Mountain ranges vary in their soil types. Many ranges or individual mountains are rocky and have only small amounts of soil, but many also have plentiful amounts of soil. The United States Department of Agriculture divides soils into 12 orders, each with distinct features. Seven of these occur frequently in mountains. To understand how best to grow plants in mountainous areas, it is important to be able to identify what kind of soil you have and what its various strengths and weaknesses are.
Soils in the ultisol order occur mainly in the Southeast and contain large amounts of clay. This kind of soil is common in the Appalachian mountain range but can also be found in the Cascades of Washington and Oregon. It is often found in more humid climates. Ultisols are usually acidic and contain most nutrients in the upper few inches of the soil. They do not retain fertilizer well.
Inceptisols are some of the most common soils in mountainous regions. They can be found in the Appalachians, the Cascades, the Sierra Nevadas and the Rocky Mountains, although they are not as common there. The soils in this order are widely varied and occur in climates ranging from humid to semi-arid. This type of soil is not highly weathered and does not contain silicate clay.
Soils of this order are not found in many mountain ranges but do have a presence in the Cascades and the higher-altitude areas of the Rocky Mountains. Spodosols are often found under coniferous forests and are highly acidic and nutrient-poor. They are also low in organic matter.
Andisols are rich soils and hold nutrients and water very well. They frequently contain volcanic materials and can often be found in areas with greater-than-average amounts of rain. As such, it is unsurprising that they occur primarily in the Cascades. They are also present in the Rocky Mountains in northern Idaho.
Entisols are present in the Rocky Mountains and the southern Sierra Nevadas. They form in areas with high erosion, particularly steep slopes and dunes. They are often composed of materials like sand, metal oxides and clay.
Alfisols are scattered throughout various mountainous areas, especially the Appalachians and the Rocky Mountains. They are less common in the Cascades and the Sierra Nevadas. They often form under forests and contain clay in the subsoil (rather than close to the surface). They are often very good soils for agriculture.