Grevillea, a genus of evergreen shrubs and trees native to Australia, thrives in well-drained soils and is adapted to drought-prone environments. However, improper watering—whether overwatering or underwatering—can stress the plant, leading to visible symptoms. Understanding these signs from the plant's perspective helps ensure optimal growth and health.
From the plant's viewpoint, overwatering disrupts root function and soil oxygen levels, causing physiological stress. Key signs include:
Overwatered Grevillea often exhibits yellowing leaves, particularly in older foliage. This occurs because waterlogged roots cannot absorb nutrients efficiently, leading to chlorosis (loss of green pigment). The plant prioritizes survival by sacrificing older leaves.
Soggy soil suffocates roots, promoting fungal infections like Phytophthora. The plant's roots turn brown or black, become mushy, and fail to transport water or nutrients. Above ground, the plant may wilt despite wet soil—a paradox caused by root death.
Excess moisture triggers leaf abscission (shedding) as the plant reduces transpiration to conserve energy. Younger leaves may also appear limp or swollen due to cellular damage from water absorption.
Underwatering forces the plant into survival mode, conserving water at the expense of growth. Key symptoms include:
Grevillea leaves wilt or curl inward to minimize surface area and reduce water loss through transpiration. The plant's cells lose turgor pressure, causing drooping. Prolonged drought may lead to brittle, crispy foliage.
Insufficient water slows metabolic processes, halting new shoots and flowers. The plant allocates limited resources to roots, searching for moisture, while aerial growth stagnates.
Leaf edges turn brown or crispy (necrosis) as the plant sacrifices peripheral tissues to protect vital parts. This is often accompanied by premature leaf drop to conserve water.
Grevillea's adaptations to water stress include:
In drought, roots grow deeper to access groundwater. Overwatering inhibits this adaptation, causing shallow, weak roots.
The plant closes stomata (leaf pores) to retain moisture, but this also limits photosynthesis, affecting energy production.
Some Grevillea species have fine, needle-like leaves to reduce water loss, making them more sensitive to overwatering than species with broader foliage.
To mimic the plant's natural habitat:
Grevillea prefers soil that dries slightly between waterings. Insert a finger into the soil—water only if the top 2–3 inches are dry.
Plant in sandy or loamy soil mixed with gravel to prevent water retention. Avoid heavy clay or compacted soils.
Water sparingly in winter (dormant phase) and increase slightly in summer, but always prioritize deep, infrequent watering over frequent shallow doses.
