From our perspective, the most common and critical issue is a lack of adequate light. In our natural Australian habitats, we thrive under full, bright sun. As houseplants, we are often placed in locations that you perceive as "bright," but which are significantly dimmer than our needs. A north-facing window (in the Southern Hemisphere) or a south-facing window (in the Northern Hemisphere) is the absolute minimum. Without several hours of direct sunlight daily, we become etiolated—stretching weakly with sparse foliage. Our energy production plummets, weakening our entire system and making us susceptible to other problems. We simply cannot photosynthesize enough to sustain our growth and, most disappointingly, we will likely refuse to produce our beautiful, intricate flowers.
Your watering habits are a constant source of stress for our root systems. We are exceptionally sensitive to waterlogged conditions. Our roots are adapted to well-draining, often sandy or rocky soils, and they require excellent aeration. When planted in standard potting mix and subjected to frequent watering, the soil retains too much moisture. This suffocates our roots, literally drowning them as they cannot access oxygen. This leads to root rot, a fatal condition where the roots die and decay. Conversely, while we are drought-tolerant, allowing the potting medium to become bone dry for extended periods will also cause fine root death and lead to wilting, leaf browning, and drop.
The indoor environment presents a conflicting set of conditions for us. Many homes, especially during winter, have very low humidity due to heating systems. While some Grevillea species can handle dry air, low humidity can encourage spider mite infestations, which weaken us by sucking our cell contents. However, the solution is not to mist our foliage, as this can promote fungal diseases. We prefer good air circulation around our leaves, mimicking the breezy conditions of our native slopes. Stagnant, humid air is as detrimental as overly dry air. It is a delicate balance that is difficult to achieve indoors without careful placement and perhaps a small fan for gentle movement.
Our nutritional needs are highly specialized. We are known as "proteoid" plants, meaning we have evolved unique roots that are exceptionally efficient at absorbing phosphorus from nutrient-poor soils. Standard houseplant fertilizers are often far too high in phosphorus for us. When you apply them, this phosphorus becomes toxic, burning our roots and preventing us from taking up other essential micronutrients like iron and manganese. This manifests as yellowing leaves with dark green veins (chlorosis), stunted growth, and eventual death. We require a special low-phosphorus, slow-release fertilizer formulated for native plants like ourselves.
Finally, the confines of a pot and the wrong soil chemistry cause significant stress. We prefer to spread our roots. Being pot-bound too quickly can severely limit our growth and health. More critically, we require an acidic to neutral soil pH. Many municipal water sources are alkaline (hard water). Over time, watering with this water will raise the pH of the potting mix, locking up certain nutrients and making them unavailable to us, leading to deficiencies even if they are present in the soil. This, combined with the inherent challenges of a container, creates a constant uphill battle for our root systems to function properly.
