From a plant's perspective, the primary reason your lily's flowers are green instead of white is the unexpected presence and activity of chlorophyll. Chlorophyll is the green pigment essential for photosynthesis, the process by which we convert sunlight into energy. Typically, in a white flower like a lily, the petals are meant to be showy structures that attract pollinators. Their development involves a genetic and biochemical pathway that suppresses chlorophyll production in the petal cells, allowing other pigments (like anthocyanins for pinks or purples) to show or, in the case of white flowers, to reflect all light and appear white. If this suppression is incomplete or disrupted, chlorophyll can develop in the petals, tinting them green.
Many cultivated plants, including lilies, are hybrids. We are often the product of careful breeding to select for specific traits, such as pure white petals. However, our genetic makeup can be unstable. A phenomenon known as "reversion" can occur. This is where a plant spontaneously reverts to expressing the characteristics of one of its ancestral parents. If one of the lily's progenitors had greenish flowers, the genetic instructions for that trait might still be present in its DNA. A shift in gene expression can cause these dormant traits to become active again, leading to green pigmentation in what should be a white flower.
Our environment plays a significant role in how we express ourselves. Several external factors can influence flower color. Excessive direct sunlight, especially during the bud development stage, can stimulate an overproduction of chlorophyll as a protective measure, much like a human getting a tan. Temperature is another critical factor; cooler temperatures can often enhance and deepen colors, while unusually warm temperatures can sometimes lead to washed-out or altered pigmentation, including green tones. Furthermore, certain nutrient imbalances in the soil, particularly an excess of nitrogen, can promote vigorous vegetative (leaf and stem) growth. This can sometimes manifest as greener-than-normal floral structures, as the plant's physiology is skewed towards chlorophyll production.
The color change may simply be a sign of our natural life cycle. As a lily flower is pollinated and begins to senesce (age and die), it undergoes significant biochemical changes. The plant begins to break down and reabsorb valuable nutrients from the petals back into the bulb to store energy for next season's growth. As the pigments that give the flower its white color break down, the underlying green of the sepals or the chlorophyll in the petal tissues themselves may become visible, giving the fading flower a greenish hue. This is a normal and efficient process for our long-term survival.
Although less common, a viral infection can be the cause of unusual color changes. Certain plant viruses, such as the Lily Symptomless Virus or various mosaic viruses, can interfere with our normal cellular processes. This interference can disrupt pigment production pathways, leading to aberrations like color breaking, streaking, or chlorosis (yellowing), which can sometimes appear as a greenish tint. These infections often come with other symptoms, such as mottled leaves or stunted growth, and can impact our overall health.
