The term “calcarium” is not a standard gardening term. It appears to be a misnomer, with the likely intended subject being “calcareous soil” or the role of calcium in a garden environment. This article will explore the characteristics of calcareous soils and their impact on plants, along with practical gardening approaches for these specific soil conditions.
Understanding Calcareous Soil
Calcareous soil is defined by the presence of a significant amount of calcium carbonate (CaCO3). These soils exhibit an alkaline pH, typically ranging from 7.5 to 8.5, and can exceed 9 if sodium carbonate is present. They commonly form in arid and semi-arid regions where insufficient rainfall prevents the leaching of soluble salts, leading to calcium carbonate accumulation from parent materials like limestone, atmospheric dust, or weathered calcium-rich sedimentary rock.
The high calcium carbonate content in calcareous soils often affects soil structure, forming hard layers called “caliche” that impede water and root penetration. While these soils can be well-drained, especially if sandy, their alkaline nature influences nutrient availability. Many essential plant nutrients, particularly micronutrients like iron, zinc, and manganese, become less soluble and less available to plants at high pH levels. Phosphorus availability is also reduced, as it forms insoluble calcium phosphate compounds.
Plants and Calcareous Soil
Plants respond differently to calcareous soil conditions. Those that thrive in high pH, calcium-rich environments are known as “calciphiles” or “calcicoles.” These plants have adapted physiological mechanisms to cope with high calcium and acquire nutrients less soluble in alkaline conditions.
Conversely, “calcifuges” are plants that do not tolerate alkaline soil. These plants struggle in calcareous soils due to nutrient deficiencies, even when nutrients are present. A common issue for calcifuges is iron chlorosis, where leaves turn yellow between the veins while the veins remain green. This occurs because iron becomes less soluble and less available for plant uptake in high pH conditions.
Gardening in Calcareous Soil
Gardening in calcareous soil begins with understanding its specific characteristics. Soil testing is an important step to determine pH and nutrient levels, guiding plant selection and amendment strategies. While it is possible to lower soil pH, altering naturally calcareous soil on a large scale is challenging and temporary due to calcium carbonate’s buffering capacity.
The most effective approach is to select plants that tolerate or prefer alkaline conditions. Many common garden plants thrive in soils with a pH between 7 and 8. For acid-loving plants, container gardening offers a practical solution, allowing for a controlled, acidic soil environment using specialized potting mixes. Amending soil with organic matter can slightly acidify the soil as microbes decompose the material, releasing carbonic acid.