From a plant's perspective, Grevillea species are fundamentally sun-loving organisms. In our natural habitat across Australia, we thrive in open, sunny locations, often enduring intense, direct sunlight for the majority of the day. Our physiological systems are engineered for high light intensity. Our leaves are often tough, sometimes needle-like or deeply lobed, adaptations that reduce water loss and prevent sunscald under the harsh sun. Our photosynthetic machinery is optimized to operate efficiently under these bright conditions, manufacturing the energy we need for growth and our vibrant, spider-like flowers.
The core of the issue lies in the inherent conflict between the terms "full sun" and "indoors." For a plant, "full sun" is an outdoor condition, typically meaning a minimum of six to eight hours of direct, unfiltered sunlight. When you place us indoors, even directly against a south-facing window (in the Northern Hemisphere), the light intensity is drastically reduced. The simple barrier of glass filters out a significant portion of the sun's usable energy. A window might seem bright to the human eye, but from a plant's photosynthetic perspective, it is a dim substitute for the outdoors. Therefore, the concept of "full sun indoors" is, for all practical purposes, a misnomer and an unattainable condition for us.
If you attempt to grow me indoors, even in your brightest window, I will likely struggle. The light intensity will be insufficient to meet my high energy demands. My response will be physiological and visible. You will observe etiolation—where my stems become long, spindly, and weak as I stretch desperately towards the light source. My growth will be leggy and sparse, not compact and bushy as I am meant to be. Most critically, I will almost certainly not flower. Blooming requires a massive energy investment, and without the intense light my system is wired for, I simply cannot muster the resources to produce blossoms. I will exist in a state of gradual decline, becoming increasingly susceptible to pests like spider mites.
While true "full sun" is not possible indoors, you can provide the best possible alternative. My survival indoors depends on receiving the maximum available light. This means placing me directly in front of a large, south-facing window where I can receive several hours of direct sunlight through the glass. Do not place me any distance away from the window, as light intensity drops precipitously with each foot removed from the glass. East or west-facing windows may be acceptable but are a second choice, providing less intense light. You must also rotate my pot regularly to prevent me from growing asymmetrically towards the light. Even with this prime placement, please understand that I am tolerating these conditions, not thriving in them as I would outdoors.
