As a plant, my existence is fundamentally driven by photosynthesis, the process of converting light energy, water, and carbon dioxide into the sugars that fuel my growth and vibrant blooms. Light is not merely a preference; it is my primary source of energy. For me, a geranium, the intensity, duration, and quality of light directly dictate my overall health, structural integrity, and reproductive success. The question of "full sun" is therefore a question of providing the optimal conditions for my most vital biological function.
From my point of view, "full sun" translates to receiving a minimum of six to eight hours of direct, unfiltered sunlight each day. This does not mean I require relentless, scorching afternoon sun from dawn until dusk, though I can often tolerate it. The ideal scenario involves basking in the strong, direct light of the morning sun, which is rich in the blue wavelengths that promote strong leaf and stem development. This ample light exposure ensures my photosynthetic factories (chloroplasts within my leaves) operate at peak efficiency, producing abundant energy.
When planted in an area that you would describe as partial shade or full shade, I must respond physiologically. My stems will begin to elongate rapidly in a desperate search for a stronger light source, a condition you call etiolation or becoming "leggy." This growth is weak and spindly, unable to robustly support my weight or future flower heads. Furthermore, my energy reserves will be prioritized for survival over reproduction. This means I will produce significantly fewer flower buds, and any existing buds may drop before opening. The vibrant green of my leaves may also fade to a paler, yellowish-green (chlorosis) due to reduced chlorophyll production.
In full sun, my growth habit becomes compact and bushy, with strong, sturdy stems and deeply colored, thick leaves. The abundant energy allows me to direct a surplus into flowering, resulting in prolific and continuous blooms throughout my growing season. However, there is an upper limit to my tolerance. In regions with extremely intense summer heat, the combined stress of maximum solar radiation and high temperatures can cause sunscald on my leaves and lead to excessive water loss through transpiration. In such environments, I greatly appreciate receiving afternoon shade, which provides respite from the most intense heat of the day while still allowing me to meet my full-sun requirements during the morning and early afternoon.
It is important to note that while most common zonal geraniums (*Pelargonium x hortorum*) thrive in the conditions described above, other members of our group have slightly adapted needs. For instance, ivy geraniums (*Pelargonium peltatum*), while still sun-loving, often perform best and maintain better flower color when protected from the most intense afternoon sun. Scented-leaved geranium varieties are also generally adaptable to full sun but can be more forgiving of light afternoon shade. The common thread remains: we all require a generous amount of direct sunlight to truly flourish.
