From a plant's perspective, dormancy is not a period of inactivity but a highly strategic survival mechanism. It is a state of arrested growth triggered by environmental cues, primarily decreasing photoperiod (shorter days) and lower temperatures. For a plant, entering dormancy is like closing the shutters on a house to conserve energy during a storm. Metabolic processes, including photosynthesis and respiration, slow down significantly. This reduces the plant's need for water and nutrients at a time when they may be scarce or difficult to absorb from cold soil. It is a crucial adaptation that allows perennial plants to survive unfavorable conditions and redirect energy to their core structures, such as roots and stems, ensuring they can burst forth with new growth when favorable conditions return.
To understand a Grevillea's winter behavior, one must consider its origins. The vast majority of Grevillea species are native to Australia, with a significant number hailing from climates that do not experience harsh, freezing winters with prolonged snow cover. Their evolutionary strategy is not built around deep winter dormancy like a deciduous tree in a northern forest. Instead, they are predominantly evergreen shrubs and trees adapted to a climate with mild winters and periods of seasonal drought. For a Grevillea, winter is not a signal to shut down completely but rather a cue to slow its growth rate. It continues to photosynthesize on milder days, though at a reduced pace due to the lower light intensity and cooler temperatures.
A Grevillea's specific response to winter is highly dependent on its local microclimate and genetic makeup. In its native habitat or in regions with very mild winters (USDA zones 9-11), a Grevillea may show almost no signs of dormancy and could even continue flowering sporadically throughout the cooler months. However, when planted in areas that experience frosts or consistent cold snaps, the plant will adopt a more pronounced state of quiescence. Growth will visibly halt, and it will not produce new leaves or flowers. The plant is not dormant in the classical sense but is instead in a holding pattern, waiting for the soil and air to warm. It is still alive and maintaining its systems, just at a much slower rate. A hard freeze can damage tender new growth, so this slowdown is a protective measure.
It is vital from the plant's viewpoint to distinguish between a healthy seasonal slowdown and a negative stress response. A Grevillea slowing its growth in cooler weather is normal and healthy. However, if the plant is exposed to temperatures far below its tolerance level (which varies by species but is often around 25-30°F / -4 to -1°C), the response is not dormancy but damage. Leaf burn, browning tips, and dieback are signs of cold injury, where plant cells have frozen and ruptured. Similarly, cold, waterlogged soil can lead to root rot, as the slowed metabolic rate makes it difficult for the plant to manage excess moisture around its roots. Therefore, what might appear as dormancy could sometimes be the plant struggling to survive an abiotic stressor it is not fully adapted to withstand.
