Aerial roots are roots that grow above the ground, emerging from stems, branches, or trunks instead of from underground. They serve different purposes depending on the plant: absorbing moisture from the air, anchoring a climbing vine to a wall, propping up a massive tree, or delivering oxygen to roots buried in waterlogged soil. If you’ve noticed thick, cord-like growths dangling from a Monstera or a banyan tree, those are aerial roots doing exactly what the plant designed them to do.
How Aerial Roots Differ From Underground Roots
All aerial roots are a type of adventitious root, meaning they sprout from tissue that isn’t part of the plant’s primary root system. A typical root grows downward from a seed. Adventitious roots bypass that entirely, forming from stems, nodes, or branches in response to the plant’s environment. They share many of the same functions as underground roots, including water uptake and structural support, but they develop from above-ground tissue and often have specialized anatomy to handle life in open air.
Some plants produce aerial roots as a normal part of their growth cycle. Others develop them as a stress response to flooding, physical damage, or high humidity. The hormonal signals that trigger aerial root growth overlap with those that drive underground root branching, but the triggers themselves are different, often environmental rather than developmental.
Types of Aerial Roots and What They Do
Prop Roots
Prop roots grow from horizontal branches and extend vertically downward toward the soil, looking like long poles holding up a canopy. The banyan tree is the classic example. A single banyan can send hundreds of prop roots from its branches to the ground, where they thicken into trunk-like columns. This allows the tree to spread laterally far beyond what a single trunk could support. Fig trees use the same strategy.
Stilt Roots
Stilt roots emerge from the base of the main stem and grow outward at an angle, like ropes anchoring a tent. They’re shorter and thicker than prop roots and serve a different structural purpose: keeping the plant upright in unstable ground. Mangroves and pandanus palms rely heavily on stilt roots to stay standing in soft, waterlogged soil where a conventional root system would offer poor anchorage.
Climbing Roots
English ivy uses aerial roots not for nutrition but for grip. Its attachment roots follow a surprisingly complex four-phase process. First, they make physical contact with a surface. Then they flatten and squeeze into tiny gaps in the substrate. Next, the root hairs secrete a glue-like adhesive substance. Finally, as the root hairs dry out, they curl into spoon-shaped tips due to the arrangement of structural fibers in their cell walls, physically hooking into surface irregularities. The combination of chemical glue and mechanical anchoring is strong enough to damage masonry over time.
Absorptive Roots
Epiphytic orchids, which grow on tree branches rather than in soil, have aerial roots wrapped in a spongy outer layer called velamen. This tissue is made of dead cells at maturity and works like a paper towel: it captures water and dissolved nutrients within seconds of a rain event. The velamen also holds charged nutrient ions in place, giving the living inner root tissue time to absorb them efficiently. Beyond absorption, this spongy coating reduces water loss between rain events, shields the root from UV damage, and insulates against heat in exposed tropical canopy conditions.
Breathing Roots
Mangroves face a unique problem. Their underground roots sit in oxygen-starved tidal mud, yet root cells need oxygen to survive. The solution is pneumatophores: vertical aerial roots that poke above the waterline or mud surface. These roots have small pores called lenticels on their exposed surfaces that let atmospheric oxygen in. Inside, gas-filled channels called aerenchyma act as structural conduits, piping oxygen downward from the exposed tip all the way to the buried root ends with very little resistance. Some oxygen escapes along the way, but enough reaches the root tips to keep the plant alive in conditions that would suffocate most other species.
Why Humidity Drives Aerial Root Growth
If you’ve ever noticed your Monstera or pothos producing more aerial roots in summer or in a humid bathroom, that’s not a coincidence. A 2023 study tested three common houseplant species from the Araceae family (the group that includes Monstera, pothos, and philodendron) under high and ambient humidity levels. All three species grew more overall in high humidity, but aerial roots showed the greatest biomass increase of any plant structure measured. The humid air essentially mimics the tropical understory these plants evolved in, signaling that conditions are favorable for aerial root development.
This also explains why the same plant might produce almost no aerial roots in a dry, air-conditioned room but sprout several in a greenhouse or terrarium. The roots aren’t a sign of distress. They’re a sign the plant is comfortable enough to invest energy in them.
Managing Aerial Roots on Houseplants
Monstera deliciosa is the houseplant that prompts the most questions about aerial roots, since it can produce thick, woody roots that grow several feet long. These roots are a normal, healthy part of the plant’s growth. In the wild, they anchor the Monstera to trees and absorb moisture from the surrounding air.
Cutting aerial roots is safe and won’t harm the plant. It will continue producing new leaves and new aerial roots afterward. If you trim them, use clean scissors and cut close to the stem. The plant treats it the same way it would treat any minor pruning.
A better option, if you’re willing, is to guide the aerial roots into a moss pole or even into the soil of the pot. Directing them into a moist support gives the plant something to grip, which encourages larger leaf growth and a sturdier stem. Routing them into soil lets the plant expand its root system, which supports bigger, healthier growth overall. Trimming is purely an aesthetic choice, but redirecting aerial roots gives the plant a functional advantage.
Aerial Roots in the Wild
The scale of aerial root systems in nature dwarfs anything you’d see on a houseplant. A mature banyan tree can cover acres of ground using prop roots alone, with individual roots thickening to the diameter of tree trunks. Mangrove forests along tropical coastlines are essentially held together by networks of stilt roots and pneumatophores, creating a tangled root architecture above the waterline that buffers shorelines from storm surges and provides habitat for fish and crustaceans.
Strangler figs take aerial roots to an extreme. They germinate in the canopy of a host tree, send aerial roots downward to the soil, and gradually encase the host trunk in a lattice of thickening roots. Over decades, the fig’s root network can compress and shade out the host entirely, leaving the fig standing on a hollow column of its own fused roots. It’s one of the more dramatic examples of how aerial roots can reshape an ecosystem rather than simply respond to one.