Beginner Gardening: Orange growth on underside of Hollyhocks leaves (nasty!), 0 by plantenthusiast

plantenthusiast wrote:
Bev,

I hate to tell you this, but what you are seeing is called rust. It is a rampant fungal disease that is notorious for affecting Hollyhocks. The best way to avoid it is to contain the spread, and keep those Hollyhocks (foliage) dry as a bone!

There are various forms of anti fungal treatments, such as sulphur, but quite frankly, it is really tough to get rid of rust on a plant once it's got it.

The seeds will not be affected by the disease, but the spores can live in the ground in the surrounding area, and infect new plants. There are various plants that are also hosts to the type of rust that affects Hollyhocks, and it can be spread this way too. Various types of plants can be affected by Hollyhock rust, so like I mentioned previously, you will definitely want to control the spread. The Hollyhocks are likely to be affected the worst. You were wise to trash the affected leaves; a lot of people trash the entire plants that are infected with rust. Whatever you do, don't compost them! You can leave them to continue growing, but if you do, you may want to consider choosing a different location to seed next year's plants. Give it a try though, you never know; if you keep next year's plants in the same place, and are able to keep them dry, they just might not be affected by it.

Sorry to be the bearer of bad news; there are very few climates in which Hollyhocks can be grown rust free. Good luck with those Hollyhocks,

-Plantenthusiast

Below is an example of rust on Hollyhocks; it can vary a bit in appearance though.