The various pH levels within soil and water affect the vitality of shrub growth. Soil acidity directly affects the way nutrients are absorbed within a plant---nutrients that are important to every physiological process that the plant experiences. Plants that are unable to absorb nutrients will experience stunted growth and a gradual death.
All soils are measured by their acidity on a scale known as the pH scale. The scale ranges from 1 to 14 with 7 being neutral. Anything below 7 is considered acidic, while anything above is alkaline. Most shrubs need soil between 5.5 and 6.5 to properly thrive.
Water tends to be more acidic in nature, causing moist soil with a lot of decomposing material and volcanic origins to be acidic. Drier soils containing sedimentary rocks are more alkaline.
Most gardening stores sell standard pH soil test kits that will help you determine the acidity level of your garden. Soil amendments are available on the market that can also help alter the pH levels within your garden.
Rhododendrons, mountain laurel, blueberry, azaleas, juniper and silver bell are all shrubs that naturally grow well in acidic soil. They require moist soil like loam that is able to retain moisture for long periods of time.
There are various shrubs that grow well in alkaline or neutral soil. Some of these include lilac, snowberry, chokeberry, ninebark, viburnum, red twig dogwood, highbush cranberry, willow and forsythia.
Amending soil levels to best suit your shrubs is possible. Soil pH is raised by introducing other substances into the environment. Compost topped with wood chip mulch can lower levels to increase acidity, while ground limestone or wood ashes will raise alkaline levels.