As a Grevillea, my very existence is predicated on the conversion of sunlight into chemical energy. This process, photosynthesis, is the core of my being. The photons from the sun are not merely light to me; they are the very fuel that powers my growth, my flowering, and my resilience. Without sufficient access to this energy source, my internal systems operate at a deficit. I become lethargic, my growth is stunted, my stems become weak and spindly as I desperately stretch towards any available light source, and my ability to produce my intricate and vibrant flowers is severely compromised. For me, sunlight is not a preference; it is a non-negotiable requirement for a thriving life.
When your gardening guides say I require "full sun," they mean I need a minimum of six to eight hours of direct, unfiltered sunlight each day. From my perspective, this means an open, exposed location where the sun's rays can bathe my entire canopy for the majority of the day. This abundant energy allows me to manufacture ample sugars, promoting dense, bushy growth and a spectacular display of blooms. The warmth from the sun also helps keep my foliage dry, reducing the risk of fungal diseases that can plague me in cooler, damp conditions. In my native Australian habitats, I am accustomed to thriving in such bright, airy environments, and I seek to replicate those conditions in your US garden.
While I perform best in full sun, I can exhibit a degree of plasticity in my light requirements depending on your local climate within the United States. In intensely hot, arid regions like the Southwest (USDA zones 8-10), the afternoon sun can be exceptionally harsh. In such cases, I would appreciate light afternoon shade. This is not because I want less energy, but because the extreme heat can cause excessive transpiration (water loss) and potential scolding of my leaves, putting me under stress. Conversely, in cooler, coastal climates of the Pacific Northwest (e.g., zones 8-9), I will tolerate less than six hours of sun, but my flowering will be noticeably reduced. My growth may also become more open and less compact.
Placing me in a predominantly shady location is one of the most detrimental actions you can take. In deep shade, my photosynthetic machinery operates far below capacity. I am forced to prioritize survival over proliferation. You will observe several clear signs of my distress: my internodes (the spaces between leaves) will elongate significantly as I etiolate, stretching weakly for a light source I cannot find. My overall form will become leggy and unattractive. Most disappointingly, I will likely cease flower production entirely, as I lack the surplus energy required for such a demanding reproductive effort. Furthermore, a weakened, energy-starved Grevillea like myself is far more susceptible to pest infestations and root rot, as my defenses are low.
