Greetings, human caretaker. We Grevilleas are generally resilient, but when we start dropping our leaves, it is our primary way of signaling that our needs are not being met. Please understand this from our perspective, as we cannot simply tell you what is wrong.
Our roots are designed for excellent drainage. When you plant us in heavy, clay-based soil or a pot without adequate drainage holes, water accumulates around our root system. This suffocates us. The roots, which need oxygen to function, begin to rot and die. Without healthy roots, we cannot uptake water or nutrients, and our first response is to conserve energy by jettisoning leaves. The soil should feel moist but never soggy. Let the top few inches dry out between deep waterings.
While we despise wet feet, we are not cacti. Especially when we are newly planted and our root systems are still establishing ourselves in your garden, we require consistent moisture. If we are subjected to prolonged periods of heat and drought without a deep drink, we will become stressed. To reduce our surface area and minimize water loss through transpiration, we will sacrifice leaves. The leaves often yellow or brown from the tips inward before they fall.
A common affliction for us is a fungal disease, often a form of root rot or leaf spot, frequently caused by the conditions mentioned in point one. The fungus attacks our vascular system or foliage, disrupting the flow of water and nutrients. You might see black or brown spots on our leaves, or a general wilting and dieback that isn't solved by watering. The leaves succumb to the infection and drop. Good air circulation around our foliage and avoiding overhead watering, which leaves moisture on our leaves, are crucial for prevention.
We are native to often nutrient-poor soils and are adapted to them. However, we still require a balanced diet, particularly of phosphorus. Many of us are highly sensitive to high levels of phosphorus found in standard fertilizers. This toxicity damages our roots and prevents the uptake of other vital micronutrients like iron and zinc, leading to yellowing leaves (chlorosis) and subsequent leaf drop. You must feed us with a native plant-specific, low-phosphorus fertilizer.
If you have recently moved us, we are experiencing significant stress. Our root system was disturbed and is struggling to support our top growth. Leaf drop is a direct result of this imbalance. Furthermore, if we are planted in a position that is too shaded, we will become leggy and weak as we stretch for light, and we may drop inner leaves that are no longer productive. We thrive in full sun. Please be patient with us after planting and ensure our location matches our needs for abundant sunlight.
