knockout rose bushes
This summer (in Vermont) was not a good one for my knockout rose bushes. I pruned them back to about 1/3 their previous year's growth, and as the summer progressed, they became very leggy and spindle-like, and the flowers were small. They also may have been bothered by japanese beetles. What is the life expectancy of these roses, and do you have any recommendations for me to follow for next year? Thanks.
I have had Knock-Out roses for at least 10 years and they are going strong in zone 5b/6. In early spring, I prune them way back - down to 18 inches or so - and thin the number of canes to keep the rose open to air circulation and sun penetration. By mid-summer, they are 4 ft tall. Remove dead, diseased and damaged canes to the base of the plant. Canes should be solid green. Mine get lots of bright sunlight, fertilizer as recommended on the container and visual inspection regularly. Rose slugs were a real problem this spring and they showed up again in Sept. When spotted and removed early, the damage they cause is limited. It's the same with Japanese beetles. I've linked to articles on rose slugs and pruning.