As an established Grevillea, my relationship with water is a delicate dance. I am a proud member of the Proteaceae family, hailing from the ancient, nutrient-poor soils of Australia. My very being is engineered for resilience and survival in harsh conditions. To understand how often you should water me, you must first understand my nature. My roots are not like those of a thirsty lawn or a tropical hibiscus; they are specialized, sensitive, and fiercely independent. Overwatering is not merely an inconvenience for me—it is a death sentence.
The key to watering me correctly lies beneath the soil. I have developed two types of root systems to thrive. First, I possess a deep taproot that seeks out groundwater, allowing me to access moisture far below the surface during dry spells. Second, and most critically, I have a dense mat of proteoid roots, also known as cluster roots. These are fine, hair-like roots that form a mat just below the soil surface. Their purpose is to chemically mine the soil for scarce nutrients like phosphorus and nitrogen. These proteoid roots are incredibly efficient, but they are also highly susceptible to fungal diseases like Phytophthora, which thrive in constantly moist, poorly drained soil. When you water me too often, you drown and rot these vital lifelines, effectively starving me of both water and nutrients.
An "established" Grevillea is one that has fully settled into its new home, typically after the first 6 to 12 months in the ground. During my initial establishment period, I needed regular, deep watering to encourage my roots to grow downward. Now that I am established, my extensive root network is self-sufficient. I no longer need you to provide frequent sips of water. My goal is to rely primarily on natural rainfall. Your supplemental watering should be seen as emergency relief during periods of significant environmental stress, not a routine part of my care.
Therefore, the most accurate answer to "how often" is: infrequently, but deeply. Do not adhere to a fixed weekly schedule. Instead, you must learn to read the signs from me and my environment. The correct time to water is when the top few inches of soil are completely dry. You can check this by simply pushing your finger into the soil near my base. When you do water, do so slowly and deeply, allowing the moisture to penetrate the soil profile to a depth of at least 15-20 centimeters. This encourages my deep roots to remain active and strong. A long, slow soak once every 3 to 4 weeks during a complete absence of summer rain is often more than sufficient. In cooler, wetter months, I may not need any supplemental water at all.
Several external factors will affect how quickly I use the available water in my soil. You must observe these conditions closely. If I am planted in fast-draining, sandy soil, I will dry out faster than if I am in a heavier clay-loam. During periods of intense heat, strong, drying winds, or a prolonged heatwave with no rain, my soil will desiccate more quickly. A large, mature Grevillea in full sun will have greater water demands than a smaller, younger specimen or one planted in partial shade. A thick layer of gravel or coarse mulch around my base (keeping it away from my main stem) is immensely beneficial. It helps regulate soil temperature, suppresses weeds, and most importantly, reduces surface evaporation, conserving the precious moisture that is already in the ground.
