Q.Do Knockout Roses Have A Limited Lifespan?
My knockout roses are 9 years old. For 6 years the bushes were beautiful. The last 2 years the bushes have been struggling. I have fertilized, and used other recommended treatments for roses but the bushes remain thin. They are still producing flowers but the foliage is thin. Do knockout have a limited lifespan?
I have not heard of a life span on the Knock Outs. Mine have been going strong for 6 going on 7 years. I do suggest doing a hard rejuvenating pruning on them though. Prune the back in the late fall, once they have gone dormant. Pruning the back more than any you have done before. In early Spring when they first start to leaf out, water them with some water that has both a product called Super Thrive and a Root Stimulator product in it, such as Fertilome Root Stimulator. Water them with a fresh batch of this mix the next 5 to 6 times they need watering. Also give them a good organic rose food that will build their soils home and feed them, such as this one: https://www.arbico-organics.com/product/down-to-earth-rose-and-flower-mix/Organic-Fertilizer
I also recommend giving each of them a cup of Kelp Meal mixed into the soils. They love that!