I am no longer specifying knock out roses for commercial landscapes…or I should say, I am severely limiting their use. Yes, they are beautiful, but they have become so popular that their very popularity is putting them at risk. Over use in urban and suburban landscapes are putting not only the knockout roses at risk, but all other rose varieties at the same time.
I’m talking about rose rosette virus. I have noticed that the knockout roses in many commercial settings are hosts to the dreaded and incurable rose rosette virus. This disease first came to my attention back in about 2004 when a new municipal bed that had been planted with over 40 knockout roses had to be dug up and replanted. After that I kept my eye out for roses with rosette virus in commercial settings.
I started noticing them in A LOT of places, the McDonalds landscape near me, the supermarket parking lot, in the parking lot near my bank, at the entrances to subdivisions. Whenever possible I would notify the business and property managers of these businesses that it would be the responsible practice to have the infected roses removed ASAP and destroyed because the virus spreads easily through air borne mites, which endangers all the surrounding landscape roses. This means that the disease on the roses in one parking lot will spread to those in an adjacent commercial lot, and then on to the residential landscapes, etc.
Unfortunately, most commercial property managers do not seem to care or respond, even with repeated notifications of the rose virus over periods of years…yes, I said years! The roses just stay there looking sicker and sicker and more deformed, because, well, they aren’t dead…yet…and in fact, more and more roses were being planted in these very same areas. I even had a property manager tell me that they were in the process of planting hundreds more knock out roses. I suggested that maybe they should choose another species so they don’t invest so heavily in one type of plant in case the virus spread from their infected roses to their new roses, and the property manager just replied that they liked them, and the rose virus didn’t seem to kill them right away, so they were going to leave them in place, and plant more.
So, after having my own beautiful knockout rose hedge for almost 10 years, which is over 8 feet tall and gorgeous, but is also just 2 miles from this particular commercial complex, I am now scheduled to have them removed and burned…because guess what?!?!? They now have the rosette virus too.
I am also aware that even when some of these landscape maintenance crews remove the diseased roses, they are composting them instead of burning them, which compounds the problem even more, because that compost, which is usually then given to municipalities or sold to unsuspecting homeowners, is now contaminated with rose rosette virus. Most of the landscape maintenance crews I have asked about rosette virus don’t know what it is, or how to identify it, or how to properly dispose of diseased roses.
In conclusion, I believe the professional landscape designer should refrain from creating more commercial landscapes featuring knock out roses (or other shrub and landscape rose cultivars) to help curb the spread of this horrible horticultural menace, the rose rosette virus!
by Mary Francois Deweese – Landscape Architect and Founding Principle, Acorn Landscapes, St. Louis, Missouri