Orange growth on underside of Hollyhocks leaves (nasty!)

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whozzat08 Houston, TX(Zone 9a) Apr 07, 2008

I have two plants that came up from last year. They both are about 4 ft. and getting ready to bud. They are in the ground, with potted plants surrounding them.
I have been fighting aphids(Black? the ones on my hibiscus and roses were green) on my Rose of Sharon with Dawn solution and blasting with the hose. It has worked so far on the aphids? but I think all that water twice a day on the hollyhock was not a good thing.

It is like a orange mold or mildew growing on the underside of the bottom leaves. I striped off all the leaves that it was growing on, and they went out in todays trash so I can't get a picture. This stuff is nasty. Is there anything else I can do to help get rid of this? Will it spread?

I have grown hollyhock in that location for several years from last years seeds. I usually just have to remember to stake them. This is the first sign of problems.
bev

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plantenthusiast Montreal, QC(Zone 5a) Apr 13, 2008

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.

Thumbnail by plantenthusiast
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