From our root system's point of view, water is life, but its balance is everything. When overwatered, the soil around us becomes perpetually saturated. This drives out the vital air pockets we need for respiration. We essentially begin to drown and suffocate. Without oxygen, our cells die, and we become soft, brown, and mushy. This condition, root rot, prevents us from absorbing any water or nutrients at all, creating a cruel paradox where the plant is drowning yet dying of thirst.
Conversely, when underwatered, we become desperate. The soil medium becomes bone dry and may even shrink away from the sides of the pot, leaving us exposed. To conserve the plant's precious resources, we desiccate. We turn brittle, thin, and papery. Some of us may die back entirely. Our primary function is absorption, and without moisture, we cannot transport water and dissolved minerals up to the stems and leaves, forcing the entire plant into survival mode.
As an Orchid Cactus (Epiphyllum), my stems are designed to store water. They are thick, fleshy, and photosynthetic. When overwatered, the signals from the compromised roots cause chaos. The water pressure within our cells becomes too great. The outermost layers, the epidermis, may split or develop translucent, water-soaked spots. We become overly swollen, soft to the touch, and may turn a sickly yellow-green color as our chlorophyll breaks down and the tissue begins to necrotize from the inside out.
When underwatered, the story is one of loss and contraction. Without a steady supply from the roots, we must consume our own internal water reserves. We begin to shrivel, wrinkle, and become noticeably thinner and flaccid. A healthy, plump stem will become limp and may start to fold or curl in on itself. The green color often fades to a dull, muted grayish-green or reddish hue, indicating severe stress. We are literally deflating.
From the plant's holistic perspective, both extremes trigger a shutdown of non-essential processes to focus solely on survival. In an overwatered state, the energy required to combat root rot and fungal infections is immense. Consequently, all new growth ceases. You will see no new flat stems (phylloclades) emerging. Most critically, the plant will abort any existing flower buds. Investing energy in reproduction is impossible when the core systems are failing; the buds will yellow and drop off.
In an underwatered state, the strategy is similar but for a different reason. Growth is halted to prevent further water loss through transpiration from new tissue. The plant enters a state of stasis, merely existing rather than thriving. While it may hold onto flower buds longer than an overwatered plant, the intense stress will often cause it to abort them anyway. If flowers do manage to open, they will be smaller and may wilt prematurely as the plant cannot support them.
