No knock rose bushes

Asked April 6, 2020, 6:28 PM EDT

I have 5 rose bushes that I planted 3 yrs ago. First 2 years healthy bushes with beautiful flourishing blooms, This year 2 of the bushes are partially blooming but 1/2 of the Bush Is dead from the ground up. What do you suggest I do? I have Miracle Grow stakes for shrubs. Is that a suggestion to put in the ground around rose bushes? I always appreciate your recommendations. Thank you!

Baltimore County Maryland

1 Response

While the Knock Out series of roses are resistant to several common rose diseases, they are still vulnerable to a few ailments and weather-related damage. Stems that have not broken dormancy along with the rest may be suffering from tissue damage from which they will not recover; you can prune off dead wood any time it is found. Make a cut just above a bud (about a quarter inch) to avoid dieback of the stub left behind. If an entire stem is dead, cut it back as far as possible without damaging the main stem or graft.

Shrub roses are best cut back each winter (around late February or early March) to rejuvenate them and encourage vigorous new growth which will flower well. About 18" to 24" off the ground, all growth can be pruned off, and any slender stems the width of a pencil or less can be removed entirely as well. Make sure major stems are facing away from each other (in other words, not crossing and rubbing) to avoid wounds to tissues that can get infected.

Although roses are considered by many gardeners to be "heavy feeders," they won't necessarily need heavy doses of fertilizer to thrive. Proper growing conditions - full sun, good air circulation from not crowding them, and well-drained soil that can be watered during drought - are of the greatest importance in maintaining healthy plants. Nutrient deficiencies tend to manifest in specific ways, often on foliage, and it is uncommon for our soils to be deficient in major nutrients involved in flower production. More often than not, a problem with root health or other environmental factors is the reason for a deficiency seen in above-ground growth, rather than too few nutrients in the soil.

These roses could have suffered some root loss from last spring's exceptionally wet weather followed by late-season drought. Stressed plants are less able to tolerate typical winter conditions and dieback of stems may have resulted, even given the relatively mild winter we experienced.

For now, we suggest just cutting off the dead canes (stems) and observing the plant's growth for signs of other issues. Aphids can feast on emerging rose leaves and are one of the first pests to make an appearance; they can target stressed plants before vigorous ones. Aphids can be easily squished with fingers or squired off with strong water pressure from a hose. Hold off on fertilizing until more obvious signs of nutrient deficiency appear. We find that fertilizers applied dry (granular, where they can be sprinkled evenly around a plant) or wet (diluted in water from a concentrate and watered-in) are easier to use than spike-type fertilizers, which concentrate everything into a small area. Some roots may get overwhelmed with nutrients (which is damaging) while others are unable to access them. Dispersal through the root area of a spike-applied fertilizer can be lengthy if deficiencies need more urgent attention.