Plant color depends on pH of soil
Basically soil pH is a measure of how acidic or alkaline your soil is. Soil pH is measured on a scale of 1 to 14. If your soil has a pH value of less than 7 then you have acidic soil. On the other hand if your soil has a pH value of greater than 7 then you have alkaline soil. A pH value of 7 is neutral, meaning you have neither acidic or alkaline soil.
The Effect of Soil pH on Plants
Knowing the pH value of your soil before planting is very important as it has a direct influence on the health of the plant. Each plant has its own recommended soil pH value range. The reason for this is that soil pH effects the availability of nutrients within the soil and plants have different nutrient needs. For example the nutrient nitrogen, a very important plant nutrient, is readily available in soil when the pH value is above 5.5. Similarily the nutrient phosphorous is available when the pH value is between 6 and 7. If a plant is placed into the wrong kind of soil it will be lacking in nutrients that it needs which will promote disease. In general the best pH value range for soil is approximately 6 or 7 as this is the range in which most nutrients can be readily available.
Finding Out pH of Soil
A quick way to find out the pH of an area is to look to see if there are any house hydrangeas (Hydrangea macrophylla) already growing in the area. If so observe the color of its flowers. A soil pH of 6 or below will produce blue flowers while a soil pH of 6.8 or higher will produce pink flowers.
How to Make Soil More Alkaline (Increase pH)
If your soil is acidic or slightly acidic you can take steps to make it more alkaline to accommodate the plants you want to put there. You can make your soil more alkaline (increase its pH value) by adding a form of lime. Lime is a compound of calcium or calcium and magnesium. It is usually applied in the form of ground agricultural limestone, burnt lime or hydrated lime (slaked lime). The smaller the limestone particles then the quicker your soil will become more alkaline.
How to Make Soil More Acidic (Decrease pH)
Some ornamental plants and fruit plants like blueberries require an acidic soil. To make your soil more acidic (decrease its pH value) you can use either aluminium sulphate or sulphur. Aluminium sulphate is the quickest acting as it will increase the acidity as soon as it disolves into the soil.