Q: My “Sum and Substance” hosta plants have developed some strange mottled colors on the leaves. Is this a disease problem or a plant mutation?
— Henry Sims, Highland Park
A: Hostas have a great reputation for being relatively pest- and disease-free and easy to grow. Gardeners have historically been able to buy and trade hostas without concern for introducing any problems to their gardens.
However, a virus called Hosta Virus X is becoming more common. Hostas are the only known plant to be infected by this virus. Hosta Virus X-infected plants will not recover, so it is important to remove affected plants immediately to avoid spreading the disease to other hostas in your garden.
Dig up the plant with as many of the roots as possible and discard in the trash or burn it. Do not put it in the compost.
The virus can only reproduce inside living hosta cells; it was originally believed it could not survive in the soil after infected roots had decomposed. However, recent research suggests otherwise, so it will be best to replace the infected hosta with a plant other than a hosta.
Hostas may not show symptoms of this disease for a year or more after being infected. The symptoms can vary among the different cultivars, which have different leaf textures and coloration. Look for stunted growth, distorted leaves and distortions of the normal leaf color. For example, a light-colored leaf, such as the lime-green to chartreuse leaves of “Sum and Substance,” might show blue or darker green splotches that follow the leaf veins and bleed out into surrounding tissue. A dark-leaved hosta, such as Hosta sieboldiana “Elegans,” may appear as if bleach has been spilled on it.
The leaf tissue of infected plants often appears lumpy, puckered and of a different thickness or texture than healthy plants, but this is very difficult to discern on hostas that have heavily textured leaves. Cold damage and light frost also can cause damage that appears similar to Hosta Virus X.
For help in diagnosing your hosta’s problem, contact the Plant Information Service at chicagobotanic.org/plantinfoservice or 847-835-0972. A laboratory test can confirm the presence of the virus.
Though insects spread many plant viruses, they are not the culprit in this case. Hosta Virus X is most commonly spread by people. It can be transmitted by any type of mechanical injury that moves plant fluids. For example, it can travel from one plant to another on pruning tools when they are used to snip off old leaves or flower stalks. It also can be spread by string trimmers, mowers, shovels and even your hands, if they are contaminated with sap from virus-infected plants. Be sure to disinfect your tools frequently with rubbing alcohol or Lysol disinfectant while you are working with hostas.
Some research suggests that Hosta Virus X is most easily transmitted in the spring when hostas are actively growing and is more difficult to transmit after a hosta blooms. That means that late summer and fall may be the safest time to dig and divide plants to minimize the potential to spread the virus.
With careful observation and good garden management practices, there is no reason to stop buying and growing hostas.
Tim Johnson is director of horticulture for the Chicago Botanic Garden in Glencoe (chicagobotanic.org). Send questions to: Gardening Q&A, Sunday, Chicago Tribune, 435 N. Michigan Ave., Chicago, IL 60611-4041; e-mail to
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