From my roots upward, water is my lifeblood. When my leaves begin to turn a uniform, pale yellow, starting with the older, lower leaves, it is often a sign that I am not receiving enough water. My extensive root system requires consistent moisture, especially during hot, dry spells common in many US regions. Without it, I cannot transport essential nutrients, leading to chlorosis—the loss of the green chlorophyll I need to feed myself. Conversely, if my roots are sitting in saturated, waterlogged soil, they begin to suffocate and rot. Damaged roots cannot absorb water or nutrients at all, resulting in a similar yellowing of my leaves, though often accompanied by a wilted, mushy appearance.
My vibrant green foliage is a direct reflection of my nutritional intake. A lack of key nutrients will cause my leaves to signal distress through yellowing. A common issue is nitrogen deficiency. Nitrogen is mobile within my system, so I will prioritize sending the limited nitrogen I have to support new growth. This causes the older leaves to turn a generalized yellow first. Another frequent problem, particularly in soils west of the Mississippi, is iron chlorosis. This occurs when the soil pH is too high (alkaline), making iron unavailable to my roots. Without iron, I cannot produce chlorophyll, leading to a distinct yellowing between the veins of my newest leaves, while the veins themselves remain green.
While I thrive in full sun, the intensity of the summer sun, particularly in southern US zones, can sometimes be too much. Excessive heat and intense sunlight can scorch my leaves, causing them to yellow, brown, and become crispy, especially at the edges. This is a physiological response to prevent excessive water loss through transpiration. Furthermore, if I am planted in an area that receives too much shade, I will also protest. Without sufficient sunlight, my photosynthetic process is hampered. I may become leggy as I stretch for light, and my lower leaves may yellow and drop because they are no longer productive assets to me.
Unwelcome guests are a significant burden. Sap-sucking pests like cyclamen mites or aphids attack my tender leaves and flower buds. They pierce my tissues and drain my vital fluids, which directly damages the cells and disrupts nutrient flow, resulting in stunted, curled, and yellowed leaves. Below the soil, root-knot nematodes can infest my roots, creating galls that block water and nutrient uptake, causing a general decline and yellowing. Fungal diseases are another threat. Powdery mildew coats my leaves in a white powder, hindering photosynthesis. Crown and root rot caused by fungi like Sclerotium or Fusarium attack my base, directly compromising my entire vascular system and leading to a rapid yellowing and collapse of my stalks.
