeating the soils and lowering the acidity. The process of neutralizing will take sixty to ninety days.

To decrease the pH levels or make the soil more acidic, add sulphur or aluminum sulphate. Aluminum sulphate will dissolve quickly and increase soil’s acidity upon dissolving but it’s extremely easy to over-do and the effect of the aluminum sulphate will be short lived. A slower but more commonly recommended way is to use sulphur; soil bacteria in conjunction with the sulphur will work to increase the pH of soil but like the process of decreasing pH, it is slow.

So, depending on whether you want to adjust your soil or work with it the way it is, here are a couple of plant lists and their soil preference.

Plants that Tolerate more Acidic Soil

Trees

  • Fir (Abies)
  • Spruce (Picea)
  • Pines (Pinus)
  • Upright Yew (Taxus)
  • Hemlock (Tsuga Canadensis)
  • Horse Chestnut (Aesculus)
  • Birch Betula
  • Buckeye (Aesculus)
  • Alder (Alnus)
  • Oaks (Quercus)
  • Pin Oak (Quercus palustris)
  • Mountain Ash (Sorbus)
  • Magnolia (Magnolia)
  • Serviceberry (Amelanchier)
  • Larch (Tamarack) Larix
  • Fringetree (Chionanthus)
  • Pagoda Dogwood (Cornus)

Shrubs

  • Junipers (Juniperus)
  • False Cypress (Chamaecyparis)
  • Dwarf Hemlocks (Tsuga)
  • Yews (Taxus)
  • Dwarf Spruce (Picea)
  • Mugho Pine (Pinus mugo)
  • Sweetbush (Clethra)
  • Dogwood (Cornus)
  • Winterberry (Ilex verticillata)
  • Mountain Laurel (Kalmia)
  • Azalea
  • Rhododendron
  • Serviceberry (Amelanchier)
  • Hydrangea (Hydrangea macrophylla)
  • Bog Rosemary (Andromeda)
  • Blueberries (Vaccinium)

Perennials

  • Lupines (Lupinus)
  • Butterfly Weed (Aesclepias)
  • Turtlehead (Chelone)
  • Snakeroot (Cimicifuga)
  • Fringed Bleeding Heart (Dicentra)
  • Foxglove (Digitalis)
  • Gentian (Gentiana)
  • Primroses (Primula)
  • Trillium (Trillium)
  • Woodland Phlox (Phlox stolon)
  • Virginia Bluebells (Mertensia)
  • Coral Bells (Heuchera)
  • Barrenwort (Epimedium)
  • Marsh Marigold (Caltha)
  • Lady Slipper (Cypripedium)
  • Hardy Fern-most varieties

Groundcovers

  • Winterberry (Cornus Canadensis)
  • Wintergreen (Gaultheria)
  • Lilies of the Valley (Convollaria)
  • Bearberry (Arctostaphylos)

Misc

  • Wax Begonias
  • Calla Lilies
  • Narcissus
  • Potatoes

Plants that Indicate Soil Might be Acidic

  • Dandelions
  • Wild Strawberries
  • Ox Eye Daisies
  • Red Cedar
  • Dock (Rabbit Tobacco)
  • Cinquefoil
  • Plantain

Plants that Indicate Soil Might be Alkaline

  • Chickweed
  • Spotted Spurge
  • Queen Anne’s Lace
  • Goosefoot
  • Chicory

Plants that Tolerate More Alkaline Soil

  • Boxelder (Acer negundo)
  • Japanese Barberry (Berberis)
  • Hackberry (Celtis)
  • Russian Olive (Eleagnus)
  • Sargent Crabapple (Malus)
  • Mockorange (Philadelphus)
  • Locusts (Robinia)
  • Bridalwreath (Spirea ‘Van Houtii’)
  • Arrowwood Viburnum (Viburnum)

Source: plant lists for acidic and alkaline soils from bachmans.com

5 Comments

  1. Jeffrey Smith

    Thanks for the advice, and your website really looks outstanding. Exactly what wordpress theme are you utilizing?

  2. Patricia Timmermans (Post author)

    Hi Jeffrey, thanks for visiting! The wordpress theme I’m using is Billions 1.1.4 by Turbo Tax

    Have a great week 🙂

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