Understanding acid or alkaline soil, #NaturesGOLD info…

3 min readAug 5, 2021

The pH scale indicates acidity or alkalinity. A soil with a pH number below 7 is acid, while one with a pH above 7 is alkaline. Garden plants typically grow best in neutral or slightly acid soil.

Most won’t thrive in highly acid or highly alkaline soil, though a few have adapted to such extremes.

In general, some nutrients cannot be efficiently absorbed by plant roots if soil pH is too high. If it is too low, on the other hand, nutrients may be taken up too efficiently: the excess cannot be processed fast enough and overloads a plant’s system, causing it to languish and die.

Soil pH and it matters…

If there’s one thing you should know about your vegetable garden, it’s the soil pH. The pH scale runs from 0 to 14, with 7.0 being neutral. Measurements between 0 and 6.9 are acidic, and those between 7.1 and 14.0 are alkaline. The target vegetable garden pH is 6.5.

Soil pH is important because…

1. pH is so important to plant growth because it determines the availability of almost all essential plant nutrients. At a soil pH of 6.5, the highest number of nutrients are available for plant use. See the USDA chart below for a visual explanation.

2. If the vegetable garden pH is too acidic, certain nutrients become less available, phosphorus in particular, while other nutrients, like aluminum and manganese, can become toxic. Acidic pH levels are also unwelcoming to beneficial soil bacteria.

3. Alkaline soils impede the availability of nutrients like iron, manganese, copper, zinc, and also phosphorous. Plants dependent on high levels of iron, evergreens in particular, perform poorly in alkaline soils.

Local climate gives you a clue to the likely soil pH. In high-rainfall areas, soils are often acid. It’s in these regions that you tend to find acid-loving plants like azaleas, rhododendrons, camellias, and blueberries. Alkaline soils, in contrast, are typically found in low-rainfall areas. Many of the plants popular for water wise gardens–sorts that need little water once they are established–do well in soil on the alkaline side. The olive, native to the Mediterranean basin, is one example of a plant that thrives in alkaline soil; oleander (Nerium oleander) and pomegranate also perform well.

If you’re not sure about your soil’s pH, you can test it yourself with one of the inexpensive test kits sold at most garden centers. Such kits can be relied on to tell you whether your soil is basically alkaline, acid, or neutral. If you suspect that your soil is highly alkaline or acid–or if a do-it-yourself kit so indicates–you may want to confirm the diagnosis with a professional soil test. Such tests are analyzed by laboratories; along with the results, you’ll normally receive recommendations for correcting the pH of the soil tested.