From my perspective as a water lily, sunlight is my primary source of energy. My leaves are like solar panels, and the process of photosynthesis that occurs within them is what fuels my growth and, most importantly, my ability to produce those beautiful flowers you admire. When I don't receive a minimum of five to six hours of direct, unfiltered sunlight per day, my system starts to falter. The chlorophyll—the green pigment essential for capturing sunlight—begins to break down. Since I prioritize my energy for survival, I may start to reabsorb nutrients from my older, outer leaves, causing them to turn yellow. If the sunlight situation doesn't improve, the yellowing will spread to my newer leaves, and my overall growth will become stunted and weak.
Just like you, I need a balanced diet to thrive. The yellowing of my leaves, often starting with the veins remaining green while the tissue between turns yellow, is a classic sign that I'm lacking essential nutrients, particularly nitrogen, iron, or magnesium. This can happen for two main reasons. First, the soil or aquatic planting media I'm growing in might be depleted of nutrients, especially if I've been in the same pot for several years. Second, and more subtly, the chemistry of the pond water might be "locking up" the nutrients, making them unavailable for my roots to absorb. If the water's pH is too high (alkaline), I struggle to take in iron, leading to a condition called chlorosis. My roots are busy trying to feed me, but the nutrients are just out of reach.
This might sound confusing since I'm an aquatic plant, but the depth of the water above my crown (the center from which my leaves and flowers grow) is critical. If the water is too deep, my young leaves and buds have to struggle tremendously to reach the surface. This excessive effort drains my energy and can cause the new growth to turn yellow and die before it even unfurls. Conversely, if the water level drops too low, my leaves can become exposed to the air or rest on the pond liner. They are not designed for this; they can get sunburned, dry out, or become physically damaged, all of which result in yellowing and crisping. I need a stable water level that allows my leaves to float effortlessly on the surface.
As I grow, I naturally expand. My rhizome (my underground stem) spreads, and I produce more and more leaves. If I'm confined to a small planting basket, I eventually become pot-bound. My roots become a tangled mass, competing for space and the limited nutrients in the soil. This congestion creates immense stress for me. It hampers root function and reduces oxygen flow, making it difficult to transport water and nutrients effectively to my leaves. The result is often a general yellowing of the foliage, reduced flowering, and leaves that are smaller than usual. I'm simply asking for a little more room to grow.
Sometimes, the yellowing is a natural process. Older leaves, those that have been on the surface for a long time, will eventually senesce (age and die). They will turn yellow and then brown before decaying. This is normal, and you should simply remove them to keep the water clean. However, if the yellowing is accompanied by spots, holes, or a ragged appearance, it could indicate pests like water lily beetles or aphids, or a fungal disease. These organisms damage my leaf tissue, disrupting their function and causing discoloration. While I have some natural defenses, a severe infestation can overwhelm me.
