From our perspective, not all Grevillea species are created equal when it comes to cold. Our genetic makeup determines our baseline hardiness. Some of us, like Grevillea rosmarinifolia or Grevillea ‘Canberra Gem’, have evolved to withstand colder temperatures and light frosts, while more tropical species like Grevillea robusta are far more susceptible to damage. The first step in protection is knowing your specific type's limits. Damage typically occurs when ice crystals form inside our cells, rupturing them and causing the blackened, wilted appearance you see. Young, tender new growth is always the most vulnerable, as it hasn't had time to harden off.
Our best defense against cold starts long before the first frost, with where you choose to plant us. We thrive in positions that mimic our native Australian conditions. Planting us on a slight slope ensures cold air, which is heavier than warm air, can drain away rather than settling around our roots. A location against a north or west-facing wall is ideal, as the wall absorbs heat during the day and radiates it slowly throughout the night, creating a warmer microclimate. Avoid planting us in low-lying frost pockets or areas exposed to biting easterly winds, which can accelerate freezing and cause desiccation.
Protecting our roots is paramount, as a healthy root system is our lifeline for recovery. Applying a thick, dry layer of mulch (like straw, bark chips, or dry leaves) around our base acts like a blanket, insulating the soil and preventing it from freezing solid. However, ensure the mulch is not piled against our main stem, as this can encourage rot. Crucially, our water needs change in cold weather. While it's important we are not drought-stressed entering a cold period, waterlogged soil is extremely dangerous. Soggy, cold roots are far more likely to succumb to rot and freeze damage than roots in well-drained, slightly drier soil.
When a severe frost is forecast, we benefit greatly from direct coverings. The goal is to trap the heat radiating from the ground around us. Drape breathable fabric like frost cloth, burlap, or even an old sheet over our canopy before nightfall. Avoid using plastic sheeting directly on our foliage, as it can magnify cold damage and prevent respiration. For smaller specimens, creating a simple frame to hold the material off our leaves is even more effective. Remember to remove these coverings once the temperature rises above freezing the next morning to allow for light absorption and air circulation.
If we do sustain cold damage, your patience and correct care are vital for our recovery. Resist the urge to prune away the damaged growth immediately after the frost. Those blackened leaves and stems, while unsightly, actually serve as an insulating layer to protect the inner wood from further damage in subsequent frosts. Wait until the last frost of the season has definitely passed and you see new growth beginning to sprout further down the stems. Then, you can carefully prune back to just above these new growing points. This gives us the best chance to regenerate from the living tissue.
