Knockout roses are an ever-blooming rose developed by Texas A&M University to withstand extreme Texas growing conditions such as drought, freezing temperatures and high humidity. Their popularity has spread as knockout roses are used in commercial and private landscapes with low maintenance requirements. Knockout roses generally are care free, but occasionally, especially between blooming periods, old flowers, battered foliage and a few dead limbs can make the knockout rose bush look like it's seen better days.
How to Revive Knockout Roses
Remove weeds from around your knockout rose bush as far as 36 inches from the plant so that you can identify any weak or diseased limbs and see how to shape the plant. Also, rake old leaves and other garden debris from around the base of the plant.
Prune out dead wood by cutting dead branches back to the point where they meet a main stem or point of origin. If the dead limb goes all the way to the ground without meeting a main stem, prune it at ground level.
Shape the plant by removing spent flowers and unruly growth by cutting limbs at a 45-degree angle and 1/4 of an inch above an outward facing bud to train new growth outward. You can remove as much as half of a knockout rose bush when pruning, but severe pruning will delay the next blooming period for several weeks. This is because the plant blooms on new wood and requires a longer recovery period.
Gently work two shovels of well-composted manure or compost into the top inch of the soil around the roots, and apply a rose fertilizer according to the instructions on the package. Spread fertilizer just outside the root zone, not on top of the root zone, as it will burn new roots that are close to the surface. Wate the compost and fertilizer well.
Apply a two-inch deep layer of mulch around the base of the plant and six inches past the root zone. Leave a one-inch space between the mulch and the trunk of the knockout rose to prevent mildew from spreading to the bush as the compost decays. Keep it evenly moist until new growth appears.