From my root system's point of view, the difference between your actions is a matter of life and suffocation. When you overwater me, you are flooding my world. The air pockets in the soil disappear, and I cannot breathe. This leads to root rot, where my delicate white roots turn soft, mushy, and brown or black. They decay and fail in their primary duty: to absorb water and nutrients for the rest of the plant. Conversely, when you underwater me, my roots are left in a barren desert. They become dry, brittle, and may even shrink. I desperately search for any hint of moisture, but without success. My entire structure becomes weak because the roots cannot uptake the water necessary to keep my cells turgid and functioning.
My leaves are the most honest indicators of my distress. However, they can send confusing signals if you do not know how to interpret them. In the case of overwatering, my leaves will turn yellow, often starting with the older, lower leaves. This yellowing is a soft, often mushy decay. The leaf stalks and leaves themselves may feel soft and limp, and they will droop from a lack of oxygen and the onset of rot. They might fall off with the slightest touch. Underwatering tells a very different story. My leaves will also droop, but they do so as a dramatic, wilting plea for water. They will feel dry, thin, and brittle to the touch. Instead of a generalized yellowing, the edges will often turn brown and become crispy. This is a sign of tissue death from severe dehydration.
My flowers are my pride, my effort to reproduce and bring you joy. Both of your watering mistakes directly threaten this display. An overwatered environment is so stressful that I must abandon my reproductive efforts to focus on survival. I will direct energy away from my blooms, causing the existing flowers and developing buds to soften, rot, and drop from the plant prematurely. They may appear waterlogged and never fully open. Underwatering causes a similar flower loss but through a different mechanism. Without enough water pressure in my cells, the flower stems cannot remain upright. They will wilt dramatically, and the buds will dry out, shrivel, and abort before they ever get a chance to open, as I cannot support them without adequate hydration.
The medium I live in provides the most immediate clue. You must use your fingers to understand. For overwatering, the soil will feel constantly wet, cold, and soggy days after you watered. It may have a musty or unpleasant smell due to the anaerobic bacteria and fungi thriving in the waterlogged conditions. The pot will feel heavy. For underwatering, the opposite is true. The soil will pull away from the edges of the pot, becoming hard, compacted, and dusty. It will feel bone-dry to the touch several centimeters down. The pot itself will feel exceptionally light, a clear sign that it contains no water reserves for me to access.
