Planting in Medium Soils
While it may be tempting to gloss over medium soil types, writing them off as standard, default garden soil, the category of medium soils warrants attention and appreciation.
Most gardeners, wherever they live, are likely to encounter medium soils. However, there is a huge diversity in the types of soils that fall under this category. Moreover, medium soils are typically critical in transitions from wetlands to drier sites, acting as a sponge to aid in water sequestration and dispersion. Plants that prefer medium soils are often selected for use in rain gardens, as they are able to tolerate the seasonal variability in moisture that most wetland plants are unable to tolerate.
Medium soils can vary considerably in their soil texture as well as many other factors. Soil texture is the relative proportion of sand, silt, and clay in the soil. Sand has the largest particle size while silt particles are medium sized and clay particles are the finest. The size of these particles impacts how water is retained; coarse textures tend to be well-drained while fine textures tend to be more moisture retentive. Loam is a well-known example of a medium soil texture. Other examples include silt, silt loam, sandy loam, and sandy clay loam.
Another important factor that affects soil is organic content, also known as humus. Humus is a dark soil material created by the microbial decomposition of plant and animal matter, namely leaves. Humus is rich in essential plant nutrients such as carbon, nitrogen, phosphorus, potassium, magnesium, calcium, and sulfur. Soils that are high in organic content are typically referred to as rich soils while soils that are low in organic content are called either poor or lean soils. Different plant species prefer different levels of soil organic content. For example, wild ginger (Asarum canadense) is a species that likes to grow in shaded, medium soils. However, it will not grow in shaded, medium soils that are low in organic content. It requires shade, medium soil moisture, and high soil organic content in order to be able to grow. Conversely, some plant species prefer poor soils. These species may be able to tolerate higher soil organic content but are typically outcompeted by other species that are better adapted to the high nutrient levels associated with these soils.
Other factors that affect medium soils include pH, slope, elevation, and proximity to water. For example, some plant species prefer well-drained soil close to a water source while other species prefer less well-drained soil with less water input, and both might fall under the medium category. Medium soil types offer a staggering diversity of plant species for gardeners to choose from, though it is important to consider all applicable factors when selecting a planting’s composition.
