A presentation by Ampol Orrungroj on February 10, 2019

Soils pH is defined as the acidity or alkalinity of the soil.  The pH scale is from 1 to 14, where 7 is neutral.  Anything below 7 is acidic and anything over 7 is alkaline.  Generally soils in the eastern part of the United State are acidic, whereas soils in the western states are alkaline.

The correct pH level in our garden soils make a huge difference to the health of our plants, with most plants growing best in slightly acidic to neutral soils (pH between 6 and 7).  Our San Diego garden soils may have high salinity from our irrigation water.  To correct high salts, we need to apply enough water to leach away excess salts from the root zone.

Mother Nature already helped by sending lots of rain to help leach out salt from the soils.  We can help maintain the ideal soils by adding worm castings and compost to our soils.

Using pH to grow healthy plants in our gardens

Edible plants prefer pH 5.5 to 7.  These include beans, broccoli, cabbage, carrot, cucumber, squash, turnips, tomatoes and sweet corn.

Acid loving plants prefer pH 4 to 5.5.  These include blueberries, epiphyllum, cranberries, foxglove, azalea, camellia, gardenia, strawberries and hydrangeas. Most hydrangeas are white or pink, but we can change the color from pink to lavender to blue simply by applying aluminum sulfate to the soil.  In order to change the color dramatically, we need to drop the pH of the soils down to pH 4. We can grow these acid loving plants by using ” Azalea and Camellia soils mix”, which can be purchased from all the garden centers.

Plumerias, roses, citrus trees and fruit trees are happy in soils with pH 6 to 6.5.  When we grew Plumerias at the nursery, we mixed 10% peat moss to our soil mix.  Peat moss stabilizes potting soil to about pH 6.  Then we mixed Epsom salt into the water fertilizer system.

Now as a home owner, I use coffee ground to sprinkle on most plants to lower the pH in the soils, or you can use vinegar by mixing 2 tablespoon to one gallon of water.

Giving plants the correct pH is one of the tricks to making your plants healthy and happy.

Don’t forget to give Epsom salt to your Plumerias about 5 times during the growing season: once each month from April to August.

Have a happy gardening, Thank You.