The popular name “Prayer Plant” is commonly used to describe several species of tropical foliage plants, a practice that frequently leads to confusion among enthusiasts. These plants are beloved for their striking, often highly patterned leaves and a unique daily movement that makes them appear to “pray.” This shared characteristic, which is visible to the naked eye, often overshadows the differences in their scientific classification, causing multiple distinct groups of plants to be mistakenly grouped under the same umbrella. To truly understand the relationship between the plant known as the Prayer Plant and the group referred to as Calathea, it is necessary to examine the specific scientific categories assigned to these plants.
Defining the Genera
The plant specifically designated as the true Prayer Plant is Maranta leuconeura, which is the classic species that originated the common name. This species is distinguished by its velvety, oval leaves, which typically display bright green variegation on the upper surface and a deep maroon or purple color underneath. Maranta is a distinct genus, separate from the numerous species that have historically been sold under the Calathea name.
The confusion stems from the fact that many plants commonly called Calathea also exhibit similar ornate foliage and the same daily leaf movement. However, the genus Calathea has undergone significant reclassification in recent years based on detailed genetic and morphological studies. Most species widely cultivated as houseplants, such as the Rattlesnake Plant and the Peacock Plant, are no longer classified as Calathea. Instead, they have been moved to the resurrected genus Goeppertia.
This taxonomic shift means that when referring to a houseplant Calathea, one is usually referring to a species now scientifically known as Goeppertia. Therefore, the true Prayer Plant (Maranta) is a member of a different genus entirely than the plants now classified under Goeppertia, even though they are frequently misidentified as the same or sold interchangeably. The formal reclassification of nearly 200 species into the Goeppertia genus provides a more accurate reflection of their evolutionary relationships.
The Shared Family Link
The similarity between Maranta and the plants formerly known as Calathea stems from their shared botanical family. Both Maranta and Goeppertia belong to the Marantaceae family, which is why they possess a similar overall structure and the characteristic leaf movement. This family, often known as the arrowroot family, is primarily composed of perennial herbs native to the tropical regions of the Americas, Africa, and Asia.
Plants within the Marantaceae family share several common morphological traits that contribute to their similar appearance and the collective use of the common name. They are typically rhizomatous, growing from underground stems, and their leaves are arranged in two distinct rows along the stem. A defining feature of this entire plant family is the presence of a specialized structure at the base of the leaf blade that facilitates movement, which is the root cause of the “praying” behavior. Although they are distinct genera, their common ancestry results in a striking uniformity of appearance and behavior.
The Science Behind the Movement
The phenomenon that gives the Prayer Plant and its relatives their name is a biological movement known as nyctinasty, or sleep movement, which occurs in response to the daily light-dark cycle. The leaves lie flat during the day to maximize light absorption and then fold upward at night, a process that is regulated by an internal circadian rhythm. This action is controlled by a small, thickened, joint-like organ located at the base of the leaf blade called the pulvinus.
The pulvinus contains specialized motor cells, which are divided into two opposing groups: flexor cells and extensor cells. The movement of the leaf is driven by an asymmetric change in the internal water pressure, known as turgor pressure, within these motor cells. To raise the leaf at night, the motor cells on the upper side of the joint lose turgor pressure, while the motor cells on the lower side gain turgor pressure, causing the joint to bend upwards.
Conversely, when the leaf opens in the morning, the turgor pressure changes in the opposite direction, causing the leaf to flatten out again. This rapid change in cellular volume is facilitated by the movement of ions, such as potassium, in and out of the motor cells, which in turn regulates the osmotic potential. This precise, pressure-driven mechanism allows the plant to adjust its leaf position throughout the day and night, regardless of its specific genus.