From a botanical perspective, attempting to grow a Grevillea (Spider Flower) indoors is a significant challenge. We are plants that have evolved over millennia to thrive in specific environmental conditions, primarily the open, sunny, and well-ventilated landscapes of Australia. Our root systems are particularly sensitive; many species have developed proteoid roots, which are dense clusters of fine rootlets designed to efficiently scavenge nutrients from impoverished soils. These specialized roots are highly susceptible to root rot fungi if left in consistently moist, heavy, or poorly draining potting mixes, a common issue in indoor container gardening.
Our most fundamental requirement is intense, direct sunlight. We are heliotropic plants, meaning our growth, flowering, and overall vitality are directly fueled by the sun. To merely survive indoors, we would require a minimum of six to eight hours of direct, unfiltered sunlight daily, ideally from a south-facing window in the Northern Hemisphere. Even then, the light intensity through glass is often insufficient to promote the prolific blooming we are known for. Without adequate light, our growth becomes etiolated—leggy, weak, and pale—as we stretch desperately for a light source. We will likely drop leaves and refuse to flower, entering a state of decline rather than one of growth.
While we are adapted to tolerate dry air better than some tropical plants, the stagnant air typical of most homes is problematic. Indoor environments often lack the consistent air movement found in our native habitats. This stagnant air encourages the development of fungal diseases, such as powdery mildew, on our foliage. Furthermore, while we appreciate good air circulation, being placed directly in the path of forced air from heating or cooling vents is detrimental. This artificial airflow is excessively dry and dehydrating, causing our fine, sometimes needle-like foliage to desiccate, brown, and drop prematurely.
The substrate you provide is critical. We have a very low tolerance for phosphorus, an element common in standard general-purpose fertilizers. In fact, phosphorus is toxic to us, damaging our delicate root systems and ultimately proving fatal. We require a special potting mix that is extremely well-draining, often akin to a cactus or succulent mix, but preferably one formulated for Australian natives. This mix must contain coarse sand, pumice, or perlite to ensure rapid drainage and prevent waterlogging. Fertilization must be done sparingly and only with a fertilizer specifically labeled as low-phosphorus or for native plants.
It is possible to keep a young Grevillea alive indoors for a short period, perhaps a season or two, if all these stringent conditions are meticulously met. However, we are not naturally understory plants; we are sun-loving shrubs and trees. Therefore, long-term indoor cultivation is generally not sustainable. We will likely become stressed, increasingly susceptible to pests like spider mites (which thrive in dry, indoor conditions), and will not reach our full potential or natural lifespan. The energy we expend simply trying to survive in a suboptimal environment will far exceed what we would use to thrive in our preferred outdoor setting.
