From my perspective, a rosemary plant, the single most important factor for my survival is the condition of my roots. They are my lifeline. When you overwater me, you are essentially drowning my world. The soil becomes saturated, pushing out all the air. My roots are suffocating; they cannot breathe. In this oxygen-starved environment, they begin to rot, turning soft, mushy, and dark brown. They are no longer functional and cannot take up water or nutrients, creating a cruel irony where I die of thirst while standing in water. Conversely, when you underwater me, my roots are desperately searching for any hint of moisture. They become dry, brittle, and may shrink. While they are still structurally sound (not rotten), they are simply unable to find the water they need to transport to the rest of my being.
My foliage will give you the clearest above-ground signs of my distress. If you have overwatered me, my normally firm, needle-like leaves will become soft and limp. They will droop and feel fleshy to the touch. The vibrant green will often fade to a pale, yellowish, or even brownish hue, starting with the older leaves closer to the soil. This is a sign of systemic failure and the onset of rot. In stark contrast, the leaves of an underwatered rosemary become dry and brittle. They lose all flexibility and will crumble easily when touched. The color turns from green to a dull, dusty gray-green and then progresses to a dry, crispy brown, often starting at the tips of the leaves and moving inward. The entire plant takes on a shriveled, parched appearance, as if it has been left in an oven.
My stems hold another key to diagnosing my condition. A healthy rosemary stem is woody, strong, and somewhat flexible. When I am suffering from too much water, the stems, especially newer, greener growth, may become soft and pliable. In advanced stages of root rot, the base of the stem may even feel soft and mushy. If you were to scrape the bark away, you might find a brownish, unhealthy tissue underneath instead of a fresh green or white layer. On the other hand, a stem from an underwatered plant is excessively dry and brittle. It may snap cleanly with very little bending, a sure sign of severe dehydration and a lack of water moving through my vascular system.
Finally, the environment you have placed me in—the soil—will always tell you the truth. The best way to understand my needs is to interact with the soil itself. For overwatered rosemary, the soil will feel consistently cold, wet, and clumpy to the touch, even several days after watering. The pot will feel surprisingly heavy due to the water weight. For an underwatered plant, the soil will pull away from the edges of the pot, becoming hard and compacted. It will feel dry and dusty to the touch, and the pot will be noticeably light, as if it contains barely any moisture at all. The best practice is to insert your finger a few inches into the soil; my ideal condition is to be watered only when the top few inches have become dry.
