Grevillea bushes, native to Australia, are prized for their unique, spider-like flowers and evergreen foliage. As a plant, our watering needs are not dictated by a fixed calendar schedule but by a complex interplay of environmental factors and our own physiological state. The goal is to mimic the well-drained, infrequent but deep watering conditions of our natural habitat to avoid the root rot that is our greatest threat.
From our root's perspective, the most crucial rule is deep, infrequent watering. A light daily sprinkle is detrimental; it encourages our roots to stay shallow at the surface, where they are vulnerable to heat and drought stress. Instead, a slow, deep soak encourages our root system to grow downward, seeking moisture and creating a more resilient, stable, and drought-tolerant plant. Water us until the soil is moist at a depth of 6-8 inches, then allow the top several inches of soil to dry out completely before watering again. We will signal our thirst not with wilted leaves (a late sign) but with a slight loss of leaf sheen or a less firm feel to our newer growth.
In these climates, characterized by intense sun, high heat, and low humidity, our primary demand is for establishment. For our first full growing season, we require weekly deep watering to develop our extensive root system. Once established, we are remarkably drought-tolerant. During the peak of summer, a deep soak every 2-3 weeks is typically sufficient. The winter rainy season often provides enough moisture that supplemental watering is unnecessary. The key for us here is impeccable drainage; planting on a mound or in a raised bed is often essential to prevent water from pooling around our crown during a rare heavy rain.
This climate, with its wet winters and long, dry summers, closely mirrors our native Australian environment. It is where we feel most at home. The schedule is straightforward: deep watering is essential from late spring through early fall. During this period, a deep soak every 3-4 weeks will sustain us. We rely almost entirely on winter rains from late fall through early spring and should not be watered during this cool, damp period. Overhead watering in cool weather is a direct invitation for fungal pathogens to attack our foliage and roots.
Here, the challenge for us is not drought but excessive ambient moisture and summer rainfall. Our main request is to be planted in the fastest-draining soil possible, amended heavily with sand and grit. Watering must be highly conservative. Often, natural rainfall will meet our needs. Only water us during extended periods of summer drought (more than 2 weeks without rain) or if we are container-grown. In these regions, vigilance against root rot due to waterlogged soil is a constant requirement for our survival.
When our roots are confined to a pot, we lose our ability to seek out deep moisture reserves. We dry out much faster than our in-ground counterparts, especially in warm, windy conditions. You must check our soil moisture frequently by feeling the soil several inches down. Water us deeply when the top few inches are dry, ensuring water flows freely from the drainage holes. However, the pot must never be left sitting in a saucer of water. The cycle will be much more frequent, potentially weekly in summer, but always guided by the soil's dryness, not the day of the week.
