Plants in the Tradescantia genus, commonly known as wandering jew or inchplant, are popular houseplants due to their striking foliage and vigorous growth. Their diverse appearance, with leaves ranging from deep purple and silver to variegated pink and green, often leads people to question if Tradescantia is correctly categorized as a succulent. Answering this requires examining the biological traits that define a succulent plant.
Defining Succulent Traits
A succulent is defined by its specialized water-storage tissues, which allow it to survive extended periods of drought. These fleshy tissues, known as parenchyma cells, are typically found in the leaves, stems, or roots. Succulents minimize water loss in arid environments through unique adaptations. These include a thick, waxy outer layer, called a cuticle, and a reduced number of stomata, the pores plants use for gas exchange.
Many succulents also utilize Crassulacean Acid Metabolism (CAM), a modified form of photosynthesis where they open stomata only at night to conserve water vapor. These mechanisms enable plants like cacti and aloes to retain high water content, often 90–95% in some organs. The classification is based on this function of water storage, not on the plant’s evolutionary family.
The General Classification of Tradescantia
The majority of Tradescantia species are not classified as true succulents. These plants are native to the tropical and semi-tropical Americas and typically thrive in environments with consistent moisture. Common houseplant varieties, such as Tradescantia zebrina and Tradescantia fluminensis, lack the specialized water-storage tissues and extreme water conservation mechanisms found in true succulents.
Their stems and leaves are generally softer and more pliable, indicating a lower capacity for sustained water retention. They are fundamentally moisture-loving perennial herbaceous plants, though they can tolerate some neglect. Their classification places them in the Commelinaceae family, which is distinct from succulent families like Cactaceae and Crassulaceae.
Why Certain Species Cause Confusion
The question of succulence arises because some Tradescantia species possess morphological features that mimic true succulents. Notable examples include Tradescantia sillamontana and Tradescantia navicularis (sometimes known as Callisia navicularis). These species are exceptions within the genus and are considered the most succulent and xerophytic types of Tradescantia.
T. sillamontana, the white velvet plant, has fleshy leaves and stems covered in dense, fuzzy white hairs. These hairs protect the plant from intense sun and excessive evaporation in its native, arid Mexican habitat, giving it a succulent-like look. Similarly, the small, boat-shaped leaves of T. navicularis are thick and fleshy, storing more water than its common relatives. While these species are semi-succulent, their adaptation level places them outside the strict definition applied to desert-dwelling plants.
Practical Care Based on Classification
The non-succulent nature of most Tradescantia species dictates a care routine that contrasts sharply with cacti or sedums. The majority require consistently moist soil, but should never be left waterlogged, which quickly leads to root rot. They respond well to moderate watering, allowing the top half of the soil to dry out between applications.
Treating a typical Tradescantia like a desert succulent, by allowing the soil to dry out completely, will cause the foliage to wilt, become limp, and drop leaves. Conversely, semi-succulent species, like T. sillamontana, require a coarser, well-draining soil mix and should be watered sparingly, especially during winter dormancy, to prevent rot. The classification is a direct guide to ensuring the plant’s health and survival.