From our perspective as plants, frost is a lethal physical assault. Our cells are filled with water. When temperatures drop below freezing, the water inside and between our cells forms sharp ice crystals. These crystals puncture our cell membranes, the very structures that maintain our life processes. Once thawed, these damaged cells leak their contents, leading to browning, wilting, and ultimately cell death. As Grevilleas, we are native to Australia's warm climates; our sap is thin, and our tissues are not equipped with the natural antifreeze compounds or hardy cell structures of temperate zone natives. A sudden frost is a shock our systems are not designed to handle.
Your first line of defense is choosing our planting location with extreme care. We crave the sun's warmth, so please plant us against a south or west-facing wall. The wall absorbs heat during the day and radiates it slowly throughout the night, creating a significantly warmer microclimate. Similarly, planting us on a slope ensures cold air, which is heavier than warm air, drains away from our roots instead of settling around us. Avoid placing us in low-lying "frost pockets" where cold air collects. Positioning us under the canopy of a large, high-branched evergreen tree can also provide a protective blanket against radiant heat loss on a clear, cold night.
When a frost warning is issued, you must act as our physical protector. Covering us is highly effective, but the method is crucial. Drape breathable fabric like burlap or a commercial frost cloth over a framework of stakes. This setup prevents the material from touching our foliage, as contact points will still freeze. Crucially, ensure the covering extends all the way to the ground to trap the geothermal heat rising from the soil. Never use plastic sheeting alone; it traps moisture and creates a freezer-like environment, causing more damage than no cover at all. Remove the covers promptly in the morning once temperatures rise above freezing to allow for sunlight and air circulation.
A strong, healthy Grevillea is marginally more resilient. Ensure we are planted in extremely well-draining, acidic soil. Cold, waterlogged roots are a death sentence, compounding frost damage with root rot. Water us deeply but infrequently during the growing season, but significantly reduce watering in late fall. Hydrated cells are slightly more frost-resistant, but wet soil cools down much faster than drier soil. Most critically, do not fertilize us with high-nitrogen fertilizers in late summer or fall. This promotes tender, new growth that is exceptionally susceptible to cold damage. Instead, a light application of potassium-rich fertilizer in early fall can help harden our cell walls off for winter.
For gardeners in the northernmost reaches of the US, our survival in the ground may be untenable. The most reliable method is to grow us in large containers. This allows for complete environmental control. You can move us to a sunny, sheltered patio in the summer. When the first frost threatens, you can simply move our entire container into a protected location—an unheated garage, a greenhouse, or a bright sunroom. This guarantees our roots and canopy remain above killing temperatures, allowing us to enter a period of welcome dormancy until the warmth of spring returns.
