Orchid Cactus, the common name for hybrids primarily within the Epiphyllum genus (and closely related genera like Disocactus and Selenicereus), are celebrated for their breathtaking nocturnal blooms. Identifying the multitude of varieties can be complex due to extensive hybridization, but focusing on key botanical characteristics provides a clear path to differentiation.
The primary vegetative structure is a modified, photosynthetic stem called a cladode. While often flat and leaf-like, its morphology offers initial clues. Examine the stem's edges: some varieties have deeply serrated or undulating margins with pronounced notches, while others are almost smooth with barely any indentations. The central midrib, a vestige of the stem's structure, can be very prominent and woody or relatively subtle. Furthermore, observe the areoles—the small, fuzzy bumps from which flowers, branches, and sometimes spines emerge. Their size, spacing, and color (often brown or white) can vary between cultivars.
Flower characteristics are the most definitive for identification. Precise observation during bloom is essential. First, note the flower's form: single, double, or peony-type, which refers to the number and arrangement of petals and petaloids. Second, measure the flower's diameter, as it can range from a few inches to over a foot in spectacular varieties like 'Queen of the Night' (Selenicereus grandiflorus). The shape of the floral tube (the long structure connecting the flower to the stem) and the length of the exerted stamens (pollen-bearing organs) are critical diagnostic features for experts, often distinguishing between pure species and complex hybrids.
This is the most apparent differentiator for hobbyists. Orchid Cactus blooms exhibit a stunning array of colors and patterns. Carefully note the base color of the outer perianth segments (sepals) and inner segments (petals). Beyond a single hue, look for complex combinations: bicolors with a clear distinction between two colors, blends where colors gradient into one another, and picotees which have a solid colored margin. Many varieties also feature intricate venation or striping in a contrasting color, radiating from the throat of the flower outward. The color of the stigma lobes (the pollen-receptive part of the pistil) is also a stable trait, often being white, yellow, or green.
The overall growth pattern of the plant provides additional context. Some varieties, particularly those with Disocactus ancestry, have a more upright or arching habit, with stems that are woodier at the base. Others, especially epiphytic Epiphyllum types, have a distinctly pendant or cascading growth habit, making them ideal for hanging baskets. The rate of growth and the tendency to produce basal shoots or aerial roots can also be indicative of certain genetic lineages.
