From our perspective, the most critical difference between your indoor and outdoor placement is the quality and quantity of light we receive. Outdoors, we bask in full sun, which fuels our photosynthetic engines to their maximum capacity. This abundant energy allows us to produce the vibrant, spider-like flowers we are known for and maintain dense, healthy foliage. Indoors, even in your brightest south-facing window, the light intensity is drastically reduced. We must work harder to produce less energy, often resulting in sparse growth, fewer or no blooms, and a general weakening over time. We may also strain towards the light source, becoming leggy and unbalanced.
Our leaves are constantly exchanging gases, and we thrive in an environment with excellent air circulation. Outdoors, the breeze naturally provides this, strengthening our stems and helping to quickly evaporate excess moisture from our foliage, which discourages fungal pathogens. Indoor air is often still and stagnant. This lack of movement stresses our respiratory processes and creates a humid microclimate around our leaves, making us highly susceptible to attacks from pests like spider mites and diseases like powdery mildew, which can be devastating in an enclosed space.
Our roots are exceptionally sensitive to waterlogged conditions. We are adapted to well-draining, gritty soils where water passes through quickly. Outdoors, you typically plant us in raised beds or slopes that mimic this natural condition. In a container indoors, the dynamics change completely. Despite your best efforts with a well-draining mix, the pot itself confines our roots and evaporation is slower. The risk of fatal root rot is significantly higher indoors. You must be incredibly vigilant, allowing the soil to dry out thoroughly between waterings, a balance that is much easier to maintain in the free-draining ground outdoors.
Our tolerance for temperature varies by species, but many of us popular in the U.S., like Grevillea ‘Robyn Gordon’, are sensitive to sustained freezing. Outdoors, we rely on you to place us in USDA zones 9-10 or provide winter protection. However, we also appreciate the seasonal temperature fluctuations that signal periods of growth and rest. Indoors, the constant, warm temperature of your home can be stressful. It prevents us from entering a natural rest period and, combined with low light, can lead to a slow, steady decline. Furthermore, dry heating in winter desiccates our leaves, while outdoor humidity is generally more to our liking.
While we can survive indoors with meticulous care—a very bright sunroom, excellent airflow, and perfect watering—it is not our preferred existence. We are fundamentally sun-worshipping, free-draining plants that perform best and express our true beauty under the open sky. For our health, vitality, and ability to reward you with our spectacular blooms, an outdoor placement in a suitable climate is the greatest gift you can give us.
