This is one of those plant questions that seems contradictory until you understand what's actually happening. Snake plants — Sansevieria, or Dracaena trifasciata if you prefer the reclassified name — are famously drought tolerant. Overwater them in soil and they rot. Yet you can propagate a cutting in a glass of water and it will happily grow roots. How does that make sense?
The answer is oxygen.
What roots actually need
Roots don't just absorb water and nutrients — they respire. Like every living tissue in a plant, roots require oxygen to carry out cellular respiration, the process that generates the energy needed to grow, absorb nutrients, and maintain cellular function. Cut off the oxygen supply and root cells begin to die.
This is why waterlogged soil is lethal. The problem isn't the water itself — it's that water has displaced the air. Healthy soil is roughly 25% air by volume. Those air pockets are what make oxygen available to roots. When soil becomes saturated, those pockets fill with water and the oxygen disappears. Roots suffocate.
It gets worse. Saturated, oxygen-depleted soil creates the perfect conditions for anaerobic bacteria and pathogens — organisms that thrive without oxygen. These are responsible for the soft, brown, foul-smelling rot that kills overwatered succulents. The rot isn't caused by water directly. It's caused by what water does to the soil environment.
Why soil structure matters
Fresh potting mix has texture — coarse particles, organic matter, perlite or sand creating spaces between the components. Water flows through it, then drains, leaving those air pockets intact.
Over time, soil degrades. Organic matter breaks down, particles compact, and the mix loses its structure. What was once a well-draining medium becomes dense and fine, holding water far longer than it should. The same watering schedule that worked when the plant was first potted becomes dangerous a year or two later when the soil has compacted.
This is why repotting matters — not just because roots need more room, but because fresh mix restores the gas exchange that roots depend on.
So why does water propagation work?
Plain water contains dissolved oxygen. Tap water that has been sitting in a glass has absorbed oxygen from the air at the surface. The concentration is low compared to soil air, but it's enough — especially for a cutting that hasn't yet developed the metabolic demands of a full root system.
More importantly, water propagation works precisely because there's no soil to compact, no anaerobic bacteria to colonise, and no degraded medium trapping moisture against the tissue. The cutting sits in a clean, oxygenated environment. When you change the water regularly, you're not just keeping it fresh — you're replenishing the dissolved oxygen.
The roots that form in water are also structurally different from soil roots. They're adapted to a low-oxygen aquatic environment and are often more succulent and less branched. This is why plants propagated in water can struggle when moved to soil — they need time to develop a different root architecture suited to gas exchange in a solid medium.
What this means for how you care for plants
Water less than you think you need to. Let soil dry out between waterings — not just at the surface, but through the pot. Lift the pot; if it feels light, water. If it still feels heavy, wait.
Repot every two to three years regardless of whether the plant looks rootbound. Fresh soil isn't a luxury — it's infrastructure.
And if you're seeing rot, the instinct to water more carefully next time is right — but also check the soil. Compacted, degraded medium will rot roots no matter how careful you are.