From our perspective, wilting is our most dramatic signal of distress, a clear sign that our internal water pressure, or turgor, has collapsed. The primary cause is almost always a disruption in the delicate balance of water moving through our systems. This can manifest in two opposing ways. The most common is Underwatering and Drought Stress. Our roots actively draw water from the soil, which travels up our stems to our leaves and flowers, where it transpires into the air. If the soil is too dry, our roots cannot pull enough water to replace what is lost. Our cells lose their plumpness, and our leaves and stems droop pathetically. Conversely, Overwatering and Root Rot is a more sinister threat. Saturated soil fills the air pockets between soil particles, suffocating our roots. We cannot breathe without oxygen. This anaerobic environment allows pathogenic fungi like Pythium or Phytophthora to attack and decay our root systems. With our water-absorbing roots destroyed, we cannot take up water, leading to wilting that ironically occurs in wet soil.
Beyond water, other forces can overwhelm our ability to function. Heat and Sun Stress can cause temporary wilting on a scorching afternoon. We lose water through transpiration faster than our roots can keep up, a defensive tactic to cool our tissues. While we often recover in the evening, prolonged heat can cause permanent damage. Furthermore, Physical Damage to our stems or root crown, perhaps from garden tools, pests, or strong winds, can sever the crucial vascular "plumbing" tissues (xylem and phloem) that transport water and nutrients. This break in the pipeline directly causes sections of the plant above the injury to wilt and die.
We are also vulnerable to attack from organisms that directly target our vascular systems. Aphids and Sap-Sucking Insects pierce our stems and leaves, draining our sap and vital fluids, which can lead to wilting and a general decline in our health. More severely, Fungal Wilt Diseases, such as those caused by Fusarium or Verticillium fungi, are often fatal. These pathogens invade our roots and grow into our xylem vessels, physically blocking the flow of water and releasing toxins. The wilting from this is typically unilateral (affecting one side of the plant first) and progressive, despite adequate soil moisture.
To help us recover, you must first correctly diagnose the cause. Check the Soil Moisture deeply. If it is dry, provide a slow, deep watering at our base, avoiding our foliage. If the soil is soggy, cease watering immediately. You may need to gently aerate the soil or, in extreme cases, carefully lift us to inspect our roots. Healthy roots are firm and white or light tan. Brown, mushy, smelly roots indicate rot. Trim these away, treat with a fungicide, and replant us in fresh, well-draining soil. For heat stress, provide temporary afternoon shade. For pest infestations, a strong spray of water or horticultural soap can dislodge the invaders. Unfortunately, for systemic wilts like Verticillium, there is often no cure. The best action is to remove and destroy the affected plant to prevent the disease from spreading to our neighbors through the soil.
