Agave Utahensis and the Calcicole Problem

Agave utahensis var eborispina growing from a solid limestone face.

Calciphile plants, also known as calcicoles, are a unique group of plants that thrive in soils rich in calcium carbonate. Agave utahensis is one such plant, as it grows almost exclusively on limestone-based soils.

The opposite is known as a calcifuge plant, Sarraceniaceae, carnivorous pitcher plants, are calcifuge plants.

Calcium-rich soils are characterized by excellent drainage, alkalinity, and low aluminum content, but are abundant in phosphorus and iron in addition to calcium. In contrast, calcifuge plants prefer acidic soils with higher aluminum levels and lower phosphorus and iron content.

Agave utahensis var nevadensis growing from limestone gravel.

For more than a hundred years—since 1918—Scientists have dedicated substantial research to unraveling the "calcicole problem," seeking to understand the factors that make certain plants calcium-loving or calcium-hating. However, a complete answer to this question remains elusive.

The preference for calcium-rich soils in calciphile in some plants may simply be attributed to their need for a well-drained substrate. And some plants may only grow on calcium soils on the fringes of their natural distribution range, indicating that they are more accurately called “calcium tolerant” than “calcium-dependent.”

Agave utahensis ssp uthaensis growing from sandstone.

Some, but not all agave are calcicole plants. Agave Utahensis, particularly its varieties Nevadaensis and Eborispina, stands out as a true calciphile. (Although remarkably, rare populations of the regular ssp. Utahensis can be found growing on sandstone)

Agave utahensis var nevadensis growing from mollisol.

My observations suggest that Eborispina tends to thrive at lower elevations, often growing from cracks in solid limestone surfaces. Nevadaensis frequently grows on mollisols, which are organic-rich soils atop limestone geology.