From a botanical perspective, the fundamental difference between Passiflora incarnata (Maypop) and Passiflora edulis (the common edible passion fruit vine) lies in their growth habits and vigor. P. incarnata is a temperate species that is deciduous and often dies back to the ground in winter, even indoors if allowed to go dormant. It is a rampant, sprawling grower that can quickly cover a large area with its runners. In contrast, P. edulis is a tropical evergreen that requires consistent warmth. It is a fast-growing but more typical climbing vine, attaching via tendrils. For indoor cultivation, P. edulis demands a very large, sturdy trellis and frequent pruning to manage its size, while the less woody P. incarnata may be easier to control but requires a winter rest period.
The intricate flowers are the passion flower's most defining feature, and their structure varies significantly between varieties, directly impacting indoor success. The complex bloom of P. incarnata is typically ornate with pinkish-white petals and a prominent corona. Crucially, many varieties, especially the wild species, are self-sterile or require specific pollinators like large bees for fruit set. This presents a major challenge indoors. Conversely, selected cultivars of P. edulis, such as 'Frederick', are often self-fertile. This means a single plant can pollinate its own flowers, a critical advantage for an indoor grower who must manually pollinate using a small brush to transfer pollen from the anthers to the stigma.
The physiological process of fruiting is a key differentiator. While both can produce fruit indoors, Passiflora edulis is unequivocally bred for fruit production. Its entire physiology is geared towards generating the large, juicy, purple or yellow passion fruits. Achieving this indoors requires providing intense, direct light (often requiring supplemental full-spectrum grow lights), high humidity, and consistent feeding to support the significant energy expenditure of fruit development. P. incarnata produces smaller, egg-sized maypops. While still requiring good light to fruit, its needs are generally less demanding than those of P. edulis. However, its fruiting success is entirely contingent on successful pollination, which is harder to achieve indoors without the correct pollinator.
Each variety has evolved with distinct environmental preferences. Passiflora edulis, being tropical, thrives in consistently warm temperatures (65-85°F or 18-29°C) and high humidity levels above 50%. It is highly sensitive to cold drafts and sudden temperature drops, which can trigger leaf drop and stress the plant, making it susceptible to pests like spider mites. Passiflora incarnata is far more adaptable to temperature fluctuations due to its temperate origin. It can tolerate cooler indoor conditions and lower humidity levels. Its response to winter is to enter dormancy, a natural state of energy conservation that involves leaf loss, which is often mistaken for a dying plant but is a normal part of its annual cycle.
