Soils with a high PH value between 7.1 - 8 are considered alkaline soils, soils over chalk or limestone will be alkaline or soils which contain a large proportion of builders rubble are also likely to have a higher PH level. Find out your soils PH level by using a PH testing kit. It is possible to raise the PH level of a soil by adding plenty of organic matter for example leaf mulch or well rotted garden compost, however soils over chalk or lime are usually untreatable. A large variety of plants will tolerate chalk and lime rather than trying to change the soils alkalinity it is better to work with your gardens soil and choose plants that will thrive under alkaline conditions.
Alkaline soil does provide benefits for those keen vegetable gardeners, since clubroot disease of the Brassica (cabbages) family is greatly reduced on alkaline soils. Lilacs, Wiegela, Madonna lilies and pinks all thrive on alkaline soils for example.
Acidifying materials include sulphur, sulphur dust acts more quickly than chips since acidifying using sulphur takes weeks to have an effect particularly when the soil is cold throughout winter time, it may take many months to have an effect, the finer the sulphur particles the faster acting it will be.
Aluminium sulphate is commonly used on Hydrangeas to obtain blue flowers when the soil conditions are not acidic enough to create blue flowers naturally. The effects are fast when used as a soil acidifier, however using large amounts or inaccurate qauntiites in the garden may unbalance phosphorus levels in soil, build up aluminium toxidity and excessively acidify soil levels. Ferrous sulphate also has acidifying qualities however when used in large quantities also leads to soil nutrient in-balance.
PH Values
PH 3.0 - 5.0 very acidic
PH 5.1 - 6 Acidic
PH 6.1 - 7 Moderately acidic
PH 7.1 - 8 Alkaline (7 being neutral)
If you are in doubt about your gardens PH levels particularly if you want to grow vegetables, Garden Doctor can provided soil analysis and advice regarding the best plants to grow in your garden.
