Different Soil Conditions: Acid Soil and Plants that Depend on It
65Different Soil Conditions
Soils vary widely in their level of acidity or alkalinity and the structure of their particles, which range from light sand to heavy clay. these factors determine how much moisture and nutrients they contain.
Acid Soil
This type of soil can be free draining and sandy, heavy and sticky, or even organic with a high peat content. Clay soils are often acid, and peaty soils, where the organic matter has not decomposed, are almost always acid.
Some soils, even if originally alkaline, can gradually become more acid as a result of the lime being washed out of the upper layers close to the soil surface. This is because rainwater is slightly acidic, and it dissolves the lime in the soil and washes (leaches) it down through the soil. As a result, soils in high rainfall areas are more likely to be acid than alkaline.
Plants that Depend on Acid Soil
Most plants that grow naturally on acid soils (known as calcifuge) usually struggle when grown in anything else. This is because they are unable to take up enough iron from an alkaline soil.
Some excellent garden plants grow only in acid soil, so if your garden has this condition, you can look forward to growing some real treasures.
Acid soils are generally not a problem to plant because in addition to those plants that prefer them, many plants also tolerate them. If your soil is not very acid and your climate isn’t too wet, there is little restriction on what you can grow, although it may be wise to avoid Mediterranean plants such as Cistus and lavender which thrive in dry alkaline conditions.
Many evergreen shrubs will grow on acid soil. The glossy ovate green leaves of rhododendrons, azaleas, camellias and skimmias provide wonderful backdrops for their often startlingly bright blooms that provide colour from mid-spring through the early summer. Pieris has the added attraction of red-flushed young leaves.
Permanent foliage plants also include ground covers and creeping plants like gaultherias, heathers and heaths.
Deciduous trees growing on acid soils produce some stunning autumn foliage colour. Outstanding among these are the maples (Acer). Many of the spring- and summer-flowering deciduous shrubs also have good autumn colour.
Plenty of perennials and annuals that grow on a wide range of soils can be used to provide seasonal highlights for the border. Wake robin, Himalayan blue poppies and lupins, however, require a slightly acid soil.
Year-round Interest
Acid-loving shrubs are often associated with their stunning spring flowers. The showy white, pink, red or yellow flowers of camellias, rhododendrons and azaleas bloom in abundance and are deservedly much admired. The waxy beauty of magnolia blooms, in cream or blush, is breathtaking. Witch hazels produce their surprisingly frost-resistant and fragrant, spidery blooms, in yellow to dark red, from midwinter to early spring.
Many deciduous shrubs, including maples and witch hazels, are prized for their autumn foliage colour. And there are berries, too. Several species of Gaultheria produce white or purple-red fruit at this time. Some shrubs also have attractive bark.
For colour through spring and summer try Wake robin, Himalayan blue poppies and lupins.
Heathers form stunning carpets of flower colour in late summer and autumn. Many varieties are grown for their foliage, which changes colour during the year.
- Soil Types - Important for Plant Growth
Soil types Mineral soils are derived from the long-term chemical and mechanical breakdown of the earth's crust, a process which has been going on for millions
Neutralizing Acid Soil
Adding lime to the soil is an easy and effective way to reduce the acidity. However, it needs to be applied to ground that is bare of plants, dug in and left to break down for several weeks at least, or preferably longer. This is only really practical on vegetable plots, which can be left bare during the winter.
Lime should never be applied at the same time as fertilizer, as the lime will cause the fertilizer to break down too quickly. It can be used when renovating or making a new border, but most ornamental plants tolerate moderately acid soil, so it is not generally worthwhile trying to neutralize acid soil in order to grow acid-hating ornamentals in your garden.
An alternative to liming is to incorporate spent mushroom compost, which is rich in lime. You may even have the benefit of a small crop of mushrooms, as there are often spores in the compost.
Correcting acid soil - click here
