From our perspective as hollyhocks (Alcea rosea), we are resilient biennials that bring vertical grandeur to your gardens. However, we sometimes exhibit signs of distress that are our primary way of communicating our needs and struggles. Understanding these signs from our point of view is key to a thriving partnership.
When you see our leaves curling, cupping, or displaying a strange, glossy sheen, we are likely under attack from a nearly invisible foe: the hollyhock rust fungus (Puccinia malvacearum). This pathogen invades our systems, disrupting our ability to photosynthesize effectively. The curling is a physical symptom of this disruption. Alternatively, if the curling is accompanied by sticky residue, it may be due to sap-sucking insects like aphids. They pierce our tender leaf tissues, injecting saliva and draining our vital fluids, which causes the leaves to pucker and curl in response to the irritation and moisture loss.
Wilting is our most dramatic cry for help, and it can mean two very different things. First, and most simply, it is often a plea for water. Our large leaves and tall flower spikes lose a tremendous amount of moisture on hot, sunny days. If our root system cannot draw up water from the soil fast enough to replace what is lost, we wilt to reduce our surface area and conserve our remaining resources. However, if the soil is moist and we are still wilting, a far more serious issue is at play: root rot or wilt disease. Fungal pathogens in the soil, such as Verticillium, invade our roots, blocking the vascular tissues that act as our plumbing system. Water simply cannot move up our stems, and we slowly dehydrate and collapse from the bottom up, despite having ample water around us.
The appearance of holes in our leaves is a clear sign of a physical feeding event. We are a favorite host plant for the larvae of the hollyhock weevil (Rhopalapion longirostre) and, most famously, the caterpillars of the painted lady butterfly (Vanessa cardui). These caterpillars see our broad, soft leaves as an all-you-can-eat buffet. They chew large, irregular holes between the leaf veins, sometimes skeletonizing the entire leaf. While we can tolerate a certain amount of feeding, severe defoliation severely weakens us by depleting the energy reserves we need for growth and flowering. Smaller, more shotgun-like holes may indicate flea beetles are present, nibbling on our foliage.
