Since being put on the market in 2000, 8 varieties of knockout roses have been developed. These grow in shrub form and are low maintenance. Most importantly, they are extremely disease resistant. The bushes can grow anywhere between zone 5b and 9. The do best in full sun, but tolerate light shade if properly taken care of. They can flower from Spring to Fall and, while they can get up to 6 feet tall and 6 feet wide, they can be pruned back for a smaller shape if desired.