Neglecting clematis care in May can result in tangled growth, reduced airflow, and fewer flowers during the summer. Pests like slugs and aphids can damage young shoots, while fungal diseases such as clematis wilt may cause stems to blacken and collapse. These issues are particularly problematic for large-flowered hybrid varieties. Without proper watering and feeding, plants may struggle to cope with rising temperatures, leading to stress and diminished growth. Ensuring timely intervention can mitigate these risks and promote a thriving garden display.