by Mary Finn

Created on: July 27, 2010   Last Updated: July 28, 2010

 PH is the measure of a soil's acidity or alkalinity - in chemical terms, the presence and type of certain hydrogen bonds. PH directly affects how plants use important nutrients, and whether they will grow at all. Some extreme conditions of alkalinity, like the borax filled deserts of America's Death Valley or extremes of acidity such as lakes filled with acid rain make growing nearly anything a challenge.

Fortunately, your garden is neither a desert nor a bog, so minor adjustments will probably be all that are necessary. Most plants grow best at a neutral PH, that is to say a PH of 7 on the scale of 0 to 14, the PH of pure distilled water. Most rainwater will be somewhat acidic since as it passes through the atmosphere it picks up carbon dioxide to form a mildly acidic substance called carbonic acid. In extreme cases, large amounts of carbon in the air such as those created by burning fossil fuels leads to so-called acid rain, the condition that has been killing fish in many formerly pristine mountain lakes and eating ancient marble statuary.

Gardeners may have their soil professionally tested for PH and mineral content or use one of many home testing kits. However, the educated eye can make a reasonable guess about the probable soil PH of a given area.

For example: How wet or dry is your area? If you are planning to xeroscape your land and plant native cacti, you probably are not surprised to learn that your dry land is somewhat alkali. That is to be expected in desert areas where rainfall is scarce. No water means little carbonic acid from rainfall. Additionally, the presence of certain underlying minerals such as limestone or borax, both of which are highly alkali and common in desert areas will add to the alkalinity. This soil will have a PH of greater than 7.

On the other hand, maybe your land is waterlogged. In that case, expect a lower PH of under 7. This low PH combined with water; means you may want to look at plants that like boggy ground, either that, or improve drainage before planting. Soil amendments that improve texture and aeration will be necessary. PH alone is not your sole concern. Lack of oxygen and the presence of plant pathogens that just love the moisture will be the primary concern here. Naturally-occurring peat in a true bog will significantly lower PH as will decaying leaves of many kinds.

How about an acid condition that is not really so extreme? Many plants, such as blueberries, azaleas and rhododendrons love mildly acid conditions

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