How do I treat rust spots on hollyhock.
By Seawillow
United Kingdom 
I have an almost black hollyhock which has rust on the leaves every year. The flowers are beautiful but the leaves are covered in rust spots.
16 Jul, 2009
Answers
I'm growing the black hollyhock this year too, and ours are exactly the same; must be especially vulnerable. There is a variety of hollyhock (common pinkish thing) which is resistant, but that doesn't help when you want something different.
I would guess that as rust is a type of fungus, the only answer is a regular spraying with a fungicide. I've been told that horsetail infused in water for some time makes a great fungicide, so I might try this on our hollyhocks and see if it makes any difference.
I'll let you know in due course!
16 Jul, 2009
I seem to have almost completely rust free hollyhocks this year. I asked a sage at my local garden centre who recommended spraying with stuff called Dithane Protective Fungicide (made by Bayer - www.bayergarden.co.uk). Too late for this year though as you need to spray fortnightly at the very first sign of leaves. I spray both sides of the leaves too. Not sure it works if the rust is already established on the leaves. It can be used for black spot, etc., on roses too - but I only did that once as it left the hollyhocks unblemished but left
a semi permanent powdery mark on the rose leaves. The Dithane also works brilliantly on peach and nectarine plants. You spray those in November and February and not a sign of peach leaf curl.
16 Jul, 2009
Once its in soil, its there for good! Best bet is to spray right form the start of the plants growth, remove any infected leaves off the plants and from off the soil asap, and sterilise gardening tools etc. The early wet weather didint help and the spores are splashed down intot the soil everytime it rains so there is not much that can be done!
There are some rust-resistant varieties of this old-fashioned cottage garden flower. You could try an Alcea ficifolia hybrid. One of them, the Alcea 'Antwerp Mix' T&M do from seed. There not 100% rust free but suffer no where near as badly as norm hollyhocks and dont look manky and leaf less. Ive grown some this year as rust is every so slightly around the area i live as we all have thme in our front garden, spread from neighbour to neighbour!
Antwerp are the more darker colours, rusty red, blcak, orange, reddy, darkish yellow- if possible). but worth it
16 Jul, 2009
If find it best to remove leaves and then at the flowering season has finished, dig up and bin the affected plants. I know spores in soil but it saves the manky plant festering over winter and then it only throwing a few shaort 'not worth it' flower spikes!
But seedlings come up all over place.
16 Jul, 2009
Thank you for your replies. At present the rust problem only affects this hollyhock and has not appeared on any other plants in the garden. It has been in the garden for about 3 years. I will try your remedies first as it is such an unusual colour, but it may be destined for the incinerator if it persists!
19 Jul, 2009
I'm still intrigued by the Horsetail infused in water method!
19 Jul, 2009
As long as there arent any bit of horse tail in water or else you'll just spread it around!
20 Jul, 2009
Horsetail has got to have SOME use. I think God probably created it on April 1st! I'm trying to convince myself it looks attractive as there's no way to get rid of it.
I'm going to make some spray with it next year and conduct trials on peach leaf curl, blight, and hollyhock rust, and see if there is any effect!
22 Jul, 2009
Equisetum hyemale is not invasize but anything Equisetumy i dont trust! evil stuff!
23 Jul, 2009
Such a pain, hollyhock rust, that I actually removed the same one you've got after two years - couldn't keep the rust under control and it seemed to spread it to other plants too. I shall be watching responses to this with interest in case there's a solution!
16 Jul, 2009