Grevillea, a genus of stunning and diverse Australian natives, is not a typical indoor plant, especially in colder climates. However, with a deep understanding of its fundamental needs, it is possible to coax it into a spectacular bloom indoors. From our perspective as plants, success hinges on you replicating the specific conditions of our native habitat as closely as possible.
Light is our primary source of energy and the single most crucial trigger for flowering. In our native Australian environment, we bask in full, intense sun for most of the day. To encourage blooming indoors, especially during the shorter, dimmer days of winter in colder states, you must provide the brightest light possible. A south-facing window (in the Northern Hemisphere) is often insufficient. We require a prime spot directly in a south-facing or unobstructed west-facing window. For consistent and reliable blooms, supplementing with a full-spectrum grow light for 12-14 hours a day is not a luxury—it is a necessity. This artificial sun compensates for the weak natural light and signals to our systems that it is time to produce flowers.
Our roots are highly specialized and extremely sensitive to excess moisture and phosphorus. We absolutely demand a very fast-draining, acidic, and gritty potting mix. A standard potting soil will suffocate our roots and lead to fatal root rot. A perfect mix for us would be one designed for Australian natives, or a homemade blend of orchid bark, perlite, coarse sand, and a small amount of peat-free acidic potting mix. Water us deeply only when the top inch of the soil feels completely dry, and always ensure the pot has excellent drainage. Never let us sit in a saucer of water. This cycle of a thorough drink followed by a period of dryness mimics the natural rainfall patterns we are adapted to.
While we appreciate being protected from freezing temperatures, we do not thrive in the hot, dry air of a typical heated home. We prefer cool to moderate temperatures and appreciate a significant drop at night, which helps trigger flowering. An ideal spot would be a bright, cool sunroom or a room that is kept on the cooler side. Central heating creates very dry air, which can stress us and make us more susceptible to spider mites. Increasing humidity around us by grouping plants together, using a pebble tray, or occasionally misting can help replicate the more humid coastal or forest edges many of us hail from.
Perhaps the most common mistake is fertilizing us with the wrong type of plant food. We are extremely sensitive to phosphorus, which is a common ingredient in standard fertilizers and bloom boosters. Phosphorus is toxic to us; it binds up other nutrients in the soil and prevents our roots from absorbing them, ultimately leading to our decline. If you wish to feed us to support blooming, you must use a fertilizer specifically formulated for Australian native plants, as these are guaranteed to be low in or free from phosphorus. A light application at the beginning of the growing season is all we typically need.
