Q.knockout rose bushes bloom and then turn color
Last year 3 of my knock out rose bushes did not bloom, then this year they grew out from the bottom and the blooms are a very deep red. My friend also had this problem and they are also a deeper red, almost burgundy color. What caused this? Part of them grew out from the bottom and are a deeper color a burgundy color, 2 of them were the trees, and my friend has a tree that has done the same thing and is the deeper color also, very disappointed.
It sounds like the desired upper part of the rosebushes have died, the Knockout roses parts. What you are seeing bloom now is a hardier root stock that the upper knockout rosebushes were grafted to. This happens from time to time. The upper part of the rosebush dies and the hardy rootstock takes over. The growth coming out low like you mentioned is a classic sign that this is what has happened. Here are some articles for you on this subject: https://www.gardeningknowhow.com/ornamental/flowers/roses/own-root-roses-grafted-roses.htm