Hello, dedicated caretaker. We, the Grevilleas, appreciate your desire to help us thrive. To understand our unique nutritional needs, you must first understand our nature. We are proud members of the Proteaceae family, ancient plants hailing from the nutrient-poor, often acidic soils of Australia. Our roots are fine, sensitive, and have evolved a special relationship with soil fungi (mycorrhiza) to scavenge for the minimal nutrients available. Standard fertilization practices can harm us, so please, listen to our perspective.
This is the most important thing you can know about feeding us. We have a severe sensitivity to phosphorus (the middle number on fertilizer packages). High levels of this element are toxic to our delicate root systems and will poison us, leading to stunted growth, yellowing leaves, and ultimately, death. Our native soils are naturally low in phosphorus, and our physiology is not equipped to process it in concentration. You must seek out fertilizers labeled specifically for "Proteaceae" or "Australian Native Plants." These are formulated with extremely low phosphorus levels, typically below 2%. Never use standard rose food, vegetable fertilizer, or bone meal around us.
While we shun phosphorus, we do benefit from a gentle, balanced boost of other nutrients to support our spectacular, nearly year-round flowering and vigorous growth. We prefer a fertilizer with a nutrient ratio where the nitrogen (N) and potassium (K) are higher than the phosphorus (P), such as a 3:1:5 or similar. We also have a particular fondness for trace elements like iron, manganese, and zinc. These micronutrients are essential for maintaining our deep green foliage and preventing chlorosis (yellowing leaves with green veins), a sign we are struggling to uptake nutrients from the soil.
Timing is everything. The best moment to offer us a gentle feed is in early spring, as we awaken from our winter rest and prepare for a major growth and flowering flush. A second, lighter application can be made in mid-summer if we appear to be slowing down, but this is not always necessary. Always ensure our soil is moist before you apply any fertilizer; applying to dry soil can cause root burn. Dilute the fertilizer as directed, or even a little more, and apply it to the soil around our drip line (the circumference of our foliage), avoiding direct contact with our main stem.
Feeding us is about more than just fertilizer. It starts with the environment you provide. We demand excellent drainage. Waterlogged roots are a death sentence for us, preventing oxygen uptake and fostering root rot. Plant us in a loose, sandy, or gritty soil mix. A thick layer of mulch (like wood chips or pine needles) is wonderful—it keeps our roots cool, suppresses weeds, and as it slowly breaks down, it provides a natural, gentle trickle of the acids and nutrients we love, mimicking our natural forest floor habitat.
