The Monstera deliciosa, often called the Swiss Cheese Plant, is a popular houseplant known for its large, distinctive fenestrated leaves. When this plant begins to grow horizontally or lean severely to one side, it can be a source of worry for the owner. This sideways growth, however, is not a sign of distress but rather a display of the plant’s natural instincts at work indoors. The leaning is rooted in the plant’s biology and its reaction to common household conditions. Understanding these causes is the first step toward correcting the growth pattern and encouraging your Monstera to grow vertically once more.
Understanding Monstera’s Natural Growth Habit
The Monstera deliciosa is naturally a hemiepiphyte, meaning it starts its life rooted in the soil but quickly seeks to climb the trunks of larger trees in its native tropical forest habitat. This climbing habit is for survival, as it allows the plant to reach the brighter canopy light filtering through the dense jungle undergrowth. The plant uses specialized aerial roots, which emerge from the stem nodes, to attach itself firmly to a support structure.
This drive to move is governed by two distinct biological responses to light and shadow. The first is phototropism, the instinct for a plant to bend its stems and leaves toward a light source to maximize photosynthesis. The second is skototropism, or negative phototropism, which is the plant’s instinct to grow toward darkness or shadows. This shadow-seeking behavior helps the young Monstera find the trunk of a large tree so it can begin its vertical ascent to the light.
This biological programming explains why an indoor Monstera may not grow straight upward unless it is provided with a clear, stable vertical target. When these natural climbing and light-seeking mechanisms are triggered indoors without the proper support, the plant translates its natural vertical climb into a horizontal sprawl or a significant lean.
Identifying Environmental Triggers for Leaning
The most common reason an indoor Monstera begins to lean is unilateral light exposure, which is light coming predominantly from a single direction, such as a window. Phototropism causes the plant to aggressively stretch and bend its stem and leaf petioles toward this sole light source, resulting in a distinctly lopsided appearance. If the plant is not regularly rotated, this constant bending can physically alter the main stem’s structure over time.
A lack of adequate support is another major contributor to sideways growth. As the Monstera matures, its large, heavy leaves and thick vining stems create a significant amount of weight. Without a moss pole, trellis, or other structure to anchor its aerial roots and distribute this weight vertically, the entire plant becomes top-heavy and collapses to one side. The aerial roots, unable to find a vertical surface, may sprawl or attempt to anchor themselves into the soil.
Furthermore, issues with the plant’s foundation can exacerbate the leaning problem. If the Monstera is in a pot that is too small for its size, the root ball may lack the necessary anchorage to support the plant’s considerable above-ground mass. A top-heavy plant in a small or lightweight pot is structurally unstable and can easily tip or lean under its own weight, especially as the soil dries and becomes lighter.
Practical Methods for Straightening the Plant
The most effective method for correcting sideways growth and encouraging a vertical habit is by providing a stable, tall support structure. A moss pole or coir pole is ideal because it mimics the humid, textured bark of a tree, which the aerial roots can naturally latch onto and climb. When installing the pole, place it deep into the pot, positioning it behind the main stem where the aerial roots emerge.
Once the support is in place, gently guide the main stem of the plant toward the pole. Use soft plant ties, velcro, or garden twine to secure the stem loosely to the support, making sure not to cinch the stem or the leaf petioles too tightly, as this can cause damage. For an already leaning plant, this process may need to be done gradually over several weeks to avoid snapping the hardened stem. Keeping the moss pole moist encourages the Monstera’s aerial roots to grow into the pole, creating a stronger, self-sustaining anchor.
To counteract the effects of unilateral light exposure, establish a consistent rotation schedule for the plant. Rotating the pot by a quarter turn every week or two ensures that all sides of the plant receive equal access to the light source. This action prevents the plant from continuously stretching toward one direction, encouraging more balanced and compact growth.
If the plant is severely top-heavy, strategic corrective pruning can rebalance its weight distribution. Pruning involves removing the longest, most sprawling stems or any overly heavy, older leaves that contribute to the lean. This not only makes the plant lighter but also directs the plant’s energy toward new, more vertical growth near the central stem. Finally, if the plant’s base seems unstable, repotting into a slightly larger, heavier container with fresh, well-draining soil can provide the necessary foundation and stability.