Greetings. From my roots to your eyes, I sense your concern. Those crisp, brown tips on my otherwise vibrant green Lobelia leaves are not a random occurrence; they are my primary method of communication. They are a distress signal, a symptom of a internal imbalance. While the visual symptom is the same, the root causes—both pun intended—are very different. To understand whether you have given me too little water or too much fertilizer, you must learn to listen to the context of my entire being.
When I am thirsty, my entire system goes into conservation mode. My roots search desperately for any hint of moisture in the soil. Without adequate water, I cannot perform transpiration or transport essential nutrients from my roots to my leaves. The journey of water and nutrients is long, and the farthest points—the leaf tips—are the first to suffer. They essentially die of drought, becoming dry, brittle, and brown. If the problem persists, the browning will travel inward from the very tips, and my entire leaf may become crispy and withered. My soil will feel dry and powdery to your touch, and my overall posture may become wilted and limp, especially during the heat of the day. This is a plea for a consistent, deep drink.
Conversely, an excess of fertilizer creates a different kind of crisis. You intend to nourish me, but too much creates a hostile environment around my root zone. The high concentration of soluble salts in synthetic fertilizers literally pulls water out of my root cells through a process called osmosis. This is a chemical burn. It mimics drought stress but originates from a place of excess, not deficit. The brown tips from over-fertilizing often have a slight yellow or pale green halo between the dead brown tissue and the healthy green leaf. You might also see a white, crusty buildup of salt deposits on the surface of my soil or on the rim of my pot. My growth might be stunted, and other leaves could show signs of burn or unusual discoloration.
To truly understand my plight, you must look beyond the brown tips. For underwatering, my soil is your best clue. It will be dry throughout. My pot will feel light, and I will wilt dramatically, potentially recovering only slightly overnight. For over-fertilizing, the soil may actually feel damp or even waterlogged if the salt build-up has also damaged my roots' ability to absorb water. The salt crust is a definitive sign. Furthermore, underwatering typically causes issues that start at the top and outer leaves, while fertilizer burn can appear more randomly but often shows on older, lower leaves first as the salts accumulate.
Your corrective action depends on your diagnosis. If I am underwatered, please implement a consistent watering schedule. Water me deeply until it runs from the drainage holes, ensuring my entire root ball is moistened. Allow the top inch of soil to dry slightly before watering again. If I am over-fertilized, you must leach the excess salts from my soil. Place me in a sink or outdoors and slowly water me with a large volume of pure, clean water—about four times the volume of my pot—allowing it to flush completely through the soil and drain away. Repeat this process in an hour. Please refrain from feeding me again for at least a month to allow me to recover.
