How to Prevent Rust Colored Spots on Hollyhocks
The tall spires of Hollyhocks add drama to any flower border, but this pretty, old-fashioned flower often develops an unsightly fungal disease called rust in midsummer. Rusty brown, fuzzy spots appear on both the lower and upper parts of the leaves and stems. In severe cases, leaves and flowers may drop from the plant. The best way to deal with rust is to undertake several preventative steps. Here's what to do. Does this Spark an idea?
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Instructions
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Hollyhock rust is caused by a specific fungus named Puccinia malvacearum. This fungal disease's preferred host plants all belong to the Malvaecae family, which includes several other garden favorites, including hibiscus, rose mallow (lavatera) and flowering maples (albutilon).
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The key to preventing rust (and any fungal disease) is to keep the foliage of your plants as dry as possible, because rust spores need a wet leaf surface in order to germinate. Increase air circulation by staggering the plants and spacing them 24 inches apart on all sides. Water at the base of the plants, being very careful not to spray the leaves as you move the water wand from plant to plant. Even better, use a soaker hose to water. These hoses deliver a slow, steady supply of water to the plants' roots and never get the leaves wet. Also, water in the morning, that way sunshine can quickly dry out any leaves that get wet.
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Keep the base of the plants well weeded and apply a 3-inch mulch of shredded leaves or grass clippings. The mulch will help prevent rust spores that live in the soil from splashing up onto the plants during a rainstorm or when you water.
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If rust does develop on your plants, remove the infected plant immediately and dispose of it in the trash to prevent the problem from spreading. In the fall, cut back the stalks of healthy plants and remove as much dead plant matter as possible from the plant, because the rust spores overwinter on stems and leaves. Burn or trash the stalks and clippings, don't put them in your compost.
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Comments
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my hollyhocks have already started to develop the rust---last fall I did cut back the foliage in hopes of preventing the problem this year, but apparently without luck...so now what? Do I just dig them up and destroy them? At this point, I am certainly prepared to do that and just give up on growing hollyhocks, since this is the 3rd year with the problem--makes them so ugly--so I suppose I should just give up on them, despite their beauty when healthy....
