The Stromanthe triostar has become a highly sought-after houseplant, celebrated for its stunning foliage splashed with cream, green, and vibrant pink. This striking appearance and dramatic leaf movements often lead consumers and retailers to misidentify it as a type of Calathea. This article resolves the classification question, establishing the plant’s actual identity and detailing the precise botanical relationship it shares with its frequently mistaken cousin.
The Marantaceae Family: Defining the Relationship
The common mistake occurs because both Stromanthe and Calathea belong to the same overarching plant family, the Marantaceae, often called the “Prayer Plant Family.” This shared ancestry means both genera inherit distinctive traits, making them look and behave similarly in a home environment. Both are native to the tropical Americas, thriving as understory plants on the humid forest floor.
A key shared characteristic is the presence of the pulvinus, a joint-like swelling located at the base of the leaf blade. This specialized organ allows the leaves to move in response to light, a phenomenon called nyctinasty. During the day, the leaves lie flat to maximize light absorption. At night, the pulvinus adjusts, causing the leaves to fold upward, resembling hands clasped in prayer.
The colorful undersides of the leaves, frequently a deep purple or bright magenta, are another shared family trait. This coloration is thought to help the plant capture filtered light more efficiently in its shaded native habitat. Plants in the Marantaceae family, including both Stromanthe and Calathea, also grow from underground modified stems called rhizomes, contributing to their spreading, clumping growth habit.
Stromanthe vs. Calathea: Key Botanical Distinctions
Despite the many similarities inherited from the Marantaceae family, the Stromanthe triostar is definitively not a Calathea; it is a member of the Stromanthe genus. The two groups are differentiated by distinct characteristics that justify their separate taxonomic classification at the genus level. One easily observable difference lies in the growth habit of the plants.
Stromanthe species, including the ‘Triostar,’ typically exhibit a more upright and tree-like growth pattern. They often grow taller and develop more robust, woody stems than most Calathea varieties. Calathea species, by contrast, tend to remain more compact and clumped, with leaves emerging closer to the soil surface. The foliage of the Stromanthe triostar is generally more lance-shaped and robust, possessing the distinctive sectoral variegation.
From a scientific perspective, the most significant distinctions lie in the reproductive structures, specifically the flowers and seed capsules. Botanists rely on the subtle differences in the number and arrangement of the staminodes—sterile stamens—and the structure of the ovary to separate the genera. Although the plants rarely flower when kept as houseplants, these floral details are the ultimate evidence separating Stromanthe from Calathea. The Stromanthe genus is distinguished by a three-locular ovary, while many Calathea species possess a single-locular ovary.
Why the Confusion Persists
The mislabeling of Stromanthe triostar as a Calathea is primarily due to complex historical and commercial factors, not botanical error. For decades, the Calathea genus was a sprawling group that included hundreds of species, making it the most recognizable name within the Prayer Plant Family. Modern molecular and morphological studies prompted a significant reclassification of the Marantaceae family.
In this taxonomic shake-up, many species once classified as Calathea were moved to other genera, most notably Goeppertia, while the Stromanthe genus remained distinct. The plant trade has been slow to adopt these scientific changes, and many growers and retailers continue to use the familiar, though botanically inaccurate, name “Calathea Triostar” for marketing purposes. This persistent use of generic nicknames, such as “Prayer Plant,” which groups together Maranta, Ctenanthe, Calathea, and Stromanthe, reinforces the public’s confusion.