Wilting in a chrysanthemum is a distress signal indicating a disruption in the plant’s ability to move water from the roots to the leaves. This symptom is common and often points to a treatable issue. A careful diagnosis is necessary because wilting can be caused by problems ranging from soil moisture issues to more serious underlying diseases or pests. This guide provides a systematic approach for home gardeners to identify the specific cause of their plant’s wilting.
Diagnosing Water-Related Stress
Water problems are the most frequent cause of wilting in garden plants, but the symptoms of underwatering and overwatering can be surprisingly similar above ground. The first step in diagnosis is to evaluate the soil moisture by inserting a finger about two inches deep into the soil.
If the soil feels dry, crumbly, and light, the plant is likely suffering from underwatering. In this scenario, the leaf edges may appear slightly crispy, and the wilting should resolve quickly after a deep watering. However, if the soil is consistently soggy, heavy, and cool to the touch, the wilting is a symptom of overwatering, which is a far more serious problem.
Excess water displaces oxygen in the soil, creating an anaerobic environment that suffocates the roots and promotes the growth of water mold pathogens like Pythium. This condition is known as root rot, where damaged, mushy, black roots cannot absorb water, causing the plant to wilt despite the surrounding moisture. Overwatered leaves will often feel soft and limp, and the lower leaves may turn yellow and drop off. Wilting caused by root rot will not improve after watering, unlike simple drought wilting.
Pests and Fungal Infections
If the soil moisture seems balanced, the wilting may be caused by biological invaders that directly interfere with the plant’s internal systems. A close visual inspection of the underside of the leaves and the stems, particularly on new growth, can reveal the presence of common sap-sucking pests.
Aphids are small, soft-bodied insects that cluster on new shoots and leaf undersides, extracting plant sap and causing leaves to curl, yellow, and wilt. Their presence often leaves behind a sticky residue called honeydew, which encourages the growth of black sooty mold. Another common issue is spider mites, tiny arachnids that cause fine, pale stippling or a dusty look on the leaves as they feed. Severe infestations are identifiable by fine webbing near buds and stems, and the wilting is often accompanied by bronze or reddish discoloration of the foliage.
Fungal diseases are more insidious because they operate internally, blocking the plant’s water transportation system. Fusarium wilt, caused by the soil-borne fungus Fusarium oxysporum, is a common culprit in chrysanthemums. This disease often causes wilting and yellowing that begins on the lower leaves and may affect only one side or section of the plant initially. Cutting open a stem may reveal reddish-brown discoloration or streaking in the vascular tissue, indicating the fungus has clogged the water pathways.
Environmental Shock and Heat Stress
Wilting can also be a temporary, non-biological response to sudden changes in the plant’s surrounding environment. Heat stress occurs when the rate of water loss through transpiration exceeds the rate of water uptake by the roots. This is common during intense afternoon sun or reflected heat. This type of wilting reduces the surface area of the leaves exposed to the sun to conserve moisture. It is a temporary condition, with the plant recovering and the leaves becoming firm again once temperatures cool down, often in the evening.
If the mum was recently moved, repotted, or planted, it may be experiencing transplant shock. Even with gentle handling, some of the roots are damaged or lost during the transition. This temporary inability to absorb sufficient water leads to wilting and possibly leaf yellowing until the root system has time to re-establish itself in the new soil.
Sudden, significant drops in temperature, especially cold snaps early in the season, can also cause a form of environmental shock. While chrysanthemums are hardy, a rapid exposure to near-freezing temperatures can damage the cell structure, leading to leaf collapse and wilting that looks similar to drought damage. In these cases, the wilting is not due to a lack of water but to the physical injury caused by the thermal change.