I grew the plants from seed and planted them against my porch because they grow very tall. They grew well and quickly. About the middle of July I started noticing some spots on the leaves but the plants still seemed healthy. Then we had a of couple weeks of hot humid weather in August and BAM!, my hollyhocks were covered in orange and yellow pustules and the edges of the leaves were grey and curly. What happened?
Now, if I had done my research on this plant, I'm not sure I would have planted it. Hollyhocks are prone to Hollyhock Rust (Puccinia malvacearum). In fact, they are so prone to it, it is pretty much a given they will get it every year. Hollyhock rust is a fungal disease which is spread by airborne spores. It also affects any plants in the Malva family, abutilon, hibiscus, lavatera, malvastrum and sidalcea, so if any one in the area is growing any of these plants, their spores can infect your plants and vice versa. The spots on the upper leaf and the pustules on the under leaf develop until the leaves turn to ash and the spores are released.
Hollyhock rust likes hot, wet conditions. Our hot and humid New England summers are a perfect breeding ground for it. English summers can be hot but without the humidity. My guess is it is easier to control under those conditions. I didn't stand a chance, but if I had been on the look out for it I would have been more careful with my watering and plant spacing and would have removed infected leaves as soon as I saw them. You can help to control it by cutting the plants to the ground in the fall and properly disposing of the plant material in the trash. The fungus can lie dormant in seemingly healthy leaves.
If I was willing to use chemicals I could heavily treat the plants twice a week all summer long with a fungicide but I'm not going to do that.
|I can't believe how quickly these plants went down hill.|