Well, there are few people that haven’t heard about Knock Out Roses and their great flowering and low care attributes. One thing that I’ll make clear is that this is one fast growing and aggressive flowering shrub beginning its blooming in mid spring and lasting thru fall right up to frost.
What many people understand this, they do not realize that Knock Outs go thru what I call bloom cycles varying on their nature of care. If not pruned regularly, it’s common for Knock Out Roses to bloom extremely heavy for a month or so and then go thru somewhat of a resting or heavy bloom development preparing for their next heavy blooming cycle again. I recommend that Knock Out owners use this “resting” period as a time to both prune and fertilize to give them the boost and cleaning needed to keep your Knock Out roses looking great. Now pruning can take on a lot of variations depending on each gardener’s preferences and how often they choose to work with their Knock Out roses.
For those who don’t want to spend a lot of time on this type of care, a heavy shearing by reducing the overall rose by 15-20% can be done not performing much selectivity on the pruning. This will shape and provide some uniformity within masses of roses and will clean off a lot of old bloom pods which don’t always look great on the rose. For those who want to and don’t mind spending more time on more timely and selective pruning and dead heading old flowers, this can be done to provide pretty much the same advantages but will usually keep the plant from looking as much like it was shear pruned leaving some natural growth habits and light flowering. Done more often, selective pruning will not show as much of a dramatic span between flowering habits. At the end of May, my Knock Outs had been blooming extremely heavy since mid to late April and had just about completely bloomed out leaving only a few new blooms and buds soon to open. Since my busy schedule doesn’t always allow me to manage weekly clean up and pruning, I chose to prune quite heavy reducing appx. 25% of the roses size leaving only new small buds beginning to develop. I have found that the harder you prune, the faster they grow and generate that new blast of color that we all like about Knock Outs. 
Also, don’t forget to fertilize these Roses every 4-6 weeks usually during these pruning and clean up intervals. I personally suggest you to apply Fertilome Rose Food, Espoma Rose Food, or Mills Magic Rose Fertilizer. These are 3 high quality results proven formulas that will provide consistent nutrients as watering and rainfall carries through to the root system. I suggest that forms of liquid water soluble fertilizer be used as supplements in between granular applications as they do not seem to provide as long lasting of a benefits and are great nutrient boosters to a granular based program.
OK … to prune or not to prune … that is the question. Like most things, the more you put into your Knock Outs, the more you will get out of them. Still know that these are the most popular category of low care roses that you’re experience and you will never regret adding these to your landscape gardens.
Something that we are experimenting with is the once per year application of Fertilome’s Tree & Shrub Systemic Drench insecticide to control pest with emphasis of the Japanese Beetles during their periodic reign. Water your roses with this soil drench insecticide for a season long insecticide treatment that I have been finding beneficial for controlling Japanese Beetles and many other pest.
