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Roses

Are Knock Out roses really the easiest roses to grow?

June 23, 2015

Knock Out Roses

Actually, Knock Out roses are akin to hit movies — they are showing everywhere, there are many “sequels” and they are even spawning merchandise capitalizing on their name. Resistant to black spot, these roses have a long blooming season, without the need for deadheading. They are relatively heat and cold tolerant, making them admirable performers in much of the United States. That said, they are shrub roses, not a new species, and benefit from the same care as other shrub roses, such as proper planting, fertilizing and annual pruning.

The first Knock Out rose, bred by William Radler, received an All American Rose Selection award in 2000. A whole family of other Knock Out roses — a double red, pink single, pink double, as well as Blushing, Rainbow and Sunny varieties now join the cherry–red, single-flowered original. These may differ in some ways besides flower form and color. The yellow Sunny Knock Out, for example, is the only fragrant Knock Out rose, and may get a little taller than its relatives.

Although Knock Out roses are black-spot resistant, Arkansas Cooperative Extension Service researchers report them susceptible to less familiar rose diseases, such as rose Cercospora leaf spot, which causes leaf yellowing and premature leaf drop. With the arrival of rose rosette disease to North Carolina, many Knock Outs have succumbed, perhaps because they are used in many home landscapes, as well as in mass plantings, making it easier for mites to spread this viral disease.

If the Knock Outs have given you courage to grow roses, branch out and make your landscape your own! If you want low maintenance, look for other varieties that do well without extra care. These include many older rose varieties, such as the small rose “The Fairy,” shrub roses, such as “Care-free Beauty” and even large climbers, such as “New Dawn.”

Give any rose at least six hours of sun in soil with a pH of at least 5.5; don’t overdo lime. Fertilize with balanced fertilizer from early spring to August. Keep watered and mulched. Prune your roses in early spring, removing dead, diseased or crossing shoots.

Article written by Debbie Green, Extension Master Gardener Volunteer.

For more information about rose care see:

http://content.ces.ncsu.edu/roses-for-north-carolina/

For more information about rose rosette disease:

http://ncsupdicblog.blogspot.com/2012/08/rose-rosette-hits-close-to-home.html

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Categories Roses Tags knock-out roses, rose rosette, roses

Rosette Disease Knocks Out Roses

May 20, 2013

Rose Rosette Disease
Rose Rosette Disease

The deadly rose rosette disease (RRD) is already making itself known in our wild and ornamental rose population, including Knockouts.  Symptoms vary with the type or species of rose,  but generally include small shoots, off color new growth with smallish leaves,  or a combination of unusual growth or discoloration in any part of the plant, including flowers and thorns. On hybrid teas and some tea roses,  the new growth may be lime-colored. The shoots may also have many small thorns such that the stems appear almost “furry”.

Some herbicides can also cause the witches brooms, distorted growth, and discoloration, but they do not cause the prolific production of thorns. In addition, chemical injury would probably appear on all the roses or broad-leafed plants in the area, whereas rose rosette will generally show up first in just one rose bush.

This contagious disease is transmitted by microscopic wingless eriophyiid mites.  Eliminating rose rosette through mite control has not been shown to work with any consistency. Insecticides are not appropriate and would be a threat to valued pollinators.

Unfortunately, although RRD does not cause the immediate death of infected plants, it cannot be cured or salvaged.  However, the disease may be prevented from spreading by completely removing suspect roses including all the roots.  Any root or plant material not removed could play host for future problems.  Do not put the plant debris in the compost.

It’s speculated that RRD came into the country with the Multi-flora rose which is very susceptible to the disease, showing some of the symptoms as described. That’s another reason to make a survey and encourage the eradication of invasive Multi-flora from your neighborhood.

Article written by Alison Arnold, Extension Agent, Agriculture, Consumer Horticulture, Master Gardener Volunteers.

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Categories Plant Diseases, Roses Tags herbicide damage, knock-out roses, many small thorns, multi-flora rose, rosette disease, wild rose, witches broom

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