Monstera plants are celebrated for their large leaves featuring distinctive splits and holes, known as fenestrations. While many Monstera varieties develop splits along the leaf edges as they mature, a particularly sought-after characteristic is “inner fenestration.” This refers to holes that form entirely within the leaf blade, surrounded by intact green tissue, adding an intricate and visually striking element to the foliage.
Understanding Inner Fenestration
Inner fenestration describes holes completely enclosed within the leaf blade, distinct from marginal fenestrations which are splits extending from the leaf edge. These internal perforations are a hallmark of mature Monstera leaves, presenting as circular or oval openings surrounded by green tissue. The presence of inner fenestrations creates a “Swiss cheese” appearance.
The Science Behind Inner Fenestration
The formation of fenestrations is a natural developmental process, primarily attributed to programmed cell death (apoptosis). As a new Monstera leaf unfurls, specific cells within the developing leaf blade undergo this controlled process, creating holes before the leaf fully expands. Evolutionary theories suggest several adaptive advantages in the plant’s native rainforest environment. One hypothesis proposes that fenestrations allow sunlight to penetrate through upper leaves, reaching lower leaves more effectively, maximizing light absorption in a dense forest canopy. Other theories suggest fenestrations may reduce wind resistance during storms or help channel rainwater down to the plant’s root system.
Cultivating Inner Fenestration
Encouraging inner fenestration involves replicating optimal growing conditions. Bright, indirect light is crucial, as insufficient light inhibits fenestration development. Place the plant near an east or south-facing window, or supplement with a grow light, avoiding direct sun that might scorch leaves. High humidity (ideally 60-70%) is also beneficial for overall plant health and supports the unfurling of new leaves with fenestrations.
Providing a moss pole or other climbing support allows the plant to mimic its natural vining habit, encouraging larger leaves and fenestration as it matures. Patience is important, as inner fenestrations primarily appear on mature leaves, typically when the plant reaches about three feet tall or after a couple of years of growth. Consistent watering, allowing the top inch of soil to dry between waterings, and balanced fertilization during the growing season support the plant’s overall vigor, which is necessary for producing fenestrated foliage.
Monstera Varieties with Inner Fenestration
While many Monstera species develop fenestrations, some are known for their prominent inner holes. Monstera deliciosa is the most common and widely recognized species to exhibit significant inner fenestrations, especially as it reaches maturity and produces larger leaves. It is often referred to as the “Swiss Cheese Plant” due to its distinctive perforations.
Other Monstera varieties can also display inner fenestrations, though their appearance may vary. Monstera adansonii is known for its numerous oval-shaped internal holes, giving it a lacy appearance, and often develops fenestrations at a younger age than Monstera deliciosa. Monstera obliqua is famous for its extreme fenestration, often appearing almost skeletonized with very large internal holes, though it is rarer and more delicate to cultivate. Monstera standleyana can also develop internal fenestrations, contributing to its unique leaf patterns.