From our perspective beneath the soil, the difference between too much and too little water is a matter of life and death. When overwatered, our roots are essentially drowning. The soil becomes saturated, pushing out all the oxygen. We rely on oxygen in the soil pores for respiration, and without it, our root cells begin to suffocate and die. This creates a prime environment for root rot fungi to attack our now-weakened system. In contrast, underwatering leaves us desperately thirsty. The soil becomes hard and impenetrable, and our root hairs, which are responsible for water uptake, desiccate and die. We are unable to absorb the moisture and nutrients we need to sustain the rest of the plant, leading to a systemic shutdown.
You often see our distress first in our leaves, but the type of wilting tells a different story. In cases of underwatering, our leaves wilt as a direct result of water deficit. The cells lose turgor pressure, causing the leaves and stems to droop and feel dry and crisp to the touch, particularly at the edges. We are conserving the last vestiges of moisture. When overwatered, we also wilt, but this is because the damaged, rotting root system can no longer transport water to the leaves, even though the soil is wet. The leaves may feel soft, limp, and even cool or clammy, not dry. They might also show oedema, where cells burst from taking in too much water, appearing as blister-like bumps.
The color and condition of our foliage provide critical clues. Overwatering leads to a very specific pattern of chlorosis, or yellowing. The older, lower leaves are often the first to turn a uniform yellow before they drop off. This is because we are sacrificing the oldest growth in a futile attempt to survive the root crisis. The yellowing is often widespread and can be accompanied by a limp, lifeless texture. Underwatering, however, causes leaves to become dry, brittle, and brown, typically starting at the tips and margins before the entire leaf crumbles. Leaf drop will occur, but the leaves will be dry and crispy when they fall, not soft and yellow.
Our overall growth and flowering capabilities are severely impacted by both extremes. When consistently overwatered, our growth becomes severely stunted. New stems may be weak and spindly, and the formation of flower buds is drastically reduced or ceases altogether. Our energy is diverted to a failing root system rather than to reproduction. Underwatering similarly halts growth and flowering, but the pattern is different. We enter a state of preservation, where all non-essential functions stop. New buds may form but will often abort, dry out, and fail to open, or the flowers will be significantly smaller and fade quickly as we cannot support them.
The environment immediately around us offers the final confirmation. Overwatered soil will feel consistently wet, cold, and compacted for long periods after watering. A musty or sour smell may emanate from the soil, indicating anaerobic conditions and root decay. This environment also attracts pests like fungus gnats. Underwatered soil, on the other hand, will pull away from the edges of the pot or become hard, cracked, and dusty on the surface. It will feel bone dry deep into the root zone and will require significant effort to rehydrate, as it may initially repel water.
